Significant accounting policies (Policies)	9 Months Ended
Sep. 30, 2026
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All inter-company balances and transactions have been eliminated. The unaudited condensed consolidated financial statements of the Company have been prepared in accordance with U.S. GAAP for interim financial statements. In the opinion of management, the Company has made all necessary adjustments, which include normal recurring adjustments necessary for a fair statement of the Company’s unaudited condensed consolidated financial position, results of operations, cash flow and statement of stockholders' equity for the interim periods presented. Certain information and disclosures normally included in the annual audited consolidated financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. Pre-Merger Yarrow was incorporated on October 3, 2025 and, accordingly, no comparative information is presented for the three and nine months ended September 30, 2025. For the three and nine months ended September 30, 2026, the Company had no components of other comprehensive income or loss from non-owner sources. Accordingly, a separate Statement of Comprehensive Income (Loss) has not been presented, and net loss equals total comprehensive loss for all periods presented. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and related notes for the year ended December 31, 2025 included in the Company’s Current Report on Form 8-K/A filed with the Securities and Exchange Commission (the “SEC”) on August 13, 2026. The results for the three and nine months ended September 30, 2026 are not necessarily indicative of the results expected for the year ending December 31, 2026.
Use of estimates	Use of estimates The preparation of unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the unaudited condensed consolidated financial statements and the reported amounts of income and expenses during the reporting period. Significant estimates and assumptions made in the accompanying financial statements include the accrual and prepayment of research and development expenses and the fair value of stock-based compensation and related assumptions. Actual results could differ from the Company’s estimates.
Cash and cash equivalents	Cash and cash equivalents The Company considers cash equivalents to be all short-term, highly liquid investments, which include short-term bank deposits, treasury bills and money market funds with original maturities of three months or less from the date of purchase that are not restricted as to withdrawal or use and are readily convertible to known amounts of cash.
Property and equipment	Property and equipment Property and equipment are stated at cost, net of accumulated depreciation. The Company’s property and equipment are depreciated by the straight-line method on the basis of their estimated useful life.
Deferred transaction costs	Deferred transaction costs Specific incremental legal, accounting and other fees and costs directly attributable to a proposed or actual offering of securities may properly be deferred and charged against the gross proceeds of such an offering. Upon the Closing of the Merger, the balance of the deferred transaction costs, up to the amount of cash acquired in the Merger, was reclassified to equity with the excess of $2.0 million expensed to general and administrative expenses. No other deferred transaction costs remained in other assets as of September 30, 2026.
Classification of convertible preferred stock	Classification of convertible preferred stock Prior to the reverse recapitalization, Pre-Merger Yarrow had classified the Pre-Merger Yarrow Series A Convertible Preferred Stock (the “Convertible Preferred Stock”) outside of stockholders’ deficit on the Company’s balance sheet because the holders of such stock had certain liquidation rights in the event of a Deemed Liquidation Event (as defined in Pre-Merger Yarrow's Amended and Restated Certificate of Incorporation) that, in certain situations, is not solely within the control of the Company and would require the redemption of the then-outstanding Convertible Preferred Stock. Upon the Closing of the Merger, the Company converted the Convertible Preferred Stock to common stock and pre-funded warrants within stockholders’ equity (deficit) on its condensed consolidated balance sheet.
Warrants	Warrants The Company accounts for warrants as either equity-classified or liability-classified instruments based on an assessment of the warrant’s specific terms and applicable authoritative guidance in ASC Topic 480, Distinguishing Liabilities from Equity (“ASC 480”) and ASC Topic 815, Derivatives and Hedging (“ASC 815”). The assessment considers whether the warrants are freestanding financial instruments pursuant to ASC 480, meet the definition of a liability pursuant to ASC 480, and meet all of the requirements for equity classification under ASC 815, including whether the warrants are indexed to the Company’s own common stock, among other conditions for equity classification. This assessment, which requires the use of professional judgment, is conducted at the time of warrant issuance and as of each subsequent reporting period end date while the warrants are outstanding. For issued warrants that meet all of the criteria for equity classification, the warrants are required to be recorded as a component of additional paid-in capital at the time of issuance. For issued warrants that do not meet all the criteria for equity classification, the warrants are required to be recorded at their initial fair value on the date of issuance and at each balance sheet date thereafter. Changes in the estimated fair value of the warrants are recognized as a non-cash gain or loss on the statements of operations. As of September 30, 2026, all of the Company's outstanding warrants were equity-classified warrants.
Stock-based compensation expense	Stock-based compensation expense The Company measures stock-based awards, including stock options, at their grant-date fair value and records compensation expense over the requisite service period, which is the vesting period of the awards. The Company accounts for forfeitures as they occur. Estimating the fair value of stock options requires the use of subjective assumptions, including the fair value of the Company’s common stock, the expected term of the option and expected stock price volatility. The Company uses the Black-Scholes option-pricing model to value its stock option awards. The assumptions used in calculating the fair value of stock options represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment. As a result, if factors change and management uses different assumptions, stock-based compensation expense could be materially different for future awards. Prior to the Merger, the fair value of the Company’s common stock was estimated by the Company’s board of directors, with input from management considering the most recently available third-party valuation of the Company’s common stock. Following the Merger, the fair value of the Company’s common stock is based on the closing price of the common stock on The Nasdaq Capital Market on the date of grant. The expected term of stock options for employees is estimated using the “simplified method,” as the Company has limited historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior for its stock option grants. The simplified method is the midpoint between the vesting date and the contractual term of the option. The contractual term is used as the expected term for stock options granted to non-employees. For stock price volatility, the Company uses comparable public companies as a basis for the expected volatility to calculate the fair value of option grants. The risk-free rate is based on the U.S. Treasury yield curve commensurate with the expected term of the option. The expected dividend yield is zero given the Company does not expect to pay dividends for the foreseeable future.
Research and development expenses	Research and development expenses All expenses associated with research and development are expensed as incurred. Research and development expenses include expenses directly attributable to conducting the Company’s research and development programs, including expenses incurred under arrangements with third parties, such as contract research organizations, contract development and manufacturing organizations and consultants as well as the cost of clinical trials, clinical trial supplies, salaries, stock-based compensation expenses, payroll taxes and other employee benefits. Expenses are considered incurred based on the evaluation of the progress to completion of specific tasks under each contract using information and data provided by the service providers and vendors or the Company’s estimate of the level of service that has been performed at each reporting date, whereas payments are dictated by the terms of each agreement, such as the successful enrollment of a certain number of patients, site initiation, and the completion of clinical trial milestones. As such, depending on the timing of payment relative to the receipt of goods or services, management may record prepaid expenses, accrued expenses, or other assets.
Fair value measurement	Fair value measurement Fair value is based on the price that would be received from the sale of an asset or that would be paid to transfer a liability in an orderly transaction between market participants at the measurement date. In order to increase consistency and comparability in fair value measurements, the guidance establishes a fair value hierarchy that prioritizes observable and unobservable inputs used to measure fair value into three broad levels, which are described as follows: Level 1: Quoted prices (unadjusted) in active markets that are accessible at the measurement date for assets or liabilities. The fair value hierarchy gives the highest priority to Level 1 inputs. Level 2: Observable prices that are based on inputs not quoted on active markets but corroborated by market data or active market data of similar or identical assets or liabilities. Level 3: Unobservable inputs are used when little or no market data is available. The fair value hierarchy gives the lowest priority to Level 3 inputs. In determining fair value, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible and considers counterparty credit risk in its assessment of fair value.
Income taxes	Income taxes Deferred taxes Income taxes are computed using the asset and liability method. Under the asset and liability method, deferred income tax assets and liabilities are determined based on the differences between the financial reporting and tax bases of assets and liabilities and are measured using the currently enacted tax rates and laws. A valuation allowance is recognized to the extent that it is more likely than not that the deferred taxes will not be realized in the foreseeable future. Given the Company’s losses, the Company has provided a full valuation allowance with respect to its deferred tax assets. Uncertainty in income tax The Company follows a two-step approach in recognizing and measuring uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the available evidence indicates that it is more likely than not that the position will be sustained based on technical merits. If this threshold is met, the second step is to measure the tax position as the largest amount that has more than a 50% likelihood of being realized upon ultimate settlement. The Company has not completed a Section 382 study through September 30, 2026; however, the Company may have experienced ownership changes in connection with the Merger and the September 2026 Offering. One Big Beautiful Bill Act On July 4, 2025, President Trump signed into law the One Big Beautiful Bill Act, which made comprehensive revisions to federal corporate income tax provisions, including those related to research and development expense treatment, full expensing of business assets, interest deduction limitations, and international tax regimes such as global intangible low-taxed income, foreign-derived intangible income, and controlled foreign corporation look-through rules. The enactment of this legislation did not have a material impact on the Company’s income tax provision for the three and nine months ended September 30, 2026.
Net loss per share	Net loss per share Net loss per share, basic and diluted, is computed on the basis of the net loss from operations for the period divided by the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share is based upon the weighted average number of shares of common stock and of common stock equivalents outstanding when dilutive. The Company has issued pre-funded warrants to purchase the Company’s common stock, which do not expire until they are exercised in full (see "Note 8 - Stockholders' equity"). Pursuant to the guidance of ASC 260-10, the Company concluded that because the equity-classified pre-funded warrants were immediately exercisable for little or no cash consideration, due to the non-substantive exercise price, all of the necessary conditions for issuance of the underlying shares of common stock had been met when the pre-funded warrants were issued. Therefore, the underlying shares of common stock should be included in the denominator for both the calculation of basic and diluted net loss per share of common stock for the three and nine months ended September 30, 2026.
Concentration of credit risks	Concentration of credit risks Financial instruments that potentially subject the Company to concentration of credit risk consist principally of cash and cash equivalents. The Company deposits cash and cash equivalents with highly rated financial institutions and, as a matter of policy, limits the amounts of credit exposure to any single financial institution. The Company has not experienced any material credit losses in these accounts and does not believe it is exposed to significant credit risk on these instruments.
Newly issued and recently adopted accounting pronouncements	Newly issued and recently adopted accounting pronouncements Recently issued accounting pronouncements: In November 2024, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2024-03, “Comprehensive Income (Topic 220)—Disaggregation of Income Statement Expenses” (“ASU 2024-03”), to improve financial reporting by requiring disclosures in the notes to financial statements about specific types of expenses included in the expense captions presented on the face of the statement of operations and comprehensive loss. The requirements of the ASU, as clarified by ASU 2025-01 issued in January 2025, are effective for annual reporting periods beginning after December 15, 2026 and for interim reporting periods beginning after December 15, 2027, with early adoption permitted. The requirements will be applied prospectively with the option for retrospective application. The Company is evaluating the impact the adoption of this guidance will have on its unaudited condensed consolidated financial statements and related disclosures.

Significant accounting policies (Policies)

9 Months Ended

Sep. 30, 2026

The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All inter-company balances and transactions have been eliminated.

The unaudited condensed consolidated financial statements of the Company have been prepared in accordance with U.S. GAAP for interim financial statements. In the opinion of management, the Company has made all necessary adjustments, which include normal recurring adjustments necessary for a fair statement of the Company’s unaudited condensed consolidated financial position, results of operations, cash flow and statement of stockholders' equity for the interim periods presented. Certain information and disclosures normally included in the annual audited consolidated financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. Pre-Merger Yarrow was incorporated on October 3, 2025 and, accordingly, no comparative information is presented for the three and nine months ended September 30, 2025.

For the three and nine months ended September 30, 2026, the Company had no components of other comprehensive income or loss from non-owner sources. Accordingly, a separate Statement of Comprehensive Income (Loss) has not been presented, and net loss equals total comprehensive loss for all periods presented.

These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and related notes for the year ended December 31, 2025 included in the Company’s Current Report on Form 8-K/A filed with the Securities and Exchange Commission (the “SEC”) on August 13, 2026.

The results for the three and nine months ended September 30, 2026 are not necessarily indicative of the results expected for the year ending December 31, 2026.

Use of estimates

The preparation of unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the unaudited condensed consolidated financial statements and the reported amounts of income and expenses during the reporting period. Significant estimates and assumptions made in the accompanying financial statements include the accrual and prepayment of research and development expenses and the fair value of stock-based compensation and related assumptions. Actual results could differ from the Company’s estimates.

Cash and cash equivalents

The Company considers cash equivalents to be all short-term, highly liquid investments, which include short-term bank deposits, treasury bills and money market funds with original maturities of three months or less from the date of purchase that are not restricted as to withdrawal or use and are readily convertible to known amounts of cash.

Property and equipment

Property and equipment are stated at cost, net of accumulated depreciation. The Company’s property and equipment are depreciated by the straight-line method on the basis of their estimated useful life.

Deferred transaction costs

Specific incremental legal, accounting and other fees and costs directly attributable to a proposed or actual offering of securities may properly be deferred and charged against the gross proceeds of such an offering. Upon the Closing of the Merger, the balance of the deferred transaction costs, up to the amount of cash acquired in the Merger, was reclassified to equity with the

excess of $2.0 million expensed to general and administrative expenses. No other deferred transaction costs remained in other assets as of September 30, 2026.

Classification of convertible preferred stock

Prior to the reverse recapitalization, Pre-Merger Yarrow had classified the Pre-Merger Yarrow Series A Convertible Preferred Stock (the “Convertible Preferred Stock”) outside of stockholders’ deficit on the Company’s balance sheet because the holders of such stock had certain liquidation rights in the event of a Deemed Liquidation Event (as defined in Pre-Merger Yarrow's Amended and Restated Certificate of Incorporation) that, in certain situations, is not solely within the control of the Company and would require the redemption of the then-outstanding Convertible Preferred Stock.

Upon the Closing of the Merger, the Company converted the Convertible Preferred Stock to common stock and pre-funded warrants within stockholders’ equity (deficit) on its condensed consolidated balance sheet.

Warrants

The Company accounts for warrants as either equity-classified or liability-classified instruments based on an assessment of the warrant’s specific terms and applicable authoritative guidance in ASC Topic 480, Distinguishing Liabilities from Equity (“ASC 480”) and ASC Topic 815, Derivatives and Hedging (“ASC 815”). The assessment considers whether the warrants are freestanding financial instruments pursuant to ASC 480, meet the definition of a liability pursuant to ASC 480, and meet all of the requirements for equity classification under ASC 815, including whether the warrants are indexed to the Company’s own common stock, among other conditions for equity classification. This assessment, which requires the use of professional judgment, is conducted at the time of warrant issuance and as of each subsequent reporting period end date while the warrants are outstanding. For issued warrants that meet all of the criteria for equity classification, the warrants are required to be recorded as a component of additional paid-in capital at the time of issuance. For issued warrants that do not meet all the criteria for equity classification, the warrants are required to be recorded at their initial fair value on the date of issuance and at each balance sheet date thereafter. Changes in the estimated fair value of the warrants are recognized as a non-cash gain or loss on the statements of operations. As of September 30, 2026, all of the Company's outstanding warrants were equity-classified warrants.

Stock-based compensation expense

The Company measures stock-based awards, including stock options, at their grant-date fair value and records compensation expense over the requisite service period, which is the vesting period of the awards. The Company accounts for forfeitures as they occur.

Estimating the fair value of stock options requires the use of subjective assumptions, including the fair value of the Company’s common stock, the expected term of the option and expected stock price volatility. The Company uses the Black-Scholes option-pricing model to value its stock option awards. The assumptions used in calculating the fair value of stock options represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment. As a result, if factors change and management uses different assumptions, stock-based compensation expense could be materially different for future awards.

Prior to the Merger, the fair value of the Company’s common stock was estimated by the Company’s board of directors, with input from management considering the most recently available third-party valuation of the Company’s common stock. Following the Merger, the fair value of the Company’s common stock is based on the closing price of the common stock on The Nasdaq Capital Market on the date of grant. The expected term of stock options for employees is estimated using the “simplified method,” as the Company has limited historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior for its stock option grants. The simplified method is the midpoint between the vesting date and the contractual term of the option. The contractual term is used as the expected term for stock options granted to non-employees. For stock price volatility, the Company uses comparable public companies as a basis for the expected volatility to calculate the fair value of option grants. The risk-free rate is based on the U.S. Treasury yield curve commensurate with the expected term of the option. The expected dividend yield is zero given the Company does not expect to pay dividends for the foreseeable future.

Research and development expenses

All expenses associated with research and development are expensed as incurred. Research and development expenses include expenses directly attributable to conducting the Company’s research and development programs, including expenses incurred under arrangements with third parties, such as contract research organizations, contract development and manufacturing organizations and consultants as well as the cost of clinical trials, clinical trial supplies, salaries, stock-based compensation expenses, payroll taxes and other employee benefits.

Expenses are considered incurred based on the evaluation of the progress to completion of specific tasks under each contract using information and data provided by the service providers and vendors or the Company’s estimate of the level of service that has been performed at each reporting date, whereas payments are dictated by the terms of each agreement, such as the successful enrollment of a certain number of patients, site initiation, and the completion of clinical trial milestones. As such, depending on the timing of payment relative to the receipt of goods or services, management may record prepaid expenses, accrued expenses, or other assets.

Fair value measurement

Fair value is based on the price that would be received from the sale of an asset or that would be paid to transfer a liability in an orderly transaction between market participants at the measurement date. In order to increase consistency and comparability in fair value measurements, the guidance establishes a fair value hierarchy that prioritizes observable and unobservable inputs used to measure fair value into three broad levels, which are described as follows:

Level 1: Quoted prices (unadjusted) in active markets that are accessible at the measurement date for assets or liabilities. The fair value hierarchy gives the highest priority to Level 1 inputs.

Level 2: Observable prices that are based on inputs not quoted on active markets but corroborated by market data or active market data of similar or identical assets or liabilities.

Level 3: Unobservable inputs are used when little or no market data is available. The fair value hierarchy gives the lowest priority to Level 3 inputs.

In determining fair value, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible and considers counterparty credit risk in its assessment of fair value.

Income taxes

Deferred taxes

Income taxes are computed using the asset and liability method. Under the asset and liability method, deferred income tax assets and liabilities are determined based on the differences between the financial reporting and tax bases of assets and liabilities and are measured using the currently enacted tax rates and laws. A valuation allowance is recognized to the extent that it is more likely than not that the deferred taxes will not be realized in the foreseeable future. Given the Company’s losses, the Company has provided a full valuation allowance with respect to its deferred tax assets.

Uncertainty in income tax

The Company follows a two-step approach in recognizing and measuring uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the available evidence indicates that it is more likely than not that the position will be sustained based on technical merits. If this threshold is met, the second step is to measure the tax position as the largest amount that has more than a 50% likelihood of being realized upon ultimate settlement.

The Company has not completed a Section 382 study through September 30, 2026; however, the Company may have experienced ownership changes in connection with the Merger and the September 2026 Offering.

One Big Beautiful Bill Act

On July 4, 2025, President Trump signed into law the One Big Beautiful Bill Act, which made comprehensive revisions to federal corporate income tax provisions, including those related to research and development expense treatment, full expensing of business assets, interest deduction limitations, and international tax regimes such as global intangible low-taxed income, foreign-derived intangible income, and controlled foreign corporation look-through rules. The enactment of this legislation did not have a material impact on the Company’s income tax provision for the three and nine months ended September 30, 2026.

Net loss per share

Net loss per share, basic and diluted, is computed on the basis of the net loss from operations for the period divided by the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share is based upon the weighted average number of shares of common stock and of common stock equivalents outstanding when dilutive. The Company has issued pre-funded warrants to purchase the Company’s common stock, which do not expire until they are exercised in full (see "Note 8 - Stockholders' equity"). Pursuant to the guidance of ASC 260-10, the Company concluded that because the equity-classified pre-funded warrants were immediately exercisable for little or no cash consideration, due to the non-substantive exercise price, all of the necessary conditions for issuance of the underlying shares of common stock had been met when the pre-funded warrants were issued. Therefore, the underlying shares of common stock should be included in the denominator for both the calculation of basic and diluted net loss per share of common stock for the three and nine months ended September 30, 2026.

Concentration of credit risks

Financial instruments that potentially subject the Company to concentration of credit risk consist principally of cash and cash equivalents. The Company deposits cash and cash equivalents with highly rated financial institutions and, as a matter of policy, limits the amounts of credit exposure to any single financial institution. The Company has not experienced any material credit losses in these accounts and does not believe it is exposed to significant credit risk on these instruments.

Newly issued and recently adopted accounting pronouncements

Recently issued accounting pronouncements:

In November 2024, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2024-03, “Comprehensive Income (Topic 220)—Disaggregation of Income Statement Expenses” (“ASU 2024-03”), to improve financial reporting by requiring disclosures in the notes to financial statements about specific types of expenses included in the expense captions presented on the face of the statement of operations and comprehensive loss. The requirements of the ASU, as clarified by ASU 2025-01 issued in January 2025, are effective for annual reporting periods beginning after December 15, 2026 and for interim reporting periods beginning after December 15, 2027, with early adoption permitted. The requirements will be applied prospectively with the option for retrospective application. The Company is evaluating the impact the adoption of this guidance will have on its unaudited condensed consolidated financial statements and related disclosures.