0001193125-26-374729 | S-1 | XBRL Viewer | Obsidian Therapeutics INC

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Stock-Based Compensation - Summary Of The Fair Value of the Stock Options (Details) - $ / shares	6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Risk-free interest rate	3.94%	4.26%	3.94%	4.25%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected term (in years)	5 years 10 months 24 days	6 years	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility	82.71%	106.25%	89.54%	133.20%
Minimum [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Fair value of common stock	$ 0.78	$ 0.78	$ 0.78	$ 1.01
Maximum [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Fair value of common stock	$ 0.96	$ 1.13	$ 1.13	$ 1.13

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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+ Details

Summary of Significant Accounting Policies

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). In our opinion, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the financial position and results of operations for the reported interim periods. We consider events or transactions that occur after the balance sheet date but before the condensed consolidated financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. These unaudited interim condensed consolidated financial statements should be read in conjunction with the consolidated financial statements, including the related notes thereto, for the year ended December 31, 2025.

There were no changes to the Company’s significant accounting policies during the six months ended June 30, 2026, other than noted below.

Deferred Offering Costs

The Company capitalizes legal, accounting, and other professional fees directly related to the Concurrent PIPE Financing (as defined below) and merger, which are recorded within prepaid expenses and other current assets on the condensed consolidated balance sheets and are expensed or charged against additional

paid-in

capital, as applicable, upon closing of the merger transaction and Concurrent PIPE Financing.

Recently Issued Accounting Standards Not Yet Adopted

In November 2024, the FASB issued ASU

2024-03,

Income Statement–Reporting Comprehensive Income–Expense Disaggregation Disclosures (Subtopic

220-40):

Disaggregation of Income Statement Expenses

, or ASU

2024-03

which requires public business entities to disclose specified information about certain costs and expenses on an interim and annual basis. ASU

2024-03

is effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027, with early adoption permitted. Obsidian Sub is currently evaluating the impact that adoption of ASU

2024-03

will have on its consolidated financial statements and related disclosures.

In December 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”)

No. 2025-12,

Codification Improvements, which includes amendments to Accounting Standards Codification, or ASC, 260, Earnings Per Share. The amendments clarify guidance related to the calculation of diluted earnings per share when an entity reports a loss from continuing operations, including the evaluation of the effect of potential common shares. ASU

2025-12

is effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods within those annual periods, and are required to be applied retrospectively. Early adoption is permitted. The Company is currently evaluating the impact of ASU

2025-12

on its consolidated financial statements and related disclosures.

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP as found in the Accounting Standards Codification (“ASC”) and as amended by Accounting Standard Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”).

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, expenses, and disclosures. Significant estimates and assumptions reflected in these financial statements include, but are not limited to, research and development expenses, fair value of common stock and any resulting equity-based compensation expense, and income taxes. The Company evaluates its estimates and assumptions on an ongoing basis. All revisions to accounting estimates are recognized in the period in which the estimates are revised and in any future periods affected. Actual results could differ from the Company’s estimates.

Cash and Cash Equivalents

The Company considers all highly liquid investments that are readily convertible into cash with original maturities three months or less at the time of purchase to be cash equivalents. Cash equivalents are stated at fair value.

Marketable Securities

Marketable securities consist of U.S. treasuries with maturities greater than three months. The Company classifies all of its marketable securities as available for sale based upon its intent with regard to such investments. The Company classifies marketable securities as short term when their remaining contractual maturities are one year or less from the balance sheet date, and as long term when the marketable security has a remaining contractual maturity of more than one year from the balance sheet date.

The amortized cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income. Dividends are also included in interest and other income.

The Company periodically reviews its investments for impairment based on a security-specific analysis as of each balance sheet date. If the fair value of a security is below its amortized cost, the Company first assesses whether it intends to sell the security or is more likely than not required to sell it before recovery of its amortized

cost. If neither condition is met, the Company evaluates whether a portion of the decline is attributable to credit loss. Any credit-related impairment is recorded as an allowance for credit losses through earnings, with

non-credit-related

unrealized losses recorded in other comprehensive income (loss). The Company did not recognize any credit loss relating to its investments for the years ended December 31, 2025 or 2024.

Segment Information

The Company manages its operations as a single segment for the purpose of assessing performance and making operating decisions. The Company is developing therapeutic treatments for cancer-related diseases. The Company has determined that its chief operating decision maker is its Chief Executive Officer. The Company’s chief operating decision maker reviews the Company’s financial information on an aggregated basis for purposes of allocating resources and assessing financial performance. All of the Company’s tangible assets are located in the United States and all of the Company’s historical collaboration revenue was derived from its collaboration partners headquartered in the United States.

Concentration of Credit Risk and of Significant Suppliers

Financial instruments that potentially expose the Company to concentrations of credit risk consist of cash, cash equivalents, and marketable securities. The Company limits its exposure to credit loss by placing its cash with major financial institutions and invests only in short-term obligations. The deposits, at times, may exceed federally insured limits. The Company has not experienced any losses in such accounts. The Company has no significant

off-balance

sheet concentrations of credit risk such as foreign exchange contracts, option contracts or other foreign hedging arrangements.

The Company is dependent on third-party manufacturers to supply certain products for research and development activities in its programs. Certain key raw materials can be difficult to acquire on a consistent basis. If the Company cannot access adequate supply sources its programs could be adversely affected by an interruption in the availability of these raw materials.

Restricted Cash

The Company has restricted cash in the form of letters of credit which are held in interest bearing money market accounts as collateral for the Company’s Cambridge, Massachusetts, and Bedford, Massachusetts leases. The Company has classified both money market accounts collateralizing the letters of credit issued as long-term restricted cash on its consolidated balance sheets as the remaining term of each lease exceeds twelve months as of December 21, 2025 and 2024.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset, as follows:


		Estimated Useful Life
Laboratory equipment		5 years
Leasehold improvements		Shorter of the lease term or estimated useful life
Furniture and fixtures		5 years
Computer software		3 years

Maintenance and repairs are charged to expense as incurred. When assets are retired or otherwise disposed of, the cost of these assets and related accumulated depreciation or amortization are eliminated from the consolidated balance sheets and any resulting gains or losses are included in the consolidated statements of operations in the period of disposals.

Impairment of Long-Lived Assets

Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated. Impairment charges are recognized at the amount by which the carrying amount of an asset exceeds the fair value of the asset. There were no impairments for the years ended December 31, 2025 or 2024.

Leases

In accordance with ASU

2016-02,

Leases

(“ASC 842”), the Company determines whether an arrangement is or contains a lease at inception. A contract is or contains a lease if the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration. The Company classifies leases at the lease commencement date, when control of the underlying asset is transferred from the lessor to the lessee, as operating or finance leases and records a right of use (“ROU”) asset and a lease liability on the consolidated balance sheets for all leases with an initial lease term of greater than 12 months. The Company has elected to not recognize leases with a lease term of 12 months or less, and payments are recognized as expense on a straight-line basis over the lease term.

The Company enters into contracts that contain both lease and

non-lease

components.

Non-lease

components may include maintenance, utilities, and other operating costs. For leases of real estate, the Company combines the lease and associated

non-lease

components in its lease arrangements as a single lease component. Variable costs, such as utilities or maintenance costs, are not included in the measurement of

right-of-use

assets and lease liabilities, but rather are expensed when the event determining the amount of variable consideration to be paid occurs.

Finance and operating lease assets and liabilities are recognized at the lease commencement date based on the present value of the lease payments over the lease term using the discount rate implicit in the lease if readily determinable. If the rate implicit is not readily determinable, the Company utilizes its incremental borrowing rate, which reflects the fixed rate at which the Company could borrow on a collateralized basis over a similar term and amount equal to the lease payments in a similar economic environment. ROU assets are further adjusted for initial direct costs, prepaid rent, or incentives received. Operating lease payments are expensed using the straight-line method as an operating expense over the lease term. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Finance lease assets are amortized to depreciation expense using the straight-line method over the shorter of the useful life of the related asset or the lease term. Finance lease payments are bifurcated into (i) a portion that is recorded as interest expense using the effective interest method and (ii) a portion that reduces the finance liability associated with the lease.

In addition, the Company examines other contracts with suppliers, vendors and outside parties to identify whether such contracts contain an embedded lease and, as applicable, accounts for such embedded leases in accordance with ASC 842.

Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs.

Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

Level 1

- Quoted prices in active markets for identical assets or liabilities.

Level 2

- Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.

Level 3

- Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

The Company’s preferred stock warrant liability is carried at fair value, determined according to Level 3 inputs in the fair value hierarchy described above. The carrying values of the Company’s accounts payable and accrued expenses and other current liabilities approximate their fair value due to the short-term nature of these liabilities.

Redeemable Convertible Preferred Stock

The Company’s redeemable convertible preferred stock is classified as temporary equity in the accompanying consolidated balance sheets and excluded from stockholders’ deficit as the potential redemption of such stock is outside the Company’s control. Costs incurred in connection with the issuance of redeemable convertible preferred stock are recorded as a reduction of gross proceeds from issuance.

The Company did not accrete the carrying values of the preferred stock to the redemption values since the occurrence of either a merger or consolidation; or a sale, lease, transfer, exclusive license or other disposition, in a single transaction or series of related transactions, of all, or substantially all, of the Company’s assets or intellectual property of the Company (a “Deemed Liquidation Event”) was not considered probable as of December 31, 2025 or 2024. Subsequent adjustments of the carrying values to the ultimate redemption values will be made only when it becomes probable that these events will occur. In the event of such a Deemed Liquidation Event, the proceeds from the event are distributed in accordance with the liquidation preferences, provided that the holders of preferred stock have not converted their shares into common stock.

Collaboration Agreements

The Company analyzes its collaboration arrangements to assess whether they are within the scope of ASC 808,

Collaborative Arrangements

(“ASC 808”) to determine whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities. This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. When the Company has concluded that a collaborator meets the definition of a customer the Company follows the guidance in ASC Topic 606,

Revenue from Contracts with Customers

(“ASC 606”).

Revenue Recognition

Under ASC 606, the Company recognizes revenue associated with collaboration agreements when its customer obtains control of promised goods or services in an amount that reflects the consideration that the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies a performance obligation.

The Company assesses the goods or services promised within each contract and determines those that are performance obligations. The Company’s collaboration agreements typically consist of promises to transfer licenses to the Company’s intellectual property, research and development services, and related supporting activities.

The Company assesses whether each promised good or service is distinct for the purpose of identifying the performance obligations in the contract. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services, including the significance of the Company’s integration service, the interdependency of their utility, and the customer’s ability to derive their intended benefit from the contract and whether such are separable from the other aspects of the contractual relationship. Promised goods and services are considered distinct provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer (that is, the good or service is capable of being distinct) and (ii) the Company’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract (that is, the promise to transfer the good or service is distinct within the context of the contract). In assessing whether a promised good or service is distinct, the Company considers factors such as the research, development, manufacturing and commercialization capabilities of the customer and the availability of similar services in the general marketplace. If a promised good or service is not distinct, an entity is required to combine that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct.

When an arrangement includes a customer option for additional goods or services, the Company assesses whether the option provides the customer with a material right. A material right is an option to purchase the underlying goods and services at a price below their standalone selling price that the customer would not have received had it not entered into the initial contract. When an option is deemed to provide a material right to the customer, it is accounted for as a separate performance obligation.

The transaction price is the sum of fixed and estimated variable consideration. Variable consideration is estimated using the most likely amount or expected value method to determine the amount of consideration to which the Company expects to be entitled in exchange for transferring the promised goods or services to a customer. The amount of variable consideration included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At each reporting date, the Company

re-evaluates

the estimate of variable consideration and the constraint.

When arrangements include development and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. Milestone payments triggered by events that have significant uncertainty and are not within the Company’s control such as regulatory approvals, are not considered probable of being achieved until those approvals are received and are excluded from the transaction price.

For arrangements with licenses of intellectual property, where the license is deemed to be the predominant item to which the royalties relate, the Company utilizes the royalty exception and recognizes revenue and sales-based royalties and milestones at the later of (i) when the related sales occur, or (ii) upon satisfaction of the related performance obligation.

In determining the transaction price, the Company adjusts consideration for the effects of the time value of money if the timing of payments provides the Company with a significant benefit of financing. If the expectation at contract inception is such that the period between the transfer of the promised goods or services to the customer and the payment by the customer will be one year or less, the Company will elect the practical expedient provided by ASC 606 to forego this assessment and conclude a significant financing component does not exist.

Variable consideration may be allocated to a single performance obligation or a subset of distinct goods or services within a series performance obligation if the variable consideration is both earned by the efforts or outcomes of transferring the service and the allocation objective it met. The remaining transaction price is allocated to the identified performance obligations in proportion to their standalone selling prices (“SSP”) on a relative SSP basis. SSP is determined at contract inception using an approach that maximizes the use of available inputs and may include the adjusted market assessment or cost-plus margin approach. The SSP estimate is not updated to reflect changes between contract inception and when the performance obligations are satisfied. Determining the SSP for performance obligations may require significant judgment, including consideration market conditions, entity-specific pricing strategies, and observable data points on expected costs and profit margins.

The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when, or as, each performance obligation is satisfied, either at a point in time or over time, and if over time, recognition is based on the measure of progress that most faithfully depicts our performance towards transferring the related goods and services. The estimate of the Company’s measure of progress is updated at each reporting date.

The Company records amounts as accounts receivable when the right to consideration is deemed unconditional. When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer, a contract liability, which the Company refers to as deferred revenue, is recorded.

Research and Development and Manufacturing Contract Costs and Accruals

Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities, including costs for salaries and bonuses, employee benefits, subcontractors, facility-related expenses, depreciation, stock-based compensation, third-party license fees, laboratory supplies, and external costs of outside vendors engaged to conduct discovery and preclinical development activities as well as to begin to manufacture materials for upcoming clinical trials.

Nonrefundable advance payments for goods or services to be provided in the future for use in research and development activities are recorded as prepaid expenses. Such prepaid expenses are recognized as an expense when the goods have been delivered or the related services have been performed, or when it is no longer expected that the goods will be delivered, or the services rendered.

Upfront payments under license agreements are expensed as research and development expense upon receipt of the license, and annual maintenance fees under license agreements are expensed in the period in which they are incurred. Contingent milestone payments are recognized when the related contingency is resolved and the amounts are paid or become payable.

The Company has entered into various research, development and manufacturing contracts with research institutions and other companies. These agreements are generally cancelable, and related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research, development and manufacturing costs. When billing terms under these contracts do not coincide with the timing of when the work is performed, the Company is required to make estimates of outstanding obligations to those third parties as of period end. Any accrual estimates are based on a number of factors, including the Company’s knowledge of the progress towards completion of the research, development and manufacturing activities, invoicing to date under the contracts, communication from the research institutions and other companies of any actual costs incurred during the period that have not yet been invoiced and the costs included in the contracts. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the estimates made by the Company.

Patent Costs

For the periods ended December 31, 2025 and 2024, costs associated with successful and pending applications of patents and trademarks are recognized as general and administrative expenses as incurred.

Stock-Based Compensation

The Company measures stock-based awards granted to employees, nonemployees and directors based on the fair value on the date of the grant and recognizes compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award. Forfeitures are accounted for as they occur. Generally, the Company issues stock-based awards in the form of stock options with only service-based vesting conditions and records the expense for these awards using the straight-line method. The Company has also issued stock-based awards in the form of stock options with both performance and service-based vesting conditions. The Company records the expense for stock-based awards with both performance and service-based vesting using an accelerated attribution method, once the performance conditions are considered probable of being achieved, using management’s best estimates.

The fair value of each share option is estimated on the date of grant using the Black-Scholes option pricing model, which requires inputs based on certain subjective assumptions, including:

•

Fair Value of Common Stock

- Because there is no public market for the Company’s common shares, the Company has determined the fair value of the Company’s common stock based on the independent third-party appraisals. The fair value of the Company’s common stock has been determined using a market approach to estimate the Company’s enterprise value and applies a hybrid method for allocation of equity value to different classes of equity. The hybrid method is a combination of an option pricing method (“OPM”) and a probability-weighted expected return method (“PWERM”) that contemplated the Company’s financial position and historical financial performance, the status of development of the Company’s programs, the current climate in the marketplace, the illiquid nature of the common stock, the effect of the rights and preferences of the preferred stockholders, and the prospects of a liquidity event, among others.

•

Estimated Volatility

—As a private company the Company lacks company-specific historical and implied volatility information for its shares, therefore, the Company estimates its expected share price volatility based on the historical volatility of publicly traded peer companies.

•

Expected Term

—The expected term represents the period that the stock-based awards are expected to be outstanding. The Company uses the simplified method to determine the expected term for “plain-vanilla” options, which is based on the average of the

time-to-vesting

and the contractual life of the options. For awards with both performance and service based vesting conditions, the expected term has been determined using management’s best estimate considering the characteristics of the award, contractual life, the timing of the expected achievement of the performance conditions, and the remaining time-based vesting period, if any. For nonemployees, the Company determines the life to be the contractual term of the option.

•

Risk Free Interest Rate

—The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award.

•

Dividend Yield

—The Company has used an expected dividend yield of zero based on the fact that it has never paid cash dividends on its ordinary shares and does not expect to pay any cash dividends in the future.

The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.

Income Taxes

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies.

The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a

two-step

process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed

more-likely-than-not

to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense. Any accrued interest and penalties are included within the related tax liability. As of December 31, 2025 and 2024, the Company had not accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s consolidated statements of operations.

The rules dealing with U.S. federal, state and local income taxation are constantly under review by persons involved in the legislative process and by the Internal Revenue Service and the U.S. Treasury Department. Changes to tax laws (which changes may have retroactive application) could adversely affect the Company’s stockholders or the Company. The Company assesses the impact of various tax reform proposals and modifications to existing tax treaties in all jurisdictions where the Company has operations to determine the potential effect on its business and any assumptions the Company has made about its future taxable income. The Company cannot predict whether any specific proposals will be enacted, the terms of any such proposals or what effect, if any, such proposals would have on its business if they were to be enacted.

Net Loss Per Share

The Company calculated basic and diluted net loss per share attributable to common stockholders in conformity with the

two-class

method required for companies with participating securities. The Company’s

Preferred Stock (as defined below) is considered to be a participating security as the holders are entitled to receive dividends at a dividend rate payable in preference and priority to the holders of common stock. The

two-class

method determines net loss per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The

two-class

method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period has been distributed. There is no allocation required under the

two-class

method during periods of loss since the participating securities do not have a contractual obligation to share in the losses of the Company.

Under the

two-class

method, basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share attributable to common stockholders is computed

by (i) adjusting net loss attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities and (ii) dividing the diluted net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period, including potential dilutive common shares. For purposes of this calculation, Preferred Stock, preferred stock warrants, and stock options to purchase common stock are considered potential dilutive common shares.

The Company has generated a net loss for each of the periods presented. Accordingly, basic and diluted net loss per share attributable to common stockholders are the same because the inclusion of the potentially dilutive securities would be anti-dilutive.

Other Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders’ deficit that result from transactions and economic events other than those with stockholders. Other comprehensive loss consists of unrealized gains (losses) on marketable securities.

Recently Adopted Accounting Pronouncements

In December 2023, the FASB issued ASU

No. 2023-09,

Income Taxes (Topic 740): Improvement to Income Tax Disclosures

(“ASU

2023-09”),

to enhance the transparency and decision usefulness of income tax disclosures. ASU

2023-09

became effective for annual periods beginning after December 15, 2024 on a prospective basis for public business entities. For all other entities, the ASU is effective for annual periods beginning after December 15, 2025 on a prospective basis. Early adoption and retrospective application in all prior periods presented is permitted. The Company has early adopted and applied the pronouncement on a retrospective basis. The adoption of ASU

2023-09

did not result in a material impact to the consolidated financial statements and related disclosures.

Recently Issued Accounting Standards Not Yet Adopted

In November 2024, the FASB issued ASU

2024-03,

Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic

220-40):

Disaggregation of Income Statement Expenses

(“ASU

2024-03”)

which requires public business entities to disclose specified information about certain costs and expenses on an interim and annual basis. ASU 2024-03 is effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027, with early adoption permitted. The Company is currently evaluating the impact that adoption of ASU

2024-03

will have on our financial statement disclosures.

Nature of the Business and Basis of Presentation	6 Months Ended	12 Months Ended
Nature of the Business and Basis of Presentation	Jun. 30, 2026	Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation Obsidian Therapeutics Sub, Inc. (formerly known as, Obsidian Therapeutics, Inc.) (the “Company” is a clinical-stage biopharmaceutical company harnessing novel protein-regulation technology to develop engineered tumor infiltrating lymphocytes (“TIL”) cell therapies for the treatment of patients with solid tumors. The Company’s proprietary cytoDRiVE ™ platform is highly versatile and allows it to leverage drug responsive domains to control protein function, with its initial focus on TIL cell therapies developed from this platform (“cytoTILs ™ ”). The Company’s lead product candidate, OBX-115, is a novel, genetically engineered, autologous TIL cell therapy currently in a Phase 2 clinical trial for the treatment of advanced melanoma and a Phase 1 clinical trial for the treatment of non-small cell lung cancer. The Company was incorporated in 2015 under the laws of the State of Delaware, and its principal offices are in Cambridge, Massachusetts. Since its inception, the Company has devoted substantially all its efforts to raising capital, obtaining financing, and incurring research and development costs related to advancing its scientific platform. The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Obsidian Therapeutics Securities Corporation. All intercompany balances and transactions have been eliminated. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, and ability to secure additional capital to fund operations. Product candidates currently under development will likely require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure, and extensive compliance reporting capabilities. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s technology will be obtained, that any products developed will obtain necessary government regulatory approval, or that any approved products will be commercially viable. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees and consultants. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. Liquidity The Company has a history of operating losses and negative cash flows from operations and expects to continue generating losses as it advances its research and development programs. As of June 30, 2026 the Company had cash, cash equivalents, and marketable securities of $34.4 million. On April 14, 2026, the Company entered into a definitive merger agreement with Galera Therapeutics, Inc. (“Galera”) pursuant to which both companies were to become wholly owned subsidiaries of a newly formed holding company, Gazelle Parent, Inc. (“Gazelle”). In connection with the merger, Gazelle, the Company and Galera secured commitments for a private investment in public equity financing in Galera with expected gross proceeds of approximately $350.0 million. On July 31, 2026, immediately prior to the completion of the merger transaction and before the issuance of these condensed consolidated financial statements, the Concurrent PIPE Financing (as defined below) closed and generated gross proceeds of approximately $350.0 million. The Company expects that its cash, cash equivalents and marketable securities subsequent to the closing of the Concurrent PIPE Financing will be sufficient to fund its operating expenses and capital expenditure requirements through the next twelve months from the date of issuance of these condensed consolidated financial statements.	1. Nature of the Business and Basis of Presentation Obsidian Therapeutics, Inc. (the “Company”) is a clinical-stage biopharmaceutical company harnessing novel protein-regulation technology to develop engineered tumor infiltrating lymphocytes (“TIL”) cell therapies for the treatment of patients with solid tumors. The Company’s proprietary cytoDRiVE ™ platform is highly versatile and allows it to leverage drug responsive domains to control protein function, with its initial focus on TIL cell therapies developed from this platform (“cytoTILs ™ ”). The Company’s lead product candidate, OBX-115, is a novel, genetically engineered, autologous TIL cell therapy currently in a Phase 2 clinical trial for the treatment of advanced melanoma and a Phase 1 clinical trial for the treatment of non-small cell lung cancer. The Company was incorporated in 2015 under the laws of the State of Delaware, and its principal offices are in Cambridge, Massachusetts. Since its inception, the Company has devoted substantially all its efforts to raising capital, obtaining financing, and incurring research and development costs related to advancing its scientific platform. The consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Obsidian Therapeutics Securities Corporation. All intercompany balances and transactions have been eliminated. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, and ability to secure additional capital to fund operations. Product candidates currently under development will likely require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure, and extensive compliance reporting capabilities. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s technology will be obtained, that any products developed will obtain necessary government regulatory approval, or that any approved products will be commercially viable. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees and consultants. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. Going Concern The Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern for at least one year after the issuance of these consolidated financial statements. As a result of this evaluation, substantial doubt about the Company’s ability to continue as a going concern exists. The Company has a history of operating losses and negative cash flows from operations and expects to continue generating losses as it advances its research and development programs. As of December 31, 2025, the Company had cash, cash equivalents, and marketable securities of $80.5 million and an accumulated deficit of $295.9 million. Net cash used in operating activities was $90.4 million for the year ended December 31, 2025. The Company expects to incur additional losses and negative cash flows from operations over the next several years as the product candidates currently under development will require significant additional research and clinical development efforts prior to commercialization. Based on the Company’s accumulated deficit, current and future expected losses, and current cash flow projections, which exclude any new capital raising activities, management determined that the Company does not have adequate financial resources to fund its forecasted operating costs for at least one year after the issuance date of these consolidated financial statements. Management’s plans to alleviate this uncertainty include pursuing additional equity or debt financing, reducing discretionary spending, and exploring strategic collaborations. However, these plans are not fully within the Company’s control, and there is no assurance that such funding or arrangements will be available on acceptable terms or at all. Because of the uncertainty inherent in these efforts, the Company has concluded that substantial doubt exists with respect to its ability to continue as a going concern for one year after the issuance date of these consolidated financial statements. The consolidated financial statements have been prepared assuming the Company will continue operating as a going concern, and no adjustments have been made to the carrying amounts or classification of assets and liabilities that may be necessary if the Company were unable to continue as a going concern.

Subsequent Events - Additional Information (Details) $ / shares in Units, $ in Millions	Jul. 31, 2026 USD ($) $ / shares	Aug. 03, 2026	Jun. 30, 2026 $ / shares shares	Feb. 28, 2026 $ / shares shares	Dec. 31, 2025 $ / shares shares	Dec. 31, 2024 $ / shares shares
Subsequent Event [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion \| shares				7,085,290
Preferred Stock, Convertible, Shares Issuable \| shares			207,952,902		215,038,192	215,038,192
Preferred Stock, Par or Stated Value Per Share \| $ / shares					$ 0.0001
Common Stock, Par or Stated Value Per Share \| $ / shares			$ 0.0001		$ 0.0001	$ 0.0001
Series A1 Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred Stock, Convertible, Shares Issuable \| shares			26,114,925		33,200,215	33,200,215
Preferred Stock, Par or Stated Value Per Share \| $ / shares				$ 0.0001
Series C Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred Stock, Convertible, Shares Issuable \| shares			84,567,145		84,567,145	84,567,145
Subsequent Event [Member]
Subsequent Event [Line Items]
Common Stock, Par or Stated Value Per Share \| $ / shares	$ 0.001
Percentage Of Proceeds Received By Parent From The Development		80.00%
Percentage Of Proceeds Received By Parent From The Supportive Care Product Divestiture		95.00%
Subsequent Event [Member] \| Parent Company [Member]
Subsequent Event [Line Items]
Common Stock, Par or Stated Value Per Share \| $ / shares	0.0001
Subsequent Event [Member] \| Series A1 Preferred Stock [Member]
Subsequent Event [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion \| shares				7,085,290
Preferred Stock, Convertible, Conversion Ratio				1
Preferred Stock, Convertible, Shares Issuable \| shares				7,085,290
Subsequent Event [Member] \| Series C Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred Stock, Par or Stated Value Per Share \| $ / shares	$ 0.001
Payments for Repurchase of Preferred Stock and Preference Stock \| $	$ 350.0

Stock-Based Compensation - Summary of the Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Number of Options, Outstanding Beginning	38,061,610	40,628,032
Number of Options granted	5,353,691	432,000		1,231,034
Number of Options exercised	(1,161,144)	(20,146)
Number of Options forfeited	(2,441,148)	(2,530,814)
Number of Options expired	(4,177,316)	(447,462)
Number of Options Outstanding Ending	35,635,693	38,061,610	40,628,032
Number of Options Vested and exercisable	21,465,199	23,056,967
Number of Options Unvested	14,170,494	15,004,643
Weighted-average exercise price per share Outstanding Beginning	$ 0.77	$ 1.03
Weighted-average exercise price per share granted	0.79	0.78
Weighted-average exercise price per share exercised	0.72	0.97
Weighted-average exercise price per share forfeited	0.78	1.05
Weighted-average exercise price per share expired	0.77	1
Weighted-average exercise price per share Outstanding Ending	0.78	0.77	$ 1.03
Weighted-average exercise price per share Vested and exercisable	0.77	0.77
Weighted-average exercise price per share Unvested	$ 0.78	$ 0.78
Weighted-Average Remaining Contractual Term (in years)	7 years 4 months 24 days	6 years 10 months 24 days	8 years 4 months 24 days
Weighted-Average Remaining Contractual Term (in years) Vested and exercisable	6 years 8 months 12 days	6 years 1 month 6 days
Weighted-Average Remaining Contractual Term (in years) Unvested	8 years 2 months 12 days	8 years 2 months 12 days
Aggregate Intrinsic Value Outstanding Beginning	$ 298	$ 4,146
Aggregate Intrinsic Value Outstanding Ending	6,528	298	$ 4,146
Aggregate Intrinsic Value Vested and exercisable	4,045	298
Aggregate Intrinsic Value Unvested	$ 2,102	$ 0

Common Stock	6 Months Ended	12 Months Ended
Common Stock	Jun. 30, 2026	Dec. 31, 2025
Stockholders' Equity Note [Abstract]
Common Stock	6. Common Stock The Company’s fourth amended and restated certificate of incorporation authorizes the Company to issue 274,320,131 shares of common stock. As of June 30, 2026, the Company had reserved 207,952,902 shares of common stock for the conversion of the Preferred Stock (Note 5), as applicable.	7. Common Stock The Company’s fourth amended and restated certificate of incorporation authorizes the authorizes the Company to issue 274,320,131 shares of common stock. As of December 31, 2025, the Company had reserved 215,060,316 shares of common stock for the conversion of the Preferred Stock (Note 6), as applicable. The holders of shares of common stock are entitled to one vote for each share held with respect to all matters voted on by the stockholders of the Company. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors, subject to the prior rights of holders of all classes of stock outstanding. In a Deemed Liquidation Event, after the payment in full of all preferential amounts required to be paid to the holder of shares of Preferred Stock, the holders of the then outstanding common stock are entitled to receive that portion of the remaining funds to be distributed to holders of common stock.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 20
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 20: http://www.xbrl.org/2003/role/disclosureRef
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Reference 23: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 8A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-8A

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478448/946-505-50-6

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-6

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 35: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-16

+ Details

Financial Instruments and Fair Value Measurements (Table)

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following tables present information about the Company’s financial assets and liabilities that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy used to determine such fair values (in thousands):


	Fair Value Measurements at June 30, 2026
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	17,733	$	—	$	—	$	17,733
U.S. Treasuries		—		16,462		—	$	16,462

Total assets	$	17,733	$	16,462	$	—	$	34,195

Liabilities:
Preferred stock warrant liability	$	—	$	—	$	1	$	1

Total liabilities	$	—	$	—	$	1	$	1


	Fair Value Measurements at December 31, 2025
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	39,905	$	—	$	—	$	39,905
U.S. Treasuries		—		40,081		—		40,081

Total assets	$	39,905	$	40,081	$	—	$	79,986

Liabilities:
Preferred stock warrant liability	$	—	$	—	$	3	$	3

Total liabilities	$	—	$	—	$	3	$	3


	Fair Value Measurements at December 31, 2025
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	39,905	$	—	$	—	$	39,905
U.S. Treasuries		—		40,081		—		40,081

Total assets	$	39,905	$	40,081	$	—	$	79,986

Liabilities:
Preferred stock warrant liability	$	—	$	—	$	3	$	3
Total liabilities	$	—	$	—	$	3	$	3


	Fair Value Measurements at December 31, 2024
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	49,733	$	—	$	—	$	49,733
U.S. Treasuries		—		118,509		—		118,509

Total assets	$	49,733	$	118,509	$	—	$	168,242

Liabilities:
Preferred stock warrant liability	$	—	$	—	$	6	$	6
Total liabilities	$	—	$	—		6	$	6

Schedule of Roll Forward of Fair Value of the Level 3 Preferred Stock Warrant Liability

The following table represents a roll-forward of the fair value of the Level 3 preferred stock warrant liability for each of the periods indicated (in thousands):


	As of December 31,
	2025			2024
Fair value, beginning of year	$	6		$	14
Change in estimated fair value		(3	)		(8	)

Fair value, end of year	$	3		$	6

Schedule of Cash and Cash Equivalents and Marketable Securities

The following tables summarizes the Company’s cash, cash equivalents and marketable securities as of June 30, 2026 and December 31, 2025 (in thousands):


	Fair Value Measurements at June 30, 2026
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Credit Losses		Total
Cash and cash equivalents	$	17,983	$	—	$	—		$	—	$	17,983
U.S. Treasuries		16,465	$	—		(3	)		—		16,462

Total cash, cash equivalents, and marketable securities	$	34,448	$	—	$	(3	)	$	—	$	34,445

As reported:
Cash and cash equivalents	$	17,983	$	—	$	—		$	—	$	17,983
Marketable securities		16,465	$	—		(3	)		—		16,462

	$	34,448	$	—	$	(3	)	$	—	$	34,445


	Fair Value Measurements at December 31, 2025
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Credit Losses		Total
Cash and cash equivalents	$	40,405	$	—	$	—	$	—	$	40,405
U.S. Treasuries		40,058		23		—		—		40,081

Total cash, cash equivalents, and marketable securities	$	80,463	$	23	$	—	$	—	$	80,486

As reported:
Cash and cash equivalents	$	40,405	$	—	$	—	$	—	$	40,405
Marketable securities		40,058		23		—		—		40,081

	$	80,463	$	23	$	—	$	—	$	80,486

The following tables summarizes the Company’s cash, cash equivalents and marketable securities as of December 31, 2025 and 2024 (in thousands):


	Fair Value Measurements at December 31, 2025
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Credit Losses		Total
Cash	$	500	$	—	$	—	$	—	$	500
Money market funds		39,905		—		—		—		39,905
U.S. Treasuries		40,058		23		—		—		40,081

Total cash, cash equivalents, and marketable securities	$	80,463	$	23	$	—	$	—	$	80,486

As reported:
Cash and cash equivalents	$	40,405	$	—	$	—	$	—	$	40,405
Marketable securities		40,058		23		—		—		40,081

	$	80,463	$	23	$	—	$	—	$	80,486


	Fair Value Measurements at December 31, 2024
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Credit Losses		Total
Cash	$	28	$	—	$	—		$	—	$	28
Money market funds		49,733		—		—			—		49,733
U.S. Treasuries		118,536		30		(57	)		—		118,509

Total cash, cash equivalents, and marketable securities	$	168,297	$	30	$	(57	)	$	—	$	168,270

As reported:
Cash and cash equivalents	$	49,761	$	—	$	—		$	—	$	49,761
Marketable securities		118,536		30		(57	)		—		118,509

	$	168,297	$	30	$	(57	)	$	—	$	168,270

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2025

Income Tax Disclosure [Abstract]

Summary of Company's Statutory Income Tax Rate to the Company's Effective Income Tax Rate

A reconciliation of the Company’s statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2025						2024
	Amount (in thousands)			Rate			Amount (in thousands)			Rate
Federal statutory income tax rate		(21,127	)		21.00	%		(17,523	)		21.00	%
Permanent difference		777			(0.77	)%		644			(0.77	)%
State taxes, net of federal benefit		73			(0.07	)%		(123	)		0.15	%
Research and development credits		(3,781	)		3.76	%		(4,999	)		5.99	%
Change in valuation allowance		24,058			(23.91	)%		22,002			(26.37	)%

Effective income tax rate		—			0.00	%		—			0.00	%

Summary of Net Deferred Tax Assets (Liabilities)

Net deferred tax assets (liabilities) as of December 31, 2025 and 2024 consisted of the following (in thousands):


	Year Ended December 31,
	2025			2024
Deferred tax assets
Net operating loss carryforwards	$	49,893		$	17,753
Research and development tax credit carryforwards		23,251			18,430
Lease right-of-use liability		1,794			1,800
Accrued expenses and other liabilities		885			1,352
Stock Compensation Expense		2,815			2,192
IRC 174 capitalized research and development		19,836			27,129
Other		1,202			662

Total deferred tax assets		99,676			69,319
Less: Valuation allowance		(98,055	)		(67,584	)

Net deferred tax assets		1,621			1,735

Deferred tax liabilities
Lease right-of-use asset		(1,728	)		(1,734	)
Depreciation		107			(1	)

Total deferred tax liabilities		(1,621	)		(1,735	)

Net deferred tax assets (liabilities)	$	—		$	—

Summary of Changes in the Valuation Allowance for Deferred Tax Assets

Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2025 and 2024 related primarily to the increase in net operating loss carryforwards and were as follows (in thousands):


	Year Ended December 31,
	2025		2024
Valuation allowance at the beginning of the year	$	67,584	$	40,458
Increases recorded to income tax provision		30,471		27,126

Valuation allowance at end of the year	$	98,055	$	67,584

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024
Accrued Liabilities and Other Liabilities [Abstract]
Compensation and benefits	$ 2,536	$ 3,830	$ 5,560
External research and development costs	7,722	6,361	3,959
Legal and professional fees	5,392	685	780
Other	2,203	1,415	979
Total accrued expenses and other current liabilities	$ 17,853	$ 12,291	$ 11,278

Summary of Significant Accounting Policies - Schedule of Property Plant and Equipment Estimated Useful Life (Details)	Dec. 31, 2025
Laboratory equipment [Member]
Property Plant And Equipment Estimated Useful Life [Line Items]
Property, plant, and equipment, useful life	5 years
Leasehold improvements [Member]
Property Plant And Equipment Estimated Useful Life [Line Items]
Leasehold improvements	0 years
Furniture and fixtures [Member]
Property Plant And Equipment Estimated Useful Life [Line Items]
Property, plant, and equipment, useful life	5 years
Computer software [Member]
Property Plant And Equipment Estimated Useful Life [Line Items]
Property, plant, and equipment, useful life	3 years

Financial Instruments and Fair Value Measurements - Additional Information (Details) - Series A Preferred Stock [Member] - $ / shares	May 25, 2028	Dec. 31, 2025	Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shares, issued	22,124
Shares issued, price per share	$ 1.1291
Class of warrant or right, exercise price of warrants or rights		$ 0.13	$ 0.28

Financial Instruments and Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Fair Value, Inputs, Level 3 [Member] \| Preferred stock warrant liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Liabilities		$ 3	$ 6	$ 14
Fair Value, Recurring [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	$ 34,195	79,986	168,242
Liabilities, Fair Value Disclosure [Abstract]
Liabilities	1	3	6
Fair Value, Recurring [Member] \| Money Market Funds [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	17,733	39,905	49,733
Fair Value, Recurring [Member] \| U.S. Treasuries [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	16,462	40,081	118,509
Fair Value, Recurring [Member] \| Preferred stock warrant liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Liabilities	1	3	6
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	17,733	39,905	49,733
Liabilities, Fair Value Disclosure [Abstract]
Liabilities	0	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Money Market Funds [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	17,733	39,905	49,733
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| U.S. Treasuries [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	0	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Preferred stock warrant liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Liabilities	0	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	16,462	40,081	118,509
Liabilities, Fair Value Disclosure [Abstract]
Liabilities	0	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Money Market Funds [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	0	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| U.S. Treasuries [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	16,462	40,081	118,509
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Preferred stock warrant liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Liabilities	0	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	0	0	0
Liabilities, Fair Value Disclosure [Abstract]
Liabilities	1	3	6
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Money Market Funds [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	0	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| U.S. Treasuries [Member]
Assets, Fair Value Disclosure [Abstract]
Assets	0	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Preferred stock warrant liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Liabilities	$ 1	$ 3	$ 6

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Property Plant And Equipment Estimated Useful Life [Line Items]
Impairment of long-lived assets to be disposed	$ 0	$ 0
Effective income tax rate reconciliation, percent	0.00%	0.00%
Maximum [Member]
Property Plant And Equipment Estimated Useful Life [Line Items]
Effective income tax rate reconciliation, percent	50.00%

Financial Instruments and Fair Value Measurements

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Fair Value Disclosures [Abstract]

Financial Instruments and Fair Value Measurements

3. Financial Instruments and Fair Value Measurements

Assets and Liabilities Measured at Fair Value on a Recurring Basis


	Fair Value Measurements at June 30, 2026
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	17,733	$	—	$	—	$	17,733
U.S. Treasuries		—		16,462		—	$	16,462

Total assets	$	17,733	$	16,462	$	—	$	34,195

Liabilities:
Preferred stock warrant liability	$	—	$	—	$	1	$	1

Total liabilities	$	—	$	—	$	1	$	1


	Fair Value Measurements at December 31, 2025
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	39,905	$	—	$	—	$	39,905
U.S. Treasuries		—		40,081		—		40,081

Total assets	$	39,905	$	40,081	$	—	$	79,986

Liabilities:
Preferred stock warrant liability	$	—	$	—	$	3	$	3

Total liabilities	$	—	$	—	$	3	$	3

There were no transfers between Level 1, Level 2 and Level 3 categories during the three and six months ended June 30, 2026.

Warrants to Purchase Redeemable Convertible Preferred Stock Subject to Conditional Redemption

There were no material changes to the terms, classification, or accounting for the Company’s warrants to purchase redeemable convertible preferred stock subject to conditional redemption during the three and six months ended June 30, 2026.

Cash and Cash Equivalents and Marketable Securities

The following tables summarizes the Company’s cash, cash equivalents and marketable securities as of June 30, 2026 and December 31, 2025 (in thousands):


	Fair Value Measurements at June 30, 2026
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Credit Losses		Total
Cash and cash equivalents	$	17,983	$	—	$	—		$	—	$	17,983
U.S. Treasuries		16,465	$	—		(3	)		—		16,462

Total cash, cash equivalents, and marketable securities	$	34,448	$	—	$	(3	)	$	—	$	34,445

As reported:
Cash and cash equivalents	$	17,983	$	—	$	—		$	—	$	17,983
Marketable securities		16,465	$	—		(3	)		—		16,462

	$	34,448	$	—	$	(3	)	$	—	$	34,445


	Fair Value Measurements at December 31, 2025
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Credit Losses		Total
Cash and cash equivalents	$	40,405	$	—	$	—	$	—	$	40,405
U.S. Treasuries		40,058		23		—		—		40,081

Total cash, cash equivalents, and marketable securities	$	80,463	$	23	$	—	$	—	$	80,486

As reported:
Cash and cash equivalents	$	40,405	$	—	$	—	$	—	$	40,405
Marketable securities		40,058		23		—		—		40,081

	$	80,463	$	23	$	—	$	—	$	80,486

None of the Company’s

available-for-sale

marketable securities had remaining maturities longer than one year as of June 30, 2026 and December 31, 2025.

As of June 30, 2026, the aggregate unrealized losses on the Company’s investment securities were immaterial. The Company has the intent and ability to hold such securities until recovery. As a result, the Company did not record any charges for credit-related impairments for its marketable debt securities for the three and six months ended June 30, 2026.

3. Financial Instruments and Fair Value Measurements

Assets and Liabilities Measured at Fair Value on a Recurring Basis


	Fair Value Measurements at December 31, 2025
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	39,905	$	—	$	—	$	39,905
U.S. Treasuries		—		40,081		—		40,081

Total assets	$	39,905	$	40,081	$	—	$	79,986

Liabilities:
Preferred stock warrant liability	$	—	$	—	$	3	$	3
Total liabilities	$	—	$	—	$	3	$	3


	Fair Value Measurements at December 31, 2024
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	49,733	$	—	$	—	$	49,733
U.S. Treasuries		—		118,509		—		118,509

Total assets	$	49,733	$	118,509	$	—	$	168,242

Liabilities:
Preferred stock warrant liability	$	—	$	—	$	6	$	6
Total liabilities	$	—	$	—		6	$	6

Warrants to Purchase Redeemable Convertible Preferred Stock Subject to Conditional Redemption

In connection with the PacificWestern Bank (“PWB”) term loan entered into May 2018, the Company granted PWB a warrant to purchase 22,124 shares of Series

A-1

preferred stock at an exercise price of $1.1291 per share. The warrant, which was deemed to be classified as a liability, expires on May 25, 2028. The term loan with PWB was fully paid in January 2019 and has since expired. As of December 31, 2025, the warrant has not been exercised.

The fair value of the preferred stock warrant liability is based on significant inputs not observable in the market, which represent a Level 3 measurement within the fair value hierarchy. The Company’s valuation of the preferred stock warrant utilized the Black-Scholes option-pricing model, which incorporates a number of assumptions and estimates. Changes in the fair value of the preferred stock warrant are recognized as other income (expense) in the consolidated statements of operations and comprehensive loss and were not material for the years ended December 31, 2025 and 2024.

As of December 31, 2025 and 2024, the estimated fair value of the Series

A-1

warrant was $0.13 and $0.28 per share, respectively. The fair value of each warrant share is estimated on the date of grant and at each reporting period using the Black-Scholes option pricing model, which requires inputs based on certain subjective assumptions including fair value of the underlying preferred stock, estimated volatility, expected term, risk-free interest rate, and expected dividend yield.

The Company assesses its financial liabilities measured at fair value on a recurring basis and transfers its financial liabilities between the relevant fair value hierarchies at the end of each reporting period, as needed. The following table represents a roll-forward of the fair value of the Level 3 preferred stock warrant liability for each of the periods indicated (in thousands):


	As of December 31,
	2025			2024
Fair value, beginning of year	$	6		$	14
Change in estimated fair value		(3	)		(8	)

Fair value, end of year	$	3		$	6

As of December 31, 2025 and 2024 there were no transfers between Level 1, Level 2 and Level 3.

Cash and Cash Equivalents and Marketable Securities

The following tables summarizes the Company’s cash, cash equivalents and marketable securities as of December 31, 2025 and 2024 (in thousands):


	Fair Value Measurements at December 31, 2025
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Credit Losses		Total
Cash	$	500	$	—	$	—	$	—	$	500
Money market funds		39,905		—		—		—		39,905
U.S. Treasuries		40,058		23		—		—		40,081

Total cash, cash equivalents, and marketable securities	$	80,463	$	23	$	—	$	—	$	80,486

As reported:
Cash and cash equivalents	$	40,405	$	—	$	—	$	—	$	40,405
Marketable securities		40,058		23		—		—		40,081

	$	80,463	$	23	$	—	$	—	$	80,486


	Fair Value Measurements at December 31, 2024
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Credit Losses		Total
Cash	$	28	$	—	$	—		$	—	$	28
Money market funds		49,733		—		—			—		49,733
U.S. Treasuries		118,536		30		(57	)		—		118,509

Total cash, cash equivalents, and marketable securities	$	168,297	$	30	$	(57	)	$	—	$	168,270

As reported:
Cash and cash equivalents	$	49,761	$	—	$	—		$	—	$	49,761
Marketable securities		118,536		30		(57	)		—		118,509

	$	168,297	$	30	$	(57	)	$	—	$	168,270

None of the Company’s

available-for-sale

marketable securities had remaining maturities longer than one year as of December 31, 2025 and 2024.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
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+ Details

Net Loss Per Share (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Earnings Per Share [Abstract]

Schedule of Company's Basic and Diluted Net Loss Per Share

The following table sets forth the computation of the Company basic and diluted net loss per share for the periods presented (in thousands, except share and per share amounts):


	Three Months Ended June 30,						Six Months Ended June 30,
	2026			2025			2026			2025
Numerator:
Net loss	$	(25,864	)	$	(26,896	)	$	(45,497	)	$	(51,882	)

Denominator
Weighted-average common shares outstanding, basic and diluted		21,808,064			13,939,366			19,751,933			13,931,419

Net loss per share attributable to common stockholders, basic and diluted	$	(1.19	)	$	(1.93	)	$	(2.30	)	$	(3.72	)

The following table sets forth the computation of the Company’s basic and diluted net loss per share for the periods presented (in thousands, except share and per share amounts):


	Year Ended December 31,
	2025			2024
Numerator:
Net loss	$	(100,607	)	$	(83,109	)

Denominator
Weighted-average common shares outstanding, basic and diluted		13,935,769			12,848,484

Net loss per share attributable to common stockholders, basic and diluted	$	(7.22	)	$	(6.47	)

Schedule of Diluted Net Loss Per Share Attributable to Common Stockholders

Obsidian Sub excluded the following shares from the computation of diluted net loss per share attributable to common stockholders during the three and six months ended June 30, 2026 and 2025 because including them would have had an anti-dilutive effect:


	For the Three and Six Months Ended June 30,
	2026	2025
Redeemable convertible preferred stock	207,952,902	215,038,192
Warrants to purchase Series A-1 redeemable convertible preferred stock	22,124	22,124
Options to purchase common stock	35,635,693	39,247,349

Total	243,610,719	254,307,665

The Company excluded the following shares from the computation of diluted net loss per share attributable to common stockholders’ during the year ended December 31, 2025, and 2024 because including them would have had an anti-dilutive effect:


	Year Ended December 31,
	2025		2024
Redeemable convertible preferred stock		215,038,192		215,038,192
Warrants to purchase Series A-1 redeemable convertible preferred stock		22,124		22,124
Options to purchase common stock		38,061,610		40,628,032

Total		253,121,926		255,688,348

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024
Property, Plant, and Equipment [Line Items]
Property, plant, and equipment		$ 11,421	$ 11,348
Less: accumulated depreciation		(9,510)	(8,026)
Property and equipment, net	$ 1,201	1,911	3,322
Laboratory equipment [Member]
Property, Plant, and Equipment [Line Items]
Property, plant, and equipment		10,017	9,944
Leasehold improvements [Member]
Property, Plant, and Equipment [Line Items]
Property, plant, and equipment		261	261
Furniture and fixtures [Member]
Property, Plant, and Equipment [Line Items]
Property, plant, and equipment		758	758
Computer software [Member]
Property, Plant, and Equipment [Line Items]
Property, plant, and equipment		$ 385	$ 385

- Definition

Amount of accumulated depreciation, depletion, and amortization of property, plant, and equipment. Includes, but is not limited to, land and land improvement; building; machinery and equipment; furniture and fixture; and work of art, historical treasure, or similar asset classified as collection.

+ References + Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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+ Details

- Definition

Amount, after accumulated depreciation, depletion, and amortization, of property, plant, and equipment. Includes, but is not limited to, land and land improvement; building; machinery and equipment; furniture and fixture; and work of art, historical treasure, or similar asset classified as collection.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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+ Details

Common Stock - Additional Information (Details) - shares	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024
Stockholders' Equity Note [Abstract]
Common stock, shares authorized	274,320,131	274,320,131	274,320,131
Preferred Stock, Shares Authorized	215,060,316	215,060,316	215,060,316
Preferred Stock, Shares Outstanding	207,952,902	215,038,192	215,038,192

- Definition

The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

+ References + Details

- Definition

Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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+ Details

Stock-Based Compensation (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Share-Based Payment Arrangement [Abstract]

Summary of the Fair Value of the Stock Options

The Company estimates the fair value of the stock options issued using the Black-Scholes option pricing model on the date of grant. The key assumptions used to apply this pricing model were as follows:


	June 30,
	2026			2025
Fair value of common stock	$	0.78-0.96		$	0.78 – 1.13
Risk-free interest rate		3.94	%		4.26	%
Expected dividend yield		—			—
Expected term (in years)		5.9			6.0
Expected volatility		82.71	%		106.25	%


	December 31,
	2025			2024
Fair value of common stock	$	0.78 – 1.13		$	1.01 – 1.13
Risk-free interest rate		3.94	%		4.25	%
Expected dividend yield		—			—
Expected term (in years)		6.1			6.1
Expected volatility		89.54	%		133.20	%

Summary of the Option Activity

The following table summarizes option activity under the 2016 Plan for the six months ended June 30, 2026:


	Number of Options			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2025		38,061,610		$	0.77		6.9	$	298
Options granted		5,353,691			0.79
Options exercised		(1,161,144	)		0.72
Options forfeited		(2,441,148	)		0.78
Options expired		(4,177,316	)		0.77

Outstanding at June 30, 2026		35,635,693		$	0.78		7.4	$	6,528

Vested and exercisable at June 30, 2026		21,465,199		$	0.77		6.7	$	4,045
Unvested at June 30, 2026		14,170,494		$	0.78		8.2	$	2,102

The following table summarizes option activity under the 2016 Plan for the year ended December 31, 2025:


	Number of Options			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2024		40,628,032		$	1.03		8.4	$	4,146
Options granted		432,000			0.78
Options exercised		(20,146	)		0.97
Options forfeited		(2,530,814	)		1.05
Options expired		(447,462	)		1.00

Outstanding at December 31, 2025		38,061,610		$	0.77		6.9	$	298

Vested and exercisable at December 31, 2025		23,056,967		$	0.77		6.1	$	298
Unvested at December 31, 2025		15,004,643		$	0.78		8.2	$	—

Summary of the Stock-Based Compensation Expense

The Company has recorded stock-based compensation expense as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
Research and development	$	688	$	1,168	$	1,368	$	1,993
General and administrative		864		1,593		1,638		2,878

	$1,552		$2,761		$3,006		$4,871

The Company has recorded stock-based compensation expense as follows (in thousands):


	December 31,
	2025		2024
Research and development	$	3,733	$	2,938
General and administrative		5,198		4,122

	$	8,931	$	7,060

Segment Information - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Segment Reporting [Line Items]
Cash, Cash Equivalents, and Short-Term Investments	$ 34,400		$ 34,400		$ 80,500	$ 168,300
Share-Based Payment Arrangement, Noncash Expense	1,552	$ 2,762	3,006	$ 4,871	8,931	7,060
Research and Development Expense [Member]
Segment Reporting [Line Items]
Share-Based Payment Arrangement, Noncash Expense	700	1,200	1,400	2,000	3,700	2,900
General and Administrative Expense [Member]
Segment Reporting [Line Items]
Share-Based Payment Arrangement, Noncash Expense	$ 800	$ 1,600	$ 1,600	$ 2,900	$ 5,200	$ 4,100

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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-Name Accounting Standards Codification
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-Paragraph 30
-Subparagraph (b)
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26B

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26A

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 24: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Fees Summary	Aug. 28, 2026 USD ($)
Fees Summary [Line Items]
Total Offering	$ 517,944,689.99
Previously Paid Amount	0.00
Total Fee Amount	71,528.17
Total Offset Amount	0.00
Net Fee	$ 71,528.17
Offering Table N/A
Offset Table N/A	N/A
Combined Prospectus Table N/A	N/A

Summary of Significant Accounting Policies (Table)

12 Months Ended

Dec. 31, 2025

Accounting Policies [Abstract]

Schedule of Property Plant and Equipment Estimated Useful Life


		Estimated Useful Life
Laboratory equipment		5 years
Leasehold improvements		Shorter of the lease term or estimated useful life
Furniture and fixtures		5 years
Computer software		3 years

Financial Instruments and Fair Value Measurements - Schedule of Cash and Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024
Cash And Cash equivalents And Marketable Securities [Line Items]
Amortized Cost	$ 34,448	$ 80,463	$ 168,297
Gross Unrealized Gains	0	23	30
Gross Unrealized Losses	(3)	0	(57)
Credit Losses	0	0	0
Total	34,445	80,486	168,270
Cash [Member]
Cash And Cash equivalents And Marketable Securities [Line Items]
Amortized Cost		500	28
Gross Unrealized Gains		0	0
Gross Unrealized Losses		0	0
Credit Losses		0	0
Total		500	28
Money market funds [Member]
Cash And Cash equivalents And Marketable Securities [Line Items]
Amortized Cost		39,905	49,733
Gross Unrealized Gains		0	0
Gross Unrealized Losses		0	0
Credit Losses		0	0
Total		39,905	49,733
U.S. Treasuries [Member]
Cash And Cash equivalents And Marketable Securities [Line Items]
Amortized Cost	16,465	40,058	118,536
Gross Unrealized Gains		23	30
Gross Unrealized Losses	(3)	0	(57)
Credit Losses	0	0	0
Total	16,462	40,081	118,509
Cash and cash equivalents [Member]
Cash And Cash equivalents And Marketable Securities [Line Items]
Amortized Cost	17,983	40,405	49,761
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Credit Losses	0	0	0
Total	17,983	40,405	49,761
Marketable securities [Member]
Cash And Cash equivalents And Marketable Securities [Line Items]
Amortized Cost	16,465	40,058	118,536
Gross Unrealized Gains		23	30
Gross Unrealized Losses	(3)	0	(57)
Credit Losses	0	0	0
Total	$ 16,462	$ 40,081	$ 118,509

Submission	Aug. 28, 2026
Submission [Line Items]
Central Index Key	0002130606
Registrant Name	Obsidian Therapeutics, Inc.
Form Type	S-1
Submission Type	S-1
Fee Exhibit Type	EX-FILING FEES

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized	48,749,161		48,749,161	48,749,161
Common stock, capital shares reserved for future issuance	5,330,455		4,475,263	1,993,987
Share based compensation weighted average fair value of options granted	$ 0.57	$ 0.72	$ 0.62	$ 1.03
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period	2,441,148		2,530,814
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross	5,353,691		432,000		1,231,034
Unrecognized compensation expense	$ 11.2		$ 13.3
Unrecognized Compensation Expense Relating To The PerformanceBased Awards	1.0
Stock issued during period, value, stock options exercised	$ 0.3	$ 0.1	$ 0.0	$ 0.8
Share based compensation expenses weighted average period	2 years 1 month 6 days		2 years 10 days
Share-based compensation arrangement by share-based payment award, options, outstanding, number	35,635,693		38,061,610	40,628,032
Performance Shares [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period	354,074
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross	1,883,750
Share-based compensation arrangement by share-based payment award, options, outstanding, number			2,027,700
Share-based payment arrangement, expense			$ 0.2	$ 0.7
Performance Shares [Member] \| 2023 [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross					442,592
Performance Shares [Member] \| 2024 [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross				354,074

Commitments and Contingencies	6 Months Ended	12 Months Ended
Commitments and Contingencies	Jun. 30, 2026	Dec. 31, 2025
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies 401(k) Plan In January 2017, and as amended in February 2020, the Company established a defined contribution plan under Section 401(k) of the Internal Revenue Code (the “401(k) Plan”). The 401(k) Plan covers all employees who meet defined minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. Starting in 2020, the Company makes matching contributions at a rate of 100% of each employee’s contribution up to a maximum employee contribution of 3% of eligible plan compensation. The Company made matching contributions of $0.1 million and $0.3 million for each of the three and six months ended June 30, 2026 and 2025, respectively. Other Contractual Obligations The Company enters into contracts in the normal course of business with third parties for preclinical research studies, upcoming clinical trials and testing and manufacturing services. These contracts typically do not contain minimum purchase commitments and are generally cancelable by the Company upon written notice. Payments due upon cancellation consist of payments for services provided or expenses incurred, including noncancelable obligations of the service providers, up to the date of cancellation and in the case of certain arrangements may include noncancelable fees. Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, contract research organizations, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The Company has not incurred any material costs as a result of such indemnifications and is not currently aware of any indemnification claims. Legal Proceedings The Company is not a party to any material legal proceedings. At each reporting date, the Company evaluates whether a potential loss amount or a potential range of losses is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as incurred the costs related to such legal proceedings. Collaboration and License Agreement with University of Texas M.D. Anderson Cancer Center In November 2020, The Company entered into a multi-year collaborative research and option agreement (the “Collaboration Agreement”) with the Board of Regents (the “Board of Regents”) of The University of Texas System, on behalf of the University of Texas M.D. Anderson Cancer Center (“M.D. Anderson”), designed to expedite the research and development of novel engineered TIL for the treatment of solid tumors. Pursuant to the Collaboration Agreement, as amended, the Company agreed to fund research activities of up to $8.3 million over approximately two years and received the option to obtain a license to certain intellectual property arising from the collaboration. The collaboration focused on developing TIL containing regulated membrane-bound IL15 (“mbIL15”), with the potential to enhance anti-tumor efficacy and reduce tumor burden in patients suffering from different types of solid tumors. The collaboration’s purpose was to accelerate the development of cytoTIL ™ , including process and analytical development and clinical readiness activities. The Collaboration Agreement expired in 2023 and, prior to such expiration, the Company exercised its option to license certain intellectual property arising from the collaboration and subsequently entered into the resulting license agreement with the Board of Regents on behalf of M.D. Anderson (the (“M.D. Anderson License Agreement”) in October 2021. Under the M.D. Anderson License Agreement, the Company is obligated to pay to M.D. Anderson (a) a royalty on net sales of Developed Products and licensed products at a low single digit percentage (b) milestone payments of up to (i) $75.0 million upon the achievement of certain specified clinical and regulatory milestones and (ii) $90.0 million upon the achievement of certain specified sales milestones, which milestones may be payable with respect to multiple products and indications and (c) a share of certain consideration received by the Company from sublicensees under any sublicense agreements with third parties. As of June 30, 2026, no additional milestone payments were considered probable of achievement and, accordingly, no related liability has been recognized. The M.D. Anderson License Agreement may be terminated by the Board of Regents upon notice for an uncured challenge of the Board of Regents’ patents and by mutual agreement of us and the Board of Regents.	10. Commitments and Contingencies 401(k) Plan In January 2017, and as amended in February 2020, the Company established a defined contribution plan under Section 401(k) of the Internal Revenue Code (the “401(k) Plan”). The 401(k) Plan covers all employees who meet defined minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. Starting in 2020, the Company makes matching contributions at a rate of 100% of each employee’s contribution up to a maximum employee contribution of 3% of eligible plan compensation. For each of the years ended December 31, 2025 and 2024, the Company made matching contributions of $0.5 million. Other Contractual Obligations The Company enters into contracts in the normal course of business with third parties for preclinical research studies, upcoming clinical trials and testing and manufacturing services. These contracts typically do not contain minimum purchase commitments and are generally cancelable by the Company upon written notice. Payments due upon cancellation consist of payments for services provided or expenses incurred, including noncancelable obligations of the service providers, up to the date of cancellation and in the case of certain arrangements may include noncancelable fees. Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, contract research organizations, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The Company has not incurred any material costs as a result of such indemnifications and is not currently aware of any indemnification claims. Legal Proceedings The Company is not a party to any material legal proceedings. At each reporting date, the Company evaluates whether a potential loss amount or a potential range of losses is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as incurred the costs related to such legal proceedings. Collaboration and License Agreement with University of Texas M.D. Anderson Cancer Center In November 2020, the Company entered into a multi-year collaborative research and option agreement (the “Collaboration Agreement”) with the Board of Regents (the “Board of Regents”) of The University of Texas System, on behalf of the University of Texas M.D. Anderson Cancer Center (“M.D. Anderson”) designed to expedite the research and development of novel engineered TIL for the treatment of solid tumors. Pursuant to the Collaboration Agreement, as amended, the Company agreed to fund research activities of up to $8.3 million over approximately two years and received the option to obtain a license to certain intellectual property arising from the collaboration. The collaboration focused on developing TIL containing regulated membrane-bound IL15 (“mbIL15”) with the potential to enhance anti-tumor efficacy and reduce tumor burden in patients suffering from different types of solid tumors. The collaboration’s purpose was to accelerate the development of cytoTIL, including process and analytical development and clinical readiness activities. The Collaboration Agreement expired in 2023 and, prior to such expiration, the Company exercised its option to license certain intellectual property arising from the collaboration and subsequently entered into the resulting license agreement with the Board of Regents on behalf of M.D. Anderson (“M.D. Anderson License Agreement”) in October 2021. Under the M.D. Anderson License Agreement, the Company is obligated to pay to M.D. Anderson (a) a royalty on net sales of Developed Products and licensed products at a low single digit percentage (b) milestone payments of up to (i) $75.0 million upon the achievement of certain specified clinical and regulatory milestones and (ii) $90.0 million upon the achievement of certain specified sales milestones, which milestones may be payable with respect to multiple products and indications and (c) a share of certain consideration received by the Company from sublicensees under any sublicense agreements with third parties. As of December 31, 2025, no additional milestone payments were considered probable of achievement and, accordingly, no related liability has been recognized. The M.D. Anderson License Agreement may be terminated by the Board of Regents upon notice for an uncured challenge of the Board of Regents’ patents and by mutual agreement of us and the Board of Regents.

Redeemable Convertible Preferred Stock - Summary of Preferred Stock Is Summarized (Details) - USD ($)	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024
Preferred Stock Summarized [Line Items]
Total Shares Authorized	215,060,316	215,060,316	215,060,316
Total Shares Issued and Outstanding	207,952,902	215,038,192	215,038,192
Carrying Value	$ 330,028,000	$ 338,028,000	$ 338,028,000
Liquidation Preference	$ 329,001,000	$ 337,001,000	$ 337,001,000
Common Shares Issuable Upon Conversion	207,952,902	215,038,192	215,038,192
Series A1 Preferred Stock [Member]
Preferred Stock Summarized [Line Items]
Total Shares Authorized	33,222,339	33,222,339	33,222,339
Total Shares Issued and Outstanding	26,114,925	33,200,215	33,200,215
Carrying Value	$ 29,486,000	$ 37,486,000	$ 37,486,000
Liquidation Preference	$ 29,486,000	$ 37,486,000	$ 37,486,000
Common Shares Issuable Upon Conversion	26,114,925	33,200,215	33,200,215
Series A2 Preferred Stock [Member]
Preferred Stock Summarized [Line Items]
Total Shares Authorized	14,936,323	14,936,323	14,936,323
Total Shares Issued and Outstanding	14,936,323	14,936,323	14,936,323
Carrying Value	$ 16,807,000	$ 16,807,000	$ 16,807,000
Liquidation Preference	$ 14,936,000	$ 14,936,000	$ 14,936,000
Common Shares Issuable Upon Conversion	14,936,323	14,936,323	14,936,323
Series A3 Preferred Stock [Member]
Preferred Stock Summarized [Line Items]
Total Shares Authorized	6,146,592	6,146,592	6,146,592
Total Shares Issued and Outstanding	6,146,592	6,146,592	6,146,592
Carrying Value	$ 9,035,000	$ 9,035,000	$ 9,035,000
Liquidation Preference	$ 9,035,000	$ 9,035,000	$ 9,035,000
Common Shares Issuable Upon Conversion	6,146,592	6,146,592	6,146,592
Series B Preferred Stock [Member]
Preferred Stock Summarized [Line Items]
Total Shares Authorized	76,187,917	76,187,917	76,187,917
Total Shares Issued and Outstanding	76,187,917	76,187,917	76,187,917
Carrying Value	$ 114,732,000	$ 114,732,000	$ 114,732,000
Liquidation Preference	$ 115,044,000	$ 115,044,000	$ 115,044,000
Common Shares Issuable Upon Conversion	76,187,917	76,187,917	76,187,917
Series C Preferred Stock [Member]
Preferred Stock Summarized [Line Items]
Total Shares Authorized	84,567,145	84,567,145	84,567,145
Total Shares Issued and Outstanding	84,567,145	84,567,145	84,567,145
Carrying Value	$ 159,968,000	$ 159,968,000	$ 159,968,000
Liquidation Preference	$ 160,500,000	$ 160,500,000	$ 160,500,000
Common Shares Issuable Upon Conversion	84,567,145	84,567,145	84,567,145

Net Loss Per Share - Schedule of Company's Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2026	Mar. 31, 2026	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Earnings Per Share [Abstract]
Net Income (Loss) Attributable to Parent	$ (25,864)	$ (19,633)	$ (26,896)	$ (24,986)	$ (45,497)	$ (51,882)	$ (100,607)	$ (83,109)
Weighted Average Number of Shares Outstanding, Basic	21,808,064		13,939,366		19,751,933	13,931,419	13,935,769	12,848,484
Weighted Average Number of Shares Outstanding, Diluted	21,808,064		13,939,366		19,751,933	13,931,419	13,935,769	12,848,484
Earnings Per Share, Basic	$ (1.19)		$ (1.93)		$ (2.3)	$ (3.72)	$ (7.22)	$ (6.47)
Earnings Per Share, Diluted	$ (1.19)		$ (1.93)		$ (2.3)	$ (3.72)	$ (7.22)	$ (6.47)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482662/260-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 4
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482705/350-40-65-4

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (e)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479719/606-10-65-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
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-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
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-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 9
-Subparagraph (e)
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-URI https://asc.fasb.org/1943274/2147479343/105-10-65-9

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 17
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480336/718-10-65-17

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Topic 260
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-Name Accounting Standards Codification
-Section 55
-Paragraph 52
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-52

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
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-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
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-Name Accounting Standards Codification
-Section 50
-Paragraph 3
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-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 41: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 42: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479105/946-220-45-7

Reference 43: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 44: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 45: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(1)(d))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3

Reference 46: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 47: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 48: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 49: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 50: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1A

Reference 51: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
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-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1B

Reference 52: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Section 65
-Paragraph 4
-Subparagraph (f)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481538/470-20-65-4

Reference 53: http://fasb.org/us-gaap/role/ref/legacyRef
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-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

+ Details

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Income Taxes [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	$ 186,500	$ 66,200
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	171,000	61,200
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	17,100	13,300
Deferred Tax Assets, Tax Credit Carryforwards, Research	7,700	6,500
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 30,471	27,126
Percentage Of Tax Settlement With Taxing Authority	50.00%
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$ 0	$ 0
Valuation Allowance Deferred Tax Assets [Member]
Income Taxes [Line Items]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 30,500

Lease - Summary of Maturities of Operating Lease Liabilities (Details) $ in Thousands	Dec. 31, 2025 USD ($)
Lease, Cost [Abstract]
2026	$ 2,976
2027	855
2028	673
Total minimum lease payments	4,504
Less: Interest portion	(232)
Total present value of operating lease liabilities	$ 4,272

Income Taxes - Summary of Net Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Deferred tax assets
Net operating loss carryforwards	$ 49,893	$ 17,753
Research and development tax credit carryforwards	23,251	18,430
Lease right-of-use liability	1,794	1,800
Accrued expenses and other liabilities	885	1,352
Stock Compensation Expense	2,815	2,192
IRC 174 capitalized research and development	19,836	27,129
Other	1,202	662
Total deferred tax assets	99,676	69,319
Less: Valuation allowance	(98,055)	(67,584)	$ (40,458)
Net deferred tax assets	1,621	1,735
Deferred tax liabilities
Lease right-of-use asset	(1,728)	(1,734)
Depreciation	107	(1)
Total deferred tax liabilities	(1,621)	(1,735)
Net deferred tax assets (liabilities)	$ 0	$ 0

Income Taxes

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Income Tax Disclosure [Abstract]

Income Taxes

8. Income Taxes

No income tax expense was recorded during the three and six months ended June 30, 2026 or 2025. The Company maintained a full valuation allowance through June 30, 2026 due to uncertainty regarding its ability to utilize deferred tax assets.

9. Income Taxes

For the years ended December 31, 2025 and 2024, no income tax expense was recorded due to the Company’s net operating loss (“NOL”) and full valuation allowance. The Company has historically incurred net operating losses and maintains a full valuation allowance against its deferred tax assets.

All of the Company’s operating losses since inception have been generated in the United States.

The reported amount of income tax expense for the years differs from the amount that would result from applying domestic federal statutory rates to pretax losses primarily because of changes in the valuation allowance.

A reconciliation of the Company’s statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2025						2024
	Amount (in thousands)			Rate			Amount (in thousands)			Rate
Federal statutory income tax rate		(21,127	)		21.00	%		(17,523	)		21.00	%
Permanent difference		777			(0.77	)%		644			(0.77	)%
State taxes, net of federal benefit		73			(0.07	)%		(123	)		0.15	%
Research and development credits		(3,781	)		3.76	%		(4,999	)		5.99	%
Change in valuation allowance		24,058			(23.91	)%		22,002			(26.37	)%

Effective income tax rate		—			0.00	%		—			0.00	%

In 2025 and 2024, state and local income taxes in Massachusetts comprised the majority of the state and local income taxes, net of federal benefit category.

Net deferred tax assets (liabilities) as of December 31, 2025 and 2024 consisted of the following (in thousands):


	Year Ended December 31,
	2025			2024
Deferred tax assets
Net operating loss carryforwards	$	49,893		$	17,753
Research and development tax credit carryforwards		23,251			18,430
Lease right-of-use liability		1,794			1,800
Accrued expenses and other liabilities		885			1,352
Stock Compensation Expense		2,815			2,192
IRC 174 capitalized research and development		19,836			27,129
Other		1,202			662

Total deferred tax assets		99,676			69,319
Less: Valuation allowance		(98,055	)		(67,584	)

Net deferred tax assets		1,621			1,735

Deferred tax liabilities
Lease right-of-use asset		(1,728	)		(1,734	)
Depreciation		107			(1	)

Total deferred tax liabilities		(1,621	)		(1,735	)

Net deferred tax assets (liabilities)	$	—		$	—

As of December 31, 2025 and 2024, the Company had federal NOL carryforwards of $186.5 million and $66.2 million, respectively, and state NOL carryforwards of $171.0 million and $61.2 million, respectively, which may be available to offset future taxable income. Federal NOL carryforwards do not expire and state NOLs begin to expire in 2037.

As of December 31, 2025 and 2024, the Company also had federal research and development tax credit carryforwards of $17.1 million and $13.3 million, respectively, and state research and development credit carryforwards of $7.7 million and $6.5 million, respectively, which may be available to offset future income tax liabilities. Federal and state research and development tax credit carryforwards begin to expire in 2037 and 2031, respectively.

Utilization of the net operating loss carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 due to ownership change limitations that have occurred previously or that could occur in the future. These ownership changes may limit the amount of net operating loss carryforwards that can be utilized annually to offset future taxable income and tax, respectively. The Company has completed an evaluation of ownership changes through December 31, 2022 to assess whether utilization of the Company’s net operating loss or research and development credit carryforwards would be subject to an annual limitation under Section 382, and it was determined that an ownership change has occurred. The Company has determined that no attributes will expire unused, as of December 31, 2022, based on the limitation analysis. To the extent a subsequent ownership change occurs, the net operating loss and credit carryforwards may be subject to additional limitation.

The Company has not yet conducted a study of its research and development credit carryforwards. This study may result in an increase or decrease to the Company’s credit carryforwards, however, until a study is completed, and any adjustment is known, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company’s credits, and if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. As a result, there would be no impact to the consolidated statements of operations and comprehensive loss or consolidated statements of cash flows if an adjustment were required.

The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets, which are comprised principally of net operating loss carryforwards and research and development credit carryforwards. Management has considered the Company’s history of net losses incurred since inception and its lack of commercialization of any products or generation of revenue from product sales since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the deferred tax assets as of December 31, 2025 and 2024. Management reevaluates the positive and negative evidence at each reporting period.


	Year Ended December 31,
	2025		2024
Valuation allowance at the beginning of the year	$	67,584	$	40,458
Increases recorded to income tax provision		30,471		27,126

Valuation allowance at end of the year	$	98,055	$	67,584

The increase in the valuation allowance of $30.5 million during the year ended December 31, 2025 related primarily to the increase in net operating loss carryforwards.

The Company assesses the uncertainty in its income tax positions to determine whether a tax position of the Company is more likely than not to be sustained upon examination, including resolution of any related appeals of litigation processes, based on the technical merits of the position. For the tax position meeting the

more-likely-than-not

threshold, the tax amount recognized in the financial statements is reduced by the largest benefit that has a greater than 50% likelihood of being realized upon the ultimate settlement with the relevant taxing authority. As of December 31, 2025 and 2024, the Company had

not

recorded any reserves for uncertain tax positions or related interest and penalties.

The Company files income tax returns as prescribed by the tax law of the jurisdiction in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdiction, where applicable. Since the Company is in a loss carryforward position, it is generally subject to examination by the U.S. federal, state, and local income tax authorities for all tax years in which a loss carryforward is available.

- Definition

The entire disclosure for income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477617/942-740-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478822/944-740-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 5: http://www.xbrl.org/2003/role/exampleRef
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-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 231
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12C

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12B

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477891/740-270-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-13

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/740/tableOfContent

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-14

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-21

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-17

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482603/740-30-50-2

+ Details

Cover	6 Months Ended
Cover	Jun. 30, 2026
Document Information [Line Items]
Document Type	S-1
Amendment Flag	false
Entity Central Index Key	0002130606
Entity Registrant Name	OBSIDIAN THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Primary SIC Number	2834
Entity Tax Identification Number	42-1977778
Entity Address, Address Line One	1030 Massachusetts Avenue
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02138
City Area Code	781
Local Phone Number	806-6245
Entity Small Business	false
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Business Contact [Member]
Document Information [Line Items]
Contact Personnel Name	Madan Jagasia
Entity Address, Address Line One	1030 Massachusetts Avenue
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02138
City Area Code	781
Local Phone Number	806-6245

Stock-Based Compensation - Summary of the Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Share Based Compensation Expenses [Line Items]
Employee Benefits and Share-Based Compensation	$ 1,552	$ 2,761	$ 3,006	$ 4,871	$ 8,931	$ 7,060
Research Development Expense [Member]
Share Based Compensation Expenses [Line Items]
Employee Benefits and Share-Based Compensation	688	1,168	1,368	1,993	3,733	2,938
General Administrative Expense [Member]
Share Based Compensation Expenses [Line Items]
Employee Benefits and Share-Based Compensation	$ 864	$ 1,593	$ 1,638	$ 2,878	$ 5,198	$ 4,122

Net Loss Per Share

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Earnings Per Share [Abstract]

Net Loss Per Share

11. Net Loss Per Share

The following table sets forth the computation of the Company basic and diluted net loss per share for the periods presented (in thousands, except share and per share amounts):


	Three Months Ended June 30,						Six Months Ended June 30,
	2026			2025			2026			2025
Numerator:
Net loss	$	(25,864	)	$	(26,896	)	$	(45,497	)	$	(51,882	)

Denominator
Weighted-average common shares outstanding, basic and diluted		21,808,064			13,939,366			19,751,933			13,931,419

Net loss per share attributable to common stockholders, basic and diluted	$	(1.19	)	$	(1.93	)	$	(2.30	)	$	(3.72	)


	For the Three and Six Months Ended June 30,
	2026	2025
Redeemable convertible preferred stock	207,952,902	215,038,192
Warrants to purchase Series A-1 redeemable convertible preferred stock	22,124	22,124
Options to purchase common stock	35,635,693	39,247,349

Total	243,610,719	254,307,665

12. Net Loss Per Share

The following table sets forth the computation of the Company’s basic and diluted net loss per share for the periods presented (in thousands, except share and per share amounts):


	Year Ended December 31,
	2025			2024
Numerator:
Net loss	$	(100,607	)	$	(83,109	)

Denominator
Weighted-average common shares outstanding, basic and diluted		13,935,769			12,848,484

Net loss per share attributable to common stockholders, basic and diluted	$	(7.22	)	$	(6.47	)


	Year Ended December 31,
	2025		2024
Redeemable convertible preferred stock		215,038,192		215,038,192
Warrants to purchase Series A-1 redeemable convertible preferred stock		22,124		22,124
Options to purchase common stock		38,061,610		40,628,032

Total		253,121,926		255,688,348

Income Taxes - Summary of Company's Statutory Income Tax Rate to the Company's Effective Income Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Amount (in thousands)
Federal statutory income tax rate, Amount					$ (21,127)	$ (17,523)
Permanent difference, Amount					777	644
State taxes, net of federal benefit, Amount					73	(123)
Research and development credits, Amount					(3,781)	(4,999)
Change in valuation allowance, Amount					24,058	22,002
Effective income tax rate, Amount	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Rate
Federal statutory income tax rate, Rate					21.00%	21.00%
Permanent difference, Rate					(0.77%)	(0.77%)
State taxes, net of federal benefit, Rate					(0.07%)	0.15%
Research and development credits, Rate					3.76%	5.99%
Change in valuation allowance, Rate					(23.91%)	(26.37%)
Effective income tax rate, Rate					0.00%	0.00%

Summary of Significant Accounting Policies (Policies)

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Accounting Policies [Abstract]

Basis of Presentation

There were no changes to the Company’s significant accounting policies during the six months ended June 30, 2026, other than noted below.

Basis of Presentation

Use of Estimates

Cash and Cash Equivalents

Marketable Securities

non-credit-related

unrealized losses recorded in other comprehensive income (loss). The Company did not recognize any credit loss relating to its investments for the years ended December 31, 2025 or 2024.

Segment Information

Concentration of Credit Risk and of Significant Suppliers

off-balance

sheet concentrations of credit risk such as foreign exchange contracts, option contracts or other foreign hedging arrangements.

Restricted Cash

Property and Equipment


		Estimated Useful Life
Laboratory equipment		5 years
Leasehold improvements		Shorter of the lease term or estimated useful life
Furniture and fixtures		5 years
Computer software		3 years

Impairment of Long-Lived Assets

Leases

In accordance with ASU

2016-02,

Leases

The Company enters into contracts that contain both lease and

non-lease

components.

Non-lease

components may include maintenance, utilities, and other operating costs. For leases of real estate, the Company combines the lease and associated

non-lease

components in its lease arrangements as a single lease component. Variable costs, such as utilities or maintenance costs, are not included in the measurement of

right-of-use

assets and lease liabilities, but rather are expensed when the event determining the amount of variable consideration to be paid occurs.

Level 1

- Quoted prices in active markets for identical assets or liabilities.

Level 2

Level 3

Redeemable Convertible Preferred Stock

Collaboration Agreements

The Company analyzes its collaboration arrangements to assess whether they are within the scope of ASC 808,

Collaborative Arrangements

Revenue from Contracts with Customers

(“ASC 606”).

Revenue Recognition

re-evaluates

the estimate of variable consideration and the constraint.

Research and Development and Manufacturing Contract Costs and Accruals

Patent Costs

Stock-Based Compensation

The fair value of each share option is estimated on the date of grant using the Black-Scholes option pricing model, which requires inputs based on certain subjective assumptions, including:

•

Fair Value of Common Stock

•

Estimated Volatility

•

Expected Term

time-to-vesting

•

Risk Free Interest Rate

•

Dividend Yield

—The Company has used an expected dividend yield of zero based on the fact that it has never paid cash dividends on its ordinary shares and does not expect to pay any cash dividends in the future.

Income Taxes

The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a

two-step

more-likely-than-not

Net Loss Per Share

The Company calculated basic and diluted net loss per share attributable to common stockholders in conformity with the

two-class

method required for companies with participating securities. The Company’s

two-class

method determines net loss per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The

two-class

method during periods of loss since the participating securities do not have a contractual obligation to share in the losses of the Company.

Under the

two-class

Other Comprehensive Loss

Recently Adopted Accounting Pronouncements

In December 2023, the FASB issued ASU

No. 2023-09,

Income Taxes (Topic 740): Improvement to Income Tax Disclosures

(“ASU

2023-09”),

to enhance the transparency and decision usefulness of income tax disclosures. ASU

2023-09

did not result in a material impact to the consolidated financial statements and related disclosures.

Deferred Offering Costs

paid-in

capital, as applicable, upon closing of the merger transaction and Concurrent PIPE Financing.

Recently Issued Accounting Standards Not Yet Adopted

In November 2024, the FASB issued ASU

2024-03,

Income Statement–Reporting Comprehensive Income–Expense Disaggregation Disclosures (Subtopic

220-40):

Disaggregation of Income Statement Expenses

, or ASU

2024-03

which requires public business entities to disclose specified information about certain costs and expenses on an interim and annual basis. ASU

2024-03

will have on its consolidated financial statements and related disclosures.

In December 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”)

No. 2025-12,

2025-12

on its consolidated financial statements and related disclosures.

Recently Issued Accounting Standards Not Yet Adopted

In November 2024, the FASB issued ASU

2024-03,

Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic

220-40):

Disaggregation of Income Statement Expenses

(“ASU

2024-03”)

2024-03

will have on our financial statement disclosures.

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Property, Plant, and Equipment [Abstract]
Depreciation expense	$ 1.5	$ 1.5

Redeemable Convertible Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2025	Dec. 31, 2024	Feb. 28, 2026
Redeemable Convertible Preferred Stock [Line Items]
Preferred Stock, Par or Stated Value Per Share		$ 0.0001
Proceeds from Issuance of Preferred Stock and Preference Stock		$ 0	$ 160,500
Payments of Stock Issuance Costs		$ 0	$ 532
Preferred Stock, Convertible, Conversion Price				$ 1.1291
Stock Exchange Share Price		$ 2.8469
Convertible Preferred Stock, Shares Issued upon Conversion				7,085,290
Preferred Stock [Member]
Redeemable Convertible Preferred Stock [Line Items]
Sale of Stock, Price Per Share		$ 2.8469
Proceeds from Issuance Initial Public Offering		$ 100,000
Series A1 Preferred Stock [Member]
Redeemable Convertible Preferred Stock [Line Items]
Preferred Stock, Par or Stated Value Per Share				$ 0.0001
Shares Issued, Price Per Share		$ 1.1291
Preferred Stock, Convertible, Conversion Price		1.1291
Series A2 Preferred Stock [Member]
Redeemable Convertible Preferred Stock [Line Items]
Shares Issued, Price Per Share		1
Preferred Stock, Convertible, Conversion Price		1
Series A3 Preferred Stock [Member]
Redeemable Convertible Preferred Stock [Line Items]
Shares Issued, Price Per Share		1.47
Preferred Stock, Convertible, Conversion Price		1.47
Series B Preferred Stock [Member]
Redeemable Convertible Preferred Stock [Line Items]
Shares Issued, Price Per Share		1.51
Preferred Stock, Convertible, Conversion Price		1.51
Series C Preferred Stock [Member]
Redeemable Convertible Preferred Stock [Line Items]
Sale of Stock, Number of Shares Issued in Transaction	84,567,145
Sale of Stock, Price Per Share	$ 1.8979
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 160,500
Payments of Stock Issuance Costs	$ 500
Shares Issued, Price Per Share		1.8979
Preferred Stock, Convertible, Conversion Price		$ 1.8979

Related Party Transactions	6 Months Ended	12 Months Ended
Related Party Transactions	Jun. 30, 2026	Dec. 31, 2025
Related Party Transactions [Abstract]
Related Party Transactions	12. Related Party Transactions The Company entered into individual collaboration and license agreements with Celgene Corporation (“Celgene”) in 2019 and 2020, respectively, and a collaboration agreement with Vertex Pharmaceuticals, Inc., (“Vertex”) in 2021. Both Celgene and Vertex purchased the Company’s Preferred Stock in connection with the collaboration agreements. All performance obligations under the collaboration agreements were satisfied in previous reporting periods. Accordingly, during the three and six months ended June 30, 2026, the Company did not recognize related party revenue associated with the collaboration agreements. The Celgene collaboration agreement was terminated in October 2025 and the Celgene license agreement was terminated in November 2025. The Vertex collaboration agreement expired in April 2025. No future revenue associated with these collaboration arrangements will be recognized.	13. Related Party Transactions The Company entered into individual collaboration and license agreements with Celgene Corporation (“Celgene”) in 2019 and 2020, respectively, and a collaboration agreement with Vertex Pharmaceuticals, Inc. (“Vertex”) in 2021. Both Celgene and Vertex purchased the Company’s Preferred Stock in connection with the collaboration agreements. All performance obligations under the collaboration agreements were satisfied in previous reporting periods. Accordingly, during the years ended December 31, 2025 and 2024, the Company did not recognize related party revenue associated with the collaboration agreements. The Celgene collaboration agreement was terminated in October 2025 and the Celgene license agreement was terminated in November 2025. The Vertex collaboration agreement expired in April 2025. No future revenue associated with these collaboration arrangements will be recognized.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477657/942-210-S45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478478/942-210-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7)(e)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-5

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-6

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/850/tableOfContent

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-6

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

+ Details

Leases (Tables)

12 Months Ended

Dec. 31, 2025

Lease, Cost [Abstract]

Lease, Cost [Table Text Block]

During the year ended December 31, 2025, and 2024, the components of operating lease cost were as follows, and are reflected in general and administrative expenses and research and development expenses, as determined by the underlying activities (in thousands):


	December 31,
	2025		2024
Lease cost
Operating lease cost	$	2,757	$	2,757
Variable operating lease cost		541		516

Total operating lease cost	$	3,298	$	3,273

Schedule Of Operating Leases [Text Block]

The following table summarizes information related to the measurement of the Company’s operating leases for the years ended December 31, 2025 and 2024 (in thousands):


	December 31,
	2025			2024
Weighted-average remaining lease term (years)		1.90			2.80
Weighted-average discount rate		6.82	%		7.13	%
Cash paid for amounts included in the measurement of operating lease liabilities	$	2,896		$	2,776

Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block]

Maturities of the Company’s operating lease liabilities at December 31, 2025 are as follows (in thousands):


2026	$	2,976
2027		855
2028		673

Total minimum lease payments		4,504
Less: Interest portion		(232	)

Total present value of operating lease liabilities	$	4,272

Accrued Expenses and Other Current Liabilities

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Accrued Liabilities and Other Liabilities [Abstract]

Accrued Expenses and Other Current Liabilities

4. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following (in thousands):


	June 30, 2026		December 31, 2025
Compensation and benefits	$	2,536	$	3,830
External research and development costs		7,722		6,361
Legal and professional fees		5,392		685
Other		2,203		1,415

Total accrued expenses and other current liabilities	$	17,853	$	12,291

5. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following (in thousands):


	December 31,
	2025		2024
Compensation and benefits	$	3,830	$	5,560
External research and development costs		6,361		3,959
Legal and professional fees		685		780
Other		1,415		979

Total accrued expenses and other current liabilities	$	12,291	$	11,278

Offerings - Offering: 1	Aug. 28, 2026 USD ($) shares
Offering:
Fee Previously Paid	false
Other Rule	true
Security Type	Equity
Security Class Title	Common Stock, par value of $0.0001
Amount Registered \| shares	29,164,045
Proposed Maximum Offering Price per Unit	17.7597
Maximum Aggregate Offering Price	$ 517,944,689.99
Fee Rate	0.01381%
Amount of Registration Fee	$ 71,528.17
Offering Note	(A) The amount of shares registered represents an aggregate of 29,164,045 shares of common stock, par value $0.0001 per share, of Obsidian Therapeutics, Inc. (the "Common Stock"), all of which were acquired by the selling stockholders named in the prospectus that forms a part of this registration statement (this "Registration Statement") in a private placement. Pursuant to Rule 416(a) promulgated under the Securities Act of 1933, as amended (the "Securities Act"), this Registration Statement shall also cover any additional shares of Common Stock that may be offered or become issuable as a result of stock splits, stock dividends, or other distribution, recapitalization or similar event or transaction effected without the receipt of consideration which results in an increase in the number of outstanding Common Stock. (B) Estimated solely for purposes of calculating the registration fee in accordance with Rule 457(c) under the Securities Act and based upon the average of the high and low sales prices of the Common Stock, as reported on the Nasdaq Capital Market on August 27, 2026, which date is within five business days prior to the filing of this Registration Statement.

Income Taxes - Summary of Changes in the Valuation Allowance for Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Income Tax Disclosure [Abstract]
Valuation allowance at the beginning of the year	$ 67,584	$ 40,458
Increases recorded to income tax provision	30,471	27,126
Valuation allowance at end of the year	$ 98,055	$ 67,584

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
	Nov. 30, 2020	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024	Oct. 31, 2021	Jan. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Percentage Of Matching Contribution									100.00%
Percentage Of Maximum Employee Contribution To Plan Compensation									3.00%
Amount Of Matching Contribution		$ 100	$ 100	$ 300	$ 300	$ 500	$ 500
Amount Funded To Research Activities	$ 8,300
Clinical And Regulatory Milestones Payments								$ 75,000
Specified Sales Milestones Payments								$ 90,000
Amount Of Additional Milestone Payments On Achievement		0		0		0
Liability Recognised In Relation To Milestone Achievement		$ 0		$ 0		$ 0

Lease - Summary of Components of Operating Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Lease, Cost [Abstract]
Operating lease cost	$ 700	$ 700	$ 1,400	$ 1,400	$ 2,757	$ 2,757
Variable operating lease cost					541	516
Total operating lease cost					$ 3,298	$ 3,273

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024
Current assets:
Cash and cash equivalents	$ 17,983	$ 40,405	$ 49,761
Marketable securities	16,462	40,081	118,509
Prepaid expenses and other current assets	11,914	1,030	4,578
Total current assets	46,359	81,516	172,848
Property and equipment, net	1,201	1,911	3,322
Right-of-use assets	2,878	4,149	6,539
Restricted cash	1,004	1,004	1,004
Total assets	51,442	88,580	183,713
Current liabilities:
Accounts payable	365	12	1,818
Accrued expenses and other current liabilities	17,853	12,291	11,278
Operating lease liabilities, current portion	1,974	3,048	2,966
Financing lease liabilities	4	11	24
Total current liabilities	20,196	15,362	16,086
Operating lease liabilities, net of current portion	928	1,224	3,824
Other non-current liabilities	1	3	206
Total liabilities	21,125	16,589	20,116
Commitments and contingencies (Note 10)
Redeemable convertible preferred stock	330,028	338,028	338,028
Stockholders' deficit:
Common stock	2	1	1
Additional paid-in-capital	41,722	29,874	20,923
Accumulated other comprehensive income (loss)	(3)	23	(27)
Accumulated deficit	(341,432)	(295,935)	(195,328)
Total stockholders' deficit	(299,711)	(266,037)	(174,431)
Total liabilities, redeemable convertible preferred stock and stockholders' deficit	$ 51,442	$ 88,580	$ 183,713

Leases - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Lessee, Lease, Description [Line Items]
Operating Lease, Payments			$ 3,000		$ 2,896	$ 2,776
Operating Lease, Cost	$ 700	$ 700	$ 1,400	$ 1,400	$ 2,757	$ 2,757

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Operating expenses:
Research and development	$ 21,549	$ 22,952	$ 37,281	$ 44,078	$ 86,113	$ 73,187
General and administrative	4,591	5,307	9,139	10,784	19,554	18,068
Total operating expenses	26,140	28,259	46,420	54,862	105,667	91,255
Loss from operations	(26,140)	(28,259)	(46,420)	(54,862)	(105,667)	(91,255)
Other income, net:
Interest and other income	276	1,363	923	2,980	5,060	8,146
Total other income	276	1,363	923	2,980	5,060	8,146
Loss before income tax expense	(25,864)	(26,896)	(45,497)	(51,882)	(100,607)	(83,109)
Income tax benefit (expense)	0	0	0	0	0	0
Net loss	(25,864)	(26,896)	(45,497)	(51,882)	(100,607)	(83,109)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	2	(11)	(26)	(11)	50	(54)
Total other comprehensive income (loss)	2	(11)	(26)	(11)	50	(54)
Total comprehensive loss	$ (25,862)	$ (26,907)	$ (45,523)	$ (51,893)	$ (100,557)	$ (83,163)
Net loss per share attributable to common stockholders - Basic	$ (1.19)	$ (1.93)	$ (2.3)	$ (3.72)	$ (7.22)	$ (6.47)
Net loss per share attributable to common stockholders - Diluted	$ (1.19)	$ (1.93)	$ (2.3)	$ (3.72)	$ (7.22)	$ (6.47)
Weighted-average common shares outstanding - Basic	21,808,064	13,939,366	19,751,933	13,931,419	13,935,769	12,848,484
Weighted-average common shares outstanding - Diluted	21,808,064	13,939,366	19,751,933	13,931,419	13,935,769	12,848,484

Stock-Based Compensation

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

7. Stock-Based Compensation

2016 Equity Incentive Plan

In March 2016, the Company adopted the 2016 Stock Option and Grant Plan, or the 2016 Plan, which allows the granting of awards in the form of incentive stock options, nonqualified stock options, and stock grants, which may include restricted stock, to eligible employees, outside directors and consultants of the Company. The total number of common stock reserved for grant under the 2016 Plan was 48,749,161 shares as of June 30, 2026 and December 31, 2025, of which 5,330,455 and 4,475,263 shares remained available for future issuance as of June 30, 2026 and December 31, 2025, respectively. The 2016 Plan expired in March 2026 and no future awards may be granted thereunder. Effective immediately prior to the closing of the merger on August 3, 2026, the 2026 Equity Incentive Plan and the 2026 Employee Stock Purchase Plan became effective. Pursuant to the share reserve provisions of the 2026 Equity Incentive Plan, shares underlying outstanding awards granted under the

2016 Plan that are forfeited, canceled, expire unexercised or otherwise terminate without issuance of the underlying shares may become available for future issuance under the 2026 Equity Incentive Plan.

Stock Options


	June 30,
	2026			2025
Fair value of common stock	$	0.78-0.96		$	0.78 – 1.13
Risk-free interest rate		3.94	%		4.26	%
Expected dividend yield		—			—
Expected term (in years)		5.9			6.0
Expected volatility		82.71	%		106.25	%

The weighted average fair value of options granted during the six months ended June 30, 2026 and June 30, 2025 was $0.57 and $0.72, respectively.

The following table summarizes option activity under the 2016 Plan for the six months ended June 30, 2026:


	Number of Options			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2025		38,061,610		$	0.77		6.9	$	298
Options granted		5,353,691			0.79
Options exercised		(1,161,144	)		0.72
Options forfeited		(2,441,148	)		0.78
Options expired		(4,177,316	)		0.77

Outstanding at June 30, 2026		35,635,693		$	0.78		7.4	$	6,528

Vested and exercisable at June 30, 2026		21,465,199		$	0.77		6.7	$	4,045
Unvested at June 30, 2026		14,170,494		$	0.78		8.2	$	2,102

During the six months ended June 30, 2026, 354,074

performance-based

stock options granted in 2024 were forfeited, with approximately half forfeited due to employee termination and the remaining forfeited due to the related performance condition not being achieved. Additionally, during the six months ended June 30, 2026 the Company granted 1,883,750

performance-based

awards that vest upon the achievement of specified performance goals, with a portion subject to continued

service-based

vesting thereafter. As of June 30, 2026, the applicable performance conditions for these awards were not deemed probable, and therefore no compensation expense has been recognized related to these awards.

The aggregate intrinsic value of options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock.

The aggregate intrinsic value of options exercised totaled $0.3 million for the six months ended June 30, 2026 and less than $0.1 million for the six months ended June 30, 2025. As of June 30, 2026 there was $11.2 million of unrecognized compensation expense, which the Company expects to recognize over a weighted-average period of 2.1 years. Included in this amount is $1.0 million of unrecognized compensation expense relating to the performance-based awards described above.

The Company has recorded stock-based compensation expense as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
Research and development	$	688	$	1,168	$	1,368	$	1,993
General and administrative		864		1,593		1,638		2,878

	$1,552		$2,761		$3,006		$4,871

8. Stock-Based Compensation

2016 Equity Incentive Plan

In March 2016, the Company adopted the 2016 Stock Option and Grant Plan (the “2016 Plan”), which allows the granting of awards in the form of incentive stock options, nonqualified stock options, and stock grants, which may include restricted stock, to eligible employees, outside directors and consultants of the Company. The total number of common stock reserved for grant under the 2016 Plan was 48,749,161 shares as of December 31, 2025 and December 31, 2024, of which 4,475,263 and 1,993,987 shares remained available for future issuance as of December 31, 2025 and 2024, respectively. Shares that are expired, terminated, surrendered, or canceled without having been fully exercised will be available for future awards under the 2016 Plan.

The 2016 Plan is administered by the Company’s board of directors. The terms of stock awards agreements, including type of stock award to be granted, the provisions of each stock award, including the number of shares, vesting requirements, and exercise prices, are determined by the board of directors, and are subject to the provisions of the 2016 Plan. Option awards generally vest over a four-year period and expire after ten years. Certain options provide for accelerated vesting in the event of a change in control, as defined. The exercise price per share for stock options granted may not be less than the fair market value of the common stock at the date of grant.

Stock Options

The Company has granted stock options with service-based vesting conditions, performance-based, and with both service and performance-based vesting conditions. The Company typically grants stock options to employees and nonemployees at exercise prices deemed by the Board to be equal to the fair value of the common stock at the time of grant. Stock options typically vest over four years and have a maximum term of ten years.


	December 31,
	2025			2024
Fair value of common stock	$	0.78 – 1.13		$	1.01 – 1.13
Risk-free interest rate		3.94	%		4.25	%
Expected dividend yield		—			—
Expected term (in years)		6.1			6.1
Expected volatility		89.54	%		133.20	%

The weighted average fair value of options granted during the years ended December 31, 2025 and 2024 was $0.62 and $1.03, respectively.

The following table summarizes option activity under the 2016 Plan for the year ended December 31, 2025:


	Number of Options			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2024		40,628,032		$	1.03		8.4	$	4,146
Options granted		432,000			0.78
Options exercised		(20,146	)		0.97
Options forfeited		(2,530,814	)		1.05
Options expired		(447,462	)		1.00

Outstanding at December 31, 2025		38,061,610		$	0.77		6.9	$	298

Vested and exercisable at December 31, 2025		23,056,967		$	0.77		6.1	$	298
Unvested at December 31, 2025		15,004,643		$	0.78		8.2	$	—

Included within the total stock options outstanding at December 31, 2025, are 2,027,700 stock options to purchase common stock which have either both performance and service-based vesting criteria or performance only vesting criteria (collectively, the “Performance Awards”) and were granted to certain employees and officers during 2023 and 2024. Of the total 2,027,700 Performance Awards outstanding: (i) 1,231,034 outstanding stock options were granted in 2023 and had performance criteria tied to the achievement of three scientific milestones, each followed by two years of service vesting. Expense was recognized when achievement became probable. As of December 31, 2025, all three milestones associated with this grant had either been achieved or partially achieved; (ii) 442,592 outstanding stock options were granted in 2023 and had performance criteria tied to the completion of a strategic transaction, which was achieved upon the close of the Series C Preferred Stock financing in March 2024, and therefore the grant date fair value of the stock options was expensed in full upon achievement of the financing; and (iii) 354,074 outstanding stock options were granted in 2024 and had performance criteria tied to the achievement of strategic milestones of the Company along with service-based vesting conditions. As of December 31, 2025, the performance milestones have not yet been achieved and are not deemed probable of being achieved. Total stock-based compensation expense associated with performance stock options was $0.2 million and $0.7 million during the years ended December 31, 2025 and 2024, respectively.

The aggregate intrinsic value of options exercised for each of the years ended December 31, 2025 and 2024 totaled zero and $0.8 million, respectively. As of December 31, 2025 there was $13.3 million of unrecognized compensation expense, which the Company expects to recognize over a weighted-average period of 2.03 years.

The Company has recorded stock-based compensation expense as follows (in thousands):


	December 31,
	2025		2024
Research and development	$	3,733	$	2,938
General and administrative		5,198		4,122

	$	8,931	$	7,060

Redeemable Convertible Preferred Stock

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Equity [Abstract]

Redeemable Convertible Preferred Stock

5. Redeemable Convertible Preferred Stock

In February 2026, Takeda Ventures, Inc., elected to convert 7,085,290 shares of Series

A-1

Preferred Stock into Common Stock ,par value $0.0001 per share (“Common Stock”) at the conversion price of $1.1291.

At June 30, 2026 and December 31, 2025, the Preferred Stock is summarized below (in thousands, except share amounts):


	Amounts at June 30, 2026
	Total Shares Authorized		Total Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion
Series A-1 Preferred Stock		33,222,339		26,114,925	$	29,486	$	29,486		26,114,925
Series A-2 Preferred Stock		14,936,323		14,936,323		16,807		14,936		14,936,323
Series A-3 Preferred Stock		6,146,592		6,146,592		9,035		9,035		6,146,592
Series B Preferred Stock		76,187,917		76,187,917		114,732		115,044		76,187,917
Series C Preferred Stock		84,567,145		84,567,145		159,968		160,500		84,567,145

Total		215,060,316		207,952,902	$	330,028	$	329,001		207,952,902


	Amounts at December 31, 2025
	Total Shares Authorized		Total Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion
Series A-1 Preferred Stock		33,222,339		33,200,215	$	37,486	$	37,486		33,200,215
Series A-2 Preferred Stock		14,936,323		14,936,323		16,807		14,936		14,936,323
Series A-3 Preferred Stock		6,146,592		6,146,592		9,035		9,035		6,146,592
Series B Preferred Stock		76,187,917		76,187,917		114,732		115,044		76,187,917
Series C Preferred Stock		84,567,145		84,567,145		159,968		160,500		84,567,145

Total		215,060,316		215,038,192	$	338,028	$	337,001		215,038,192

There has been no change to the rights and preferences of the Preferred Stock. Refer to the notes to the consolidated financial statements, for the year ended December 31, 2025 for a detailed discussion of the rights and preferences of the Preferred Stock.

6. Redeemable Convertible Preferred Stock

The Company has issued Series

A-1

redeemable convertible preferred stock (the “Series

A-1

Preferred Stock”), Series

A-2

redeemable convertible preferred stock (the “Series

A-2

Preferred Stock”), Series

A-3

redeemable convertible preferred stock, (the “Series

A-3

Preferred Stock”), Series B redeemable convertible preferred stock (the “Series B Preferred Stock”) and Series C redeemable convertible preferred stock (the “Series C Preferred Stock”); collectively referred to as the “Preferred Stock” and the holders of the Preferred Stock as the “Preferred Stockholders.” All series of Preferred Stock have a par value of

0.0001

In March 2024, the Company entered into a stock purchase agreement (the “Series C Purchase Agreement”) pursuant to which the Company issued and sold an aggregate of 84,567,145 shares of Series C Preferred Stock at a price of $1.8979 per share, for gross proceeds of approximately $160.5 million and incurred issuance costs of $0.5 million.

Upon issuance of each class of Preferred Stock, the Company assessed the embedded conversion and liquidation features of the shares and determined that such features did not require the Company to separately account for these features. The Company also concluded that no beneficial conversion feature existed on the issuance dates of each class of Preferred Stock.

At December 31, 2025 and 2024, the Preferred Stock is summarized below (in thousands, except share amounts):


	Amounts at December 31, 2025 and December 31, 2024
	Total Shares Authorized		Total Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion
Series A-1 Preferred Stock		33,222,339		33,200,215	$	37,486	$	37,486		33,200,215
Series A-2 Preferred Stock		14,936,323		14,936,323		16,807		14,936		14,936,323
Series A-3 Preferred Stock		6,146,592		6,146,592		9,035		9,035		6,146,592
Series B Preferred Stock		76,187,917		76,187,917		114,732		115,044		76,187,917
Series C Preferred Stock		84,567,145		84,567,145		159,968		160,500		84,567,145

Total		215,060,316		215,038,192	$	338,028	$	337,001		215,038,192

The rights and preferences of the Preferred Stock are as follows:

Voting Rights

The Preferred Stockholders vote on an

as-converted

basis with holders of common stock on all general matters. Additionally, holders of Series A Preferred Stock, Series B Preferred Stock, and Series C Preferred Stock each have the exclusive right to elect one director per series, voting separately as a class. Holders of Series

A-3

Preferred Stock, Series B Preferred Stock, and Series C Preferred Stock also hold series-specific protective voting rights requiring their separate approval for certain amendments or capital structure actions, and all Preferred Stockholders voting together as a single class (with a required majority of holders of Series C Preferred Stock included) must approve major corporate actions such as liquidation events, charter amendments affecting rights of Preferred Stockholders, creation of senior or junior securities, certain indebtedness, and other key matters.

Dividend Rights

The Preferred Stockholders are entitled to receive, prior to the payment of any dividend on the common stock, a dividend on each outstanding share of preferred stock on an as converted to common stock basis immediately prior to the record date. Any such dividends shall be payable only when, as, and if declared by the Company’s board of directors. No dividends have been declared through December 31, 2025.

Liquidation Preference

The Series C Preferred Stock ranks senior to the Series B Preferred Stock, Series A Preferred Stock and Common Stock of the Company. In the event of a liquidation of the Company, or certain deemed liquidation events, the Series C is redeemable for a price equal to the greater of (i) Series C Original Issue Price of $1.8979 per share, plus any dividends declared but unpaid, or (ii) such amount per share as would have been payable had all Series C Preferred Stock converted into common stock immediately prior to the liquidation or deemed liquidation. If assets or surplus remain after satisfying the Series C Preferred Stockholders, the Series B Preferred Stock is redeemable for a price equal to the greater of (i) Series B Original Issue Price of $1.51 per share, plus any dividends declared but unpaid, or (ii) such amount per share as would have been payable had all Series B Preferred Stock converted into common stock immediately prior to the liquidation or deemed liquidation. If assets or surplus remain after satisfying the Series B Preferred Stockholders, the Series A Preferred Stockholders is redeemable for a price equal to the greater of (i) Series

A-1,

Series

A-2,

and Series

A-3

Original Issue Price of $1.1291, $1.00, and $1.47 per share, respectively, plus any dividends declared but unpaid, or (ii) such amount per share as would have been payable had all Series

A-1,

A-2

and

A-3

Preferred Stock converted into common stock immediately prior to the liquidation or deemed liquidation.

In the event of a liquidation event or deemed liquidation, if the assets or surplus funds to be distributed to the holders of Series C Preferred Stock, are insufficient to permit the payment to such holders of their full aggregate distribution due, the assets and surplus legally available for distribution shall be distributed ratably among the holders of Series C Preferred Stock in proportion to the full aggregate Series C distributions each such holder is otherwise entitled to receive. After distribution to Series C Preferred Stockholders the same distribution would take place to Series B Preferred Stockholders if any assets or surplus remain. After distribution to Series B Preferred Stockholders the same distribution would take place to Series A Preferred Stockholders if any assets or surplus remain. No payment shall be made with respect to the common stock unless and until full payment has been made to the holders of the Series C Preferred Stock, Series B Preferred Stock and Series A Preferred Stock of the distribution amounts that they are entitled to receive.

Redemption Rights

The Preferred Stockholders do not have redemption rights, except upon a Deemed Liquidation Event.

Conversion

Optional Conversion

Each share of Preferred Stock, at the option of the holder, is convertible into a number of fully paid shares of common stock as determined by dividing issue price by the conversion price in effect at the time. The initial conversion price per share for Series

A-1,

Series

A-2

and Series

A-3

Preferred Stock is $1.1291, $1.00, and

$1.47, respectively, the Series B Preferred Stock initial conversion price is $1.51 per share and the Series C Preferred Stock initial conversion price if $1.8979. Such initial conversion prices, and the rate at which shares of Preferred Stock may be converted into shares of common stock, shall be subject to adjustment as provided in the Company’s fourth amended and restated certificate of incorporation.

Mandatory Conversion

All outstanding shares of Preferred Stock will automatically convert into a number of fully paid shares of common stock at the then applicable conversion price upon the completion of either (i) the closing of the sale of shares of common stock to the public in a sale price of at least $2.8469 per share resulting in gross proceeds to the Company of at least $100.0 million (“Qualified IPO”) or; (ii) the direct listing on a nationally recognized stock exchange with a reference price of at least $2.8469 per share or; (iii) a special purpose acquisition company (“SPAC”) transaction or reverse merger transaction resulting in a sale price of at least $2.8469 per share or; (iv) other event that results in the Company or its successor in interest having its common equity listed for trading on a nationally recognized stock exchange with a share price of at least $2.8469 per share or upon the vote or written consent of a majority of holders of the then outstanding shares of Preferred Stock voting together as a single class on an

as-converted

to common stock basis.

Subsequent Events	6 Months Ended	12 Months Ended
Subsequent Events	Jun. 30, 2026	Dec. 31, 2025
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events The Company has evaluated subsequent events through August 14, 2026, the date these condensed consolidated financial statements were issued, and determined that there have been no events that have occurred that would require adjustments to the Company’s disclosures in the condensed consolidated financial statements, except for the following: Galera Transaction On August 3, 2026, Gazelle Parent, Inc. (“Parent”) completed the previously announced mergers pursuant to the Agreement and Plan of the Merger (the “Merger Agreement”) dated April 14, 2026, by and among Parent, the Company, Onyx MergerSub, Inc., Gazelle Merger Subsidiary, Inc. and Galera, such that Parent, who subsequently changed its name to Obsidian Therapeutics, Inc., became the parent of two wholly owned subsidiaries, Obsidian Therapeutics Sub, Inc. (formerly Obsidian Therapeutics, Inc. (“Legacy Obsidian”)) and Galera Therapeutics, Inc. (“Legacy Galera”). In connection with the closing of the transaction, all outstanding shares of the Legacy Obsidian preferred stock and outstanding warrants were converted into shares of Legacy Obsidian common stock, which were subsequently converted into shares of Parent common stock calculated as defined in the Merger Agreement. Additionally, each outstanding and unexercised option to purchase Legacy Obsidian shares was converted into an option to purchase shares of Parent common stock, with necessary adjustments to the number of shares and exercise price pursuant to the terms of the Merger Agreement. Concurrently with entering into the Merger Agreement, on April 14, 2026, Parent, Legacy Obsidian and Legacy Galera entered into a securities purchase agreement (the “Securities Purchase Agreement”), with certain qualified institutional buyers and/or accredited investors (the “Investors”). Pursuant to the Securities Purchase Agreement, and subject to the terms and conditions therein, the Investors agreed to purchase, and Legacy Galera agreed to issue and sell, immediately prior to the effective time of the Obsidian Merger (the “Obsidian Effective Time”), shares of Legacy Galera’s Series C Non-Voting Convertible Preferred Stock, par value $0.001 per share (“Series C Preferred Stock”), for an aggregate purchase price of $350.0 million (the “Concurrent PIPE Financing”). The Concurrent PIPE Financing closed on July 31, 2026. In connection with the Concurrent PIPE Financing, Parent and Legacy Galera and the investors in the Concurrent PIPE Financing entered into a registration rights agreement (the “Registration Rights Agreement”), pursuant to which, among other things, the Company agreed to register for resale certain shares of common stock of Parent, par value $ 0.0001 per share (“Parent Common Stock”) held by such Investors from time to time, including shares of Parent Common Stock issued in the Mergers in exchange for the shares of common stock, par value $0.001 per share, of Legacy Galera (“Legacy Galera Common Stock”) issued in the Concurrent PIPE Financing. On August 3, 2026, Parent and Legacy Obsidian entered into a Contingent Value Rights Agreement (the “CVR Agreement”) with Equiniti Trust Company, LLC (the “Rights Agent”), pursuant to which stockholders of Legacy Galera of record as of July 31, 2026 received (1) one contingent value right, each a CVR, for each outstanding share of Legacy Galera Common Stock held by such stockholder on such date, representing the right to receive a pro rata portion of 80% of any potential future net proceeds received by Parent or its affiliates from the development, commercialization, licensing, sale or other disposition of the Legacy Product (as defined in the CVR Agreement), or related intellectual property during the five years following the closing and (2) the CVR for each outstanding share of Legacy Galera Common Stock held by such stockholder on such date, representing the right to receive a pro rata portion of 95% of any potential future net proceeds received by Parent or its affiliates from the Supportive-Care Product Divestiture (as defined in the CVR Agreement) during the ten years following the closing. Parent began trading on the Nasdaq Capital Market under the ticker symbol “OBX” on August 4, 2026.	15. Subsequent Events The Company has evaluated subsequent events through April 22, 2026, the date these consolidated financial statements were issued, and determined that there have been no events that have occurred that would require adjustments to the Company’s disclosures in the consolidated financial statements, except for the following: Conversion of Series A-1 Preferred Stock In February 2026, a holder of the Company’s Series A-1 Preferred Stock delivered a notice electing to convert 7,085,290 shares of its Series A-1 Preferred Stock into an equivalent number of shares of the Company’s common stock on a one-for-one basis, in accordance with the conversion provisions of the Company’s fourth amended and restated certificate of incorporation. The conversion was effective upon the Company’s receipt of the notice and was not subject to any conditions. Following the conversion, 7,085,290 shares of Series A-1 Preferred Stock were cancelled, and an equal number of common shares were issued to such holder.

Segment Information - Schedule of Significant Segment Expenses and Segment Operating Loss (Details) - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

12 Months Ended

Jun. 30, 2026

Jun. 30, 2025

Jun. 30, 2026

Jun. 30, 2025

Dec. 31, 2025

Dec. 31, 2024

Segment Reporting [Abstract]

Revenues

$ 0

Research and Development Expense [Abstract]

Compensation and related expenses

5,486

^[1]

7,067

^[1]

10,734

^[1]

13,156

^[1]

21,828

^[2]

24,537

^[2]

Drug discovery and platform

^[1]

417

^[1]

249

^[1]

567

^[1]

1,026

^[2]

844

^[2]

Clinical and manufacturing activities

12,637

^[1]

12,428

^[1]

20,448

^[1]

24,447

^[1]

52,065

^[2]

36,831

^[2]

Occupancy and all other costs

2,687

^[1]

1,872

^[1]

4,482

^[1]

3,915

^[1]

7,461

^[2]

8,037

^[2]

Total research and development expense

20,861

21,784

35,913

42,085

82,380

70,249

General and Administrative Expense [Abstract]

Compensation and related expenses

2,096

^[3]

2,228

^[3]

4,359

^[3]

4,576

^[3]

8,174

^[4]

7,912

^[4]

Consulting and professional services

1,244

^[3]

1,010

^[3]

2,441

^[3]

2,249

^[3]

4,382

^[4]

4,791

^[4]

Occupancy and all other costs

387

^[3]

475

^[3]

701

^[3]

1,081

^[3]

1,800

^[4]

1,243

^[4]

Total general and administrative expense

3,727

3,713

7,501

7,906

14,356

13,946

Stock-based compensation

1,552

2,762

3,006

4,871

8,931

7,060

Other segment items

^[5]

(276)

(1,363)

(923)

(2,980)

(5,060)

(8,146)

Net loss

$ 25,864

$ 26,896

$ 45,497

$ 51,882

$ (100,607)

$ (83,109)

[1]	Research and development expense excludes stock-based compensation expense, which is presented separately below. Stock-based compensation expense excluded from research and development expense was $0.7 million and $1.2 million for the three months ended June 30, 2026 and 2025, respectively, and $1.4 million and $2.0 million for the six months ended June 30, 2026 and 2025, respectively.
[2]	Research and development expense for the years ended December 31, 2025 and 2024 exclude $3.7 million and $2.9 million of stock-based compensation expense, respectively, which is presented separately below.
[3]	General and administrative expense excludes stock-based compensation expense, which is presented separately below. Stock-based compensation expense excluded from general and administrative expense was $0.8 million and $1.6 million for the three months ended June 30, 2026 and 2025, respectively, and $1.6 million and $2.9 million for the six months ended June 30, 2026 and 2025, respectively.
[4]	General & administrative expense for the years ended December 31, 2025 and 2024 exclude $5.2 million and $4.1 million of stock-based compensation expense, respectively, which is presented separately below.
[5]	Other segment items include interest and other income, net.

Financial Instruments and Fair Value Measurements - Schedule of Roll Forward of Fair Value of the Level 3 Preferred Stock Warrant Liability (Details) - Preferred Stock Warrant Liability [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Roll Forward Of Fair Value Of The Level3 Preferred Stock Warrant Liability [Line Items]
Fair value, beginning of year	$ 6	$ 14
Change in estimated fair value	(3)	(8)
Fair value, end of year	$ 3	$ 6

Nature of the Business and Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands			12 Months Ended
	Jul. 31, 2026	Apr. 14, 2026	Dec. 31, 2025	Jun. 30, 2026	Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Marketable securities			$ 80,500	$ 34,400
Accumulated deficit			295,935	$ 341,432	$ 195,328
Net cash used in operating			$ 90,400
Expected gross proceeds from private placement financing		$ 350,000
Proceeds from Issuance of Common Stock	$ 350,000

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S45
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480100/505-10-S45-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477657/942-210-S45-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478478/942-210-S50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(21))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30)(a)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 852
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481372/852-10-55-10

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480016/944-40-65-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (h)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480016/944-40-65-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-11

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(23)(a)(4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(17))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1

+ Details

Net Loss Per Share - Schedule of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	243,610,719	254,307,665	253,121,926	255,688,348
Redeemable Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	207,952,902	215,038,192	215,038,192	215,038,192
Warrants to purchase Series A-1 redeemable convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	22,124	22,124	22,124	22,124
Common Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	35,635,693	39,247,349	38,061,610	40,628,032

Property and Equipment, Net

12 Months Ended

Dec. 31, 2025

Property, Plant, and Equipment [Abstract]

Property and Equipment, Net

4. Property and Equipment, Net

Property and equipment, net, are recorded at historical cost and consist of the following (in thousands):


	December 31,
	2025			2024
Laboratory equipment	$	10,017		$	9,944
Leasehold improvements		261			261
Furniture and fixtures		758			758
Computer software		385			385

Total property and equipment		11,421			11,348
Less: accumulated depreciation		(9,510	)		(8,026	)

Property and equipment, net	$	1,911		$	3,322

Depreciation expense amounted to $1.5 million for each of the years ended December 31, 2025 and 2024.

- Definition

The entire disclosure for property, plant, and equipment. Includes, but is not limited to, land and land improvement; building; machinery and equipment; furniture and fixture; and work of art, historical treasure, or similar asset classified as collection.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482099/360-10-50-3

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482099/360-10-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 360
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/360/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482099/360-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482130/360-10-45-13

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 5.CC)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480091/360-10-S99-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-SubTopic 360
-Topic 958
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477798/958-360-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-SubTopic 360
-Topic 958
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477798/958-360-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-SubTopic 360
-Topic 958
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477798/958-360-50-7

+ Details

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Cash flows from operating activities:
Net loss	$ (45,497)	$ (51,882)	$ (100,607)	$ (83,109)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	635	752	1,484	1,527
Stock-based compensation expense	3,006	4,871	8,931	7,060
Change in fair value of preferred stock warrant liability	(2)	2	(3)	(8)
Accretion of discount on marketable securities	(407)	(1,621)	(2,612)	(2,207)
Loss on sale of property and equipment	56	0
Non-cash lease expense	(106)	(67)	(141)	(17)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(10,884)	3,370	3,548	(2,733)
Accounts payable	353	(1,339)	(1,806)	701
Accrued expenses and other current liabilities	5,562	250	1,013	3,584
Other non-current liabilities	0	(200)	(200)	200
Net cash used in operating activities	(47,284)	(45,864)	(90,393)	(75,002)
Cash flows from investing activities:
Purchases of property and equipment	0	(57)	(73)	(779)
Purchases of marketable securities	0	(36,192)	(80,910)	(131,095)
Maturities of marketable securities	24,000	67,000	162,000	78,000
Proceeds from the sale of property and equipment	19	0
Net cash provided by investing activities	24,019	30,751	81,017	(53,874)
Cash flows from financing activities:
Proceeds from the exercise of stock options	843	18	20	2,547
Proceeds from Series C financing			0	160,500
Payment of Series C issuance costs			0	(532)
Net cash provided by financing activities	843	18	20	162,515
Net decrease in cash and cash equivalents and restricted cash	(22,422)	(15,095)	(9,356)	(33,639)
Cash and cash equivalents and restricted cash at beginning of period	41,409	50,765	50,765	17,126
Cash and cash equivalents and restricted cash at end of period	$ 18,987	$ 35,670	$ 41,409	$ 50,765

CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2024 USD ($)
Series C Preferred Stock [Member]
Stock issuance costs	$ 532

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024
Aggregate liquidation preference	$ 329,001	$ 337,001	$ 337,001
Common stock, par or stated value per share	$ 0.0001	$ 0.0001	$ 0.0001
Common stock, shares authorized	274,320,131	274,320,131	274,320,131
Common stock, shares, issued	22,188,335	13,941,901	13,921,755
Common stock, shares, outstanding	22,188,335	13,941,901	13,921,755

- Definition

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480100/505-10-S45-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477657/942-210-S45-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478478/942-210-S50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(20))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.6-05(4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479170/946-210-S99-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(4)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(16)(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(7))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3

+ Details

- Definition

The aggregate liquidation preference (or restrictions) of stock classified as temporary equity that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

+ References + Details

Redeemable Convertible Preferred Stock (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Equity [Abstract]

Summary of Preferred Stock Is Summarized

At June 30, 2026 and December 31, 2025, the Preferred Stock is summarized below (in thousands, except share amounts):


	Amounts at June 30, 2026
	Total Shares Authorized		Total Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion
Series A-1 Preferred Stock		33,222,339		26,114,925	$	29,486	$	29,486		26,114,925
Series A-2 Preferred Stock		14,936,323		14,936,323		16,807		14,936		14,936,323
Series A-3 Preferred Stock		6,146,592		6,146,592		9,035		9,035		6,146,592
Series B Preferred Stock		76,187,917		76,187,917		114,732		115,044		76,187,917
Series C Preferred Stock		84,567,145		84,567,145		159,968		160,500		84,567,145

Total		215,060,316		207,952,902	$	330,028	$	329,001		207,952,902


	Amounts at December 31, 2025
	Total Shares Authorized		Total Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion
Series A-1 Preferred Stock		33,222,339		33,200,215	$	37,486	$	37,486		33,200,215
Series A-2 Preferred Stock		14,936,323		14,936,323		16,807		14,936		14,936,323
Series A-3 Preferred Stock		6,146,592		6,146,592		9,035		9,035		6,146,592
Series B Preferred Stock		76,187,917		76,187,917		114,732		115,044		76,187,917
Series C Preferred Stock		84,567,145		84,567,145		159,968		160,500		84,567,145

Total		215,060,316		215,038,192	$	338,028	$	337,001		215,038,192

At December 31, 2025 and 2024, the Preferred Stock is summarized below (in thousands, except share amounts):


	Amounts at December 31, 2025 and December 31, 2024
	Total Shares Authorized		Total Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion
Series A-1 Preferred Stock		33,222,339		33,200,215	$	37,486	$	37,486		33,200,215
Series A-2 Preferred Stock		14,936,323		14,936,323		16,807		14,936		14,936,323
Series A-3 Preferred Stock		6,146,592		6,146,592		9,035		9,035		6,146,592
Series B Preferred Stock		76,187,917		76,187,917		114,732		115,044		76,187,917
Series C Preferred Stock		84,567,145		84,567,145		159,968		160,500		84,567,145

Total		215,060,316		215,038,192	$	338,028	$	337,001		215,038,192

Property and Equipment, Net (Table)

12 Months Ended

Dec. 31, 2025

Property, Plant, and Equipment [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net, are recorded at historical cost and consist of the following (in thousands):


	December 31,
	2025			2024
Laboratory equipment	$	10,017		$	9,944
Leasehold improvements		261			261
Furniture and fixtures		758			758
Computer software		385			385

Total property and equipment		11,421			11,348
Less: accumulated depreciation		(9,510	)		(8,026	)

Property and equipment, net	$	1,911		$	3,322

Leases

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Leases [Abstract]

Leases

10. Leases

The Company has

non-cancelable

operating lease agreements for office space in Cambridge, Massachusetts and Bedford, Massachusetts, which run through January 2027 and December, 2028, respectively. Future minimum payments under these operating leases as of June 30, 2026 was $3.0 million. Operating lease cost was $0.7 million for each of the three months ended June 30, 2026 and 2025, and $1.4 million for each of the six months ended June 30, 2026 and 2025.

11. Leases

The Company leases laboratory and office space in Cambridge, Massachusetts under an operating lease with a term expiring in January 2027.

Additionally, the Company leases office space in Bedford, Massachusetts under an operating lease with a term expiring in December 2028. During the year ended December 31, 2025, and 2024, the components of operating lease cost were as follows, and are reflected in general and administrative expenses and research and development expenses, as determined by the underlying activities (in thousands):


	December 31,
	2025		2024
Lease cost
Operating lease cost	$	2,757	$	2,757
Variable operating lease cost		541		516

Total operating lease cost	$	3,298	$	3,273

The following table summarizes information related to the measurement of the Company’s operating leases for the years ended December 31, 2025 and 2024 (in thousands):


	December 31,
	2025			2024
Weighted-average remaining lease term (years)		1.90			2.80
Weighted-average discount rate		6.82	%		7.13	%
Cash paid for amounts included in the measurement of operating lease liabilities	$	2,896		$	2,776

Maturities of the Company’s operating lease liabilities at December 31, 2025 are as follows (in thousands):


2026	$	2,976
2027		855
2028		673

Total minimum lease payments		4,504
Less: Interest portion		(232	)

Total present value of operating lease liabilities	$	4,272

Accrued Expenses and Other Current Liabilities (Table)

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Accrued Liabilities and Other Liabilities [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following (in thousands):


	June 30, 2026		December 31, 2025
Compensation and benefits	$	2,536	$	3,830
External research and development costs		7,722		6,361
Legal and professional fees		5,392		685
Other		2,203		1,415

Total accrued expenses and other current liabilities	$	17,853	$	12,291

Accrued expenses and other current liabilities consist of the following (in thousands):


	December 31,
	2025		2024
Compensation and benefits	$	3,830	$	5,560
External research and development costs		6,361		3,959
Legal and professional fees		685		780
Other		1,415		979

Total accrued expenses and other current liabilities	$	12,291	$	11,278

CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT - USD ($) $ in Thousands	Total	Preferred Stock [Member] Redeemable Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning balance, shares at Dec. 31, 2023		130,471,047	10,877,392
Beginning balance,value at Dec. 31, 2023		$ 178,060
Beginning balance at Dec. 31, 2023	$ (100,875)		$ 1	$ 11,316	$ 27	$ (112,219)
Issuance of common stock upon exercise of stock options - Shares			3,044,363
Issuance of common stock upon exercise of stock options - Value	2,547			2,547
Sale of Series C preferred stock, net of issuance costs - Shares		84,567,145
Sale of Series C preferred stock, net of issuance costs - Value		$ 159,968
Stock-based compensation	7,060			7,060
Unrealized gain (loss) on marketable securities	(54)				(54)
Net loss	(83,109)					(83,109)
Ending balance at Dec. 31, 2024	(174,431)		$ 1	20,923	(27)	(195,328)
Ending balance,value at Dec. 31, 2024	338,028	$ 338,028
Ending balance, shares at Dec. 31, 2024		215,038,192	13,921,755
Issuance of common stock upon exercise of stock options - Shares			17,611
Issuance of common stock upon exercise of stock options - Value	6			6
Stock-based compensation	2,110			2,110
Net loss	(24,986)					(24,986)
Ending balance at Mar. 31, 2025	(197,301)		$ 1	23,039	(27)	(220,314)
Ending balance,value at Mar. 31, 2025		$ 338,028
Ending balance, shares at Mar. 31, 2025		215,038,192	13,939,366
Beginning balance, shares at Dec. 31, 2024		215,038,192	13,921,755
Beginning balance,value at Dec. 31, 2024	338,028	$ 338,028
Beginning balance at Dec. 31, 2024	(174,431)		$ 1	20,923	(27)	(195,328)
Unrealized gain (loss) on marketable securities	(11)
Net loss	(51,882)
Ending balance at Jun. 30, 2025	(221,435)		$ 1	25,812	(38)	(247,210)
Ending balance,value at Jun. 30, 2025		$ 338,028
Ending balance, shares at Jun. 30, 2025		215,038,192	13,939,366
Beginning balance, shares at Dec. 31, 2024		215,038,192	13,921,755
Beginning balance,value at Dec. 31, 2024	338,028	$ 338,028
Beginning balance at Dec. 31, 2024	$ (174,431)		$ 1	20,923	(27)	(195,328)
Issuance of common stock upon exercise of stock options - Shares	20,146		20,146
Issuance of common stock upon exercise of stock options - Value	$ 20			20
Stock-based compensation	8,931			8,931
Unrealized gain (loss) on marketable securities	50				50
Net loss	(100,607)					(100,607)
Ending balance at Dec. 31, 2025	(266,037)		$ 1	29,874	23	(295,935)
Ending balance,value at Dec. 31, 2025	338,028	$ 338,028
Ending balance, shares at Dec. 31, 2025		215,038,192	13,941,901
Beginning balance, shares at Mar. 31, 2025		215,038,192	13,939,366
Beginning balance,value at Mar. 31, 2025		$ 338,028
Beginning balance at Mar. 31, 2025	(197,301)		$ 1	23,039	(27)	(220,314)
Issuance of common stock upon exercise of stock options - Shares			0
Issuance of common stock upon exercise of stock options - Value	12			12
Stock-based compensation	2,761			2,761
Unrealized gain (loss) on marketable securities	(11)			0	(11)
Net loss	(26,896)					(26,896)
Ending balance at Jun. 30, 2025	(221,435)		$ 1	25,812	(38)	(247,210)
Ending balance,value at Jun. 30, 2025		$ 338,028
Ending balance, shares at Jun. 30, 2025		215,038,192	13,939,366
Beginning balance, shares at Dec. 31, 2025		215,038,192	13,941,901
Beginning balance,value at Dec. 31, 2025	338,028	$ 338,028
Beginning balance at Dec. 31, 2025	(266,037)		$ 1	29,874	23	(295,935)
Issuance of common stock upon exercise of stock options - Shares			59,937
Issuance of common stock upon exercise of stock options - Value	47			47
Stock-based compensation	1,454			1,454
Conversion of Series A Preferred Stock,Share		(7,085,290)	7,085,290
Conversion of Series A Preferred Stock	8,000	$ (8,000)	$ 1	7,999
Unrealized gain (loss) on marketable securities	(28)				(28)
Net loss	(19,633)					(19,633)
Ending balance at Mar. 31, 2026	(276,197)		$ 2	39,374	(5)	(315,568)
Ending balance,value at Mar. 31, 2026		$ 330,028
Ending balance, shares at Mar. 31, 2026		207,952,902	21,087,128
Beginning balance, shares at Dec. 31, 2025		215,038,192	13,941,901
Beginning balance,value at Dec. 31, 2025	338,028	$ 338,028
Beginning balance at Dec. 31, 2025	$ (266,037)		$ 1	29,874	23	(295,935)
Issuance of common stock upon exercise of stock options - Shares	1,161,144
Unrealized gain (loss) on marketable securities	$ (26)
Net loss	(45,497)
Ending balance at Jun. 30, 2026	(299,711)		$ 2	41,722	(3)	(341,432)
Ending balance,value at Jun. 30, 2026	330,028	$ 330,028
Ending balance, shares at Jun. 30, 2026		207,952,902	22,188,335
Beginning balance, shares at Mar. 31, 2026		207,952,902	21,087,128
Beginning balance,value at Mar. 31, 2026		$ 330,028
Beginning balance at Mar. 31, 2026	(276,197)		$ 2	39,374	(5)	(315,568)
Issuance of common stock upon exercise of stock options - Shares			1,101,207
Issuance of common stock upon exercise of stock options - Value	796			796
Stock-based compensation	1,552			1,552
Unrealized gain (loss) on marketable securities	2				2
Net loss	(25,864)					(25,864)
Ending balance at Jun. 30, 2026	(299,711)		$ 2	$ 41,722	$ (3)	$ (341,432)
Ending balance,value at Jun. 30, 2026	$ 330,028	$ 330,028
Ending balance, shares at Jun. 30, 2026		207,952,902	22,188,335

Segment Information (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Segment Reporting [Abstract]

Schedule of Significant Segment Expenses and Segment Operating Loss

The following tables illustrate information about segment revenue, significant segment expenses and segment operating loss for the three and six months ended June 30, 2026 and 2025:


	Three Months Ended June 30,						Six Months Ended June 30,
	2026			2025			2026			2025
Revenues:	$	—		$	—		$	—		$	—
Less(1):
Research and development expenses(2):
Compensation and related expenses		5,486			7,067			10,734			13,156
Drug discovery and platform		51			417			249			567
Clinical and manufacturing activities		12,637			12,428			20,448			24,447
Occupancy and all other costs		2,687			1,872			4,482			3,915

Total research and development expense	$	20,861		$	21,784		$	35,913		$	42,085
General and administrative expenses(3):
Compensation and related expenses		2,096			2,228			4,359			4,576
Consulting and professional services		1,244			1,010			2,441			2,249
Occupancy and all other costs		387			475			701			1,081

Total general and administrative expense	$	3,727		$	3,713		$	7,501		$	7,906
Stock-based compensation		1,552			2,762			3,006			4,871
Other segment items(4)		(276	)		(1,363	)		(923	)		(2,980	)

Net loss	$	25,864		$	26,896		$	45,497		$	51,882

(1)	The significant expense categories and amounts align with the segment-level information that is regularly provided to the chief operating decision maker.

(2)

Research and development expense excludes stock-based compensation expense, which is presented separately below. Stock-based compensation expense excluded from research and development expense was $0.7 million and $1.2 million for the three months ended June 30, 2026 and 2025, respectively, and $1.4 million and $2.0 million for the six months ended June 30, 2026 and 2025, respectively.

(3)

General and administrative expense excludes stock-based compensation expense, which is presented separately below. Stock-based compensation expense excluded from general and administrative expense was $0.8 million and $1.6 million for the three months ended June 30, 2026 and 2025, respectively, and $1.6 million and $2.9 million for the six months ended June 30, 2026 and 2025, respectively.

(4)	Other segment items include interest and other income, net.

The following tables illustrate information about segment revenue, significant segment expenses and segment operating loss for the years ended December 31, 2025 and 2024 (in thousands):


	Year Ended December 31,
	2025			2024
Revenues:	$	—		$	—
Less(1):
Research and development expenses(2):
Compensation and related expenses		21,828			24,537
Drug discovery and platform		1,026			844
Clinical and manufacturing activities		52,065			36,831
Occupancy and all other costs		7,461			8,037

Total research and development expense	$	82,380		$	70,249
General and administrative expenses(3):
Compensation and related expenses		8,174			7,912
Consulting and professional services		4,382			4,791
Occupancy and all other costs		1,800			1,243

Total general and administrative expense	$	14,356		$	13,946
Stock-based compensation		8,931			7,060
Other segment items(4)		(5,060	)		(8,146	)

Net loss	$	(100,607	)	$	(83,109	)

(1)	The significant expense categories and amounts align with the segment-level information that is regularly provided to the chief operating decision maker.

(2)	Research and development expense for the years ended December 31, 2025 and 2024 exclude $3.7 million and $2.9 million of stock-based compensation expense, respectively, which is presented separately below.

(3)	General & administrative expense for the years ended December 31, 2025 and 2024 exclude $5.2 million and $4.1 million of stock-based compensation expense, respectively, which is presented separately below.

(4)	Other segment items include interest and other income, net.

Lease - Summary of Measurement of Operating Leases (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024
Lease, Cost [Abstract]
Weighted-average remaining lease term (years)		1 year 10 months 24 days	2 years 9 months 18 days
Weighted-average discount rate		6.82%	7.13%
Cash paid for amounts included in the measurement of operating lease liabilities	$ 3,000	$ 2,896	$ 2,776

Segment Information

6 Months Ended

12 Months Ended

Jun. 30, 2026

Dec. 31, 2025

Segment Reporting [Abstract]

Segment Information

13. Segment Information

The Company’s Chief Executive Officer serves as the chief operating decision maker and reviews cash, cash equivalents and marketable securities as a measure of segment assets. As of June 30, 2026 and December 31, 2025, the Company’s cash, cash equivalents and marketable securities were $34.4 million and $80.5 million, respectively.

The following tables illustrate information about segment revenue, significant segment expenses and segment operating loss for the three and six months ended June 30, 2026 and 2025:


	Three Months Ended June 30,						Six Months Ended June 30,
	2026			2025			2026			2025
Revenues:	$	—		$	—		$	—		$	—
Less(1):
Research and development expenses(2):
Compensation and related expenses		5,486			7,067			10,734			13,156
Drug discovery and platform		51			417			249			567
Clinical and manufacturing activities		12,637			12,428			20,448			24,447
Occupancy and all other costs		2,687			1,872			4,482			3,915

Total research and development expense	$	20,861		$	21,784		$	35,913		$	42,085
General and administrative expenses(3):
Compensation and related expenses		2,096			2,228			4,359			4,576
Consulting and professional services		1,244			1,010			2,441			2,249
Occupancy and all other costs		387			475			701			1,081

Total general and administrative expense	$	3,727		$	3,713		$	7,501		$	7,906
Stock-based compensation		1,552			2,762			3,006			4,871
Other segment items(4)		(276	)		(1,363	)		(923	)		(2,980	)

Net loss	$	25,864		$	26,896		$	45,497		$	51,882

(1)	The significant expense categories and amounts align with the segment-level information that is regularly provided to the chief operating decision maker.

(2)

(3)

(4)	Other segment items include interest and other income, net.

14. Segment Information

The Company operates and manages its business as a single segment, focused on developing engineered cell and gene therapies to deliver transformative outcomes for patients. The Company’s cytoDRiVE

technology is designed to precisely regulate the timing and level of protein function by using

FDA-approved

small molecule drugs. The Company’s lead investigational cytoTIL15

™

program,

amsoki-cel,

is a novel engineered tumor-derived autologous T cell immunotherapy, with the potential to become a treatment option for metastatic melanoma and other solid tumors.

The determination of a single reporting and operating segment is consistent with the consolidated financial information regularly provided to the Company’s chief operating decision maker (“CODM”). The Company’s Chief Executive Officer (“CEO”), as the CODM, uses consolidated, single-segment financial information for purposes of evaluating performance, making operating decisions, allocating resources, and planning and forecasting for future periods. The CODM assesses performance and decides how to allocate resources based on consolidated net income (loss). This measure is used to monitor budget versus actual results to evaluate the performance of the segment. The CODM reviews cash, cash equivalents and marketable securities as a measure of segment assets. As of December 31, 2025 and 2024, the Company’s cash, cash equivalents and marketable securities were $80.5 million

and

$168.3 million,

respectively

The following tables illustrate information about segment revenue, significant segment expenses and segment operating loss for the years ended December 31, 2025 and 2024 (in thousands):


	Year Ended December 31,
	2025			2024
Revenues:	$	—		$	—
Less(1):
Research and development expenses(2):
Compensation and related expenses		21,828			24,537
Drug discovery and platform		1,026			844
Clinical and manufacturing activities		52,065			36,831
Occupancy and all other costs		7,461			8,037

Total research and development expense	$	82,380		$	70,249
General and administrative expenses(3):
Compensation and related expenses		8,174			7,912
Consulting and professional services		4,382			4,791
Occupancy and all other costs		1,800			1,243

Total general and administrative expense	$	14,356		$	13,946
Stock-based compensation		8,931			7,060
Other segment items(4)		(5,060	)		(8,146	)

Net loss	$	(100,607	)	$	(83,109	)

(1)	The significant expense categories and amounts align with the segment-level information that is regularly provided to the chief operating decision maker.

(2)	Research and development expense for the years ended December 31, 2025 and 2024 exclude $3.7 million and $2.9 million of stock-based compensation expense, respectively, which is presented separately below.

(3)	General & administrative expense for the years ended December 31, 2025 and 2024 exclude $5.2 million and $4.1 million of stock-based compensation expense, respectively, which is presented separately below.

(4)	Other segment items include interest and other income, net.

- Definition

The entire disclosure for segment reporting.

+ References

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+ Details