Summary of Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2025
Accounting Policies [Abstract]
Unaudited Interim Condensed Consolidated Financial Information	Unaudited Interim Condensed Consolidated Financial Information The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with GAAP for interim financial information. The accompanying unaudited condensed consolidated financial statements do not include all of the information and footnotes required by GAAP for complete consolidated financial statements. The accompanying year-end condensed consolidated balance sheet was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position, results of operations, and cash flows for all periods presented. The results for the three and nine months ended September 30, 2025 are not necessarily indicative of results to be expected for the year ending December 31, 2025, any other interim periods or any future year or period. The financial information included herein should be read in conjunction with the financial statements and notes in the Company's Annual Report on Form 10-K for the year ended December 31, 2024.
Reclassifications	Reclassifications Certain items in the prior period’s condensed consolidated financial statements have been reclassified to conform to the current year presentation.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with 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 condensed consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual for research and development expenses, valuation of forward contract and derivative liability, and valuation of notes payable. In addition, management’s assessment of the Company’s ability to continue as a going concern involves the estimation of the amount and timing of future cash inflows and outflows. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.
Restricted Cash	Restricted Cash Restricted cash included in other current assets in the condensed consolidated balance sheets consists primarily of employee contributions to the Company's employee share purchase plan held for future purchases of the Company's outstanding shares. See Note 8, "Non-Cash Share-Based Compensation," of the 2024 Form 10-K for additional information on the Company's employee share purchase plan. Restricted cash included in other non-current assets in the condensed consolidated balance sheets primarily represents collateral held by banks for a letter of credit ("LOC") issued in connection with the leased office space in Yardley, Pennsylvania and LOCs issued in connection with the leased office and lab spaces in Cambridge, Massachusetts and Pittsburgh, Pennsylvania. See Note 11, ‘‘Commitments and Contingencies,’’ of the 2024 Form 10-K for additional information on the real estate leases.
Valuation of Note Purchase Agreement	Valuation of Note Purchase Agreement On April 28, 2025 the Company entered into a Note Purchase Agreement (the “Note Purchase Agreement” or "NPA") with Beetlejuice SA LLC, an affiliate of Oberland Capital Management LLC ("Oberland"), certain subsidiaries of the Company, as obligors and the purchasers party thereto (the "Purchasers"), as described in further detail in Note 6, "Notes Payable." In addition to secured notes in the principal amount of $250,000, which were issued in April 2025, Oberland has agreed to purchase, at the option of the Company and subject to the satisfaction of certain conditions, including the receipt of approval from the U.S. Food and Drug Administration (the “FDA”) for troriluzole, a second tranche of secured notes in up to three purchases on or before June 30, 2026 for an aggregate purchase price of $150,000. The Company may also sell, at its option and subject to the approval of each Purchaser agreeing to participate therein, in its sole discretion, additional secured notes in up to four purchases for an aggregate purchase price of $200,000, the proceeds of which may be used solely to fund permitted acquisitions and related costs and expenses. Under the NPA, the Company will be obligated to make Revenue Payments (as defined in Note 6) based on a percentage of global net sales of troriluzole and make a Milestone Payment (as defined in Note 6), equal to 35% of the total funded amount, upon regulatory approval of any drug candidate. The Company assessed the terms and features of the NPA and determined that the Company is eligible to elect the fair value option under ASC 825, "Financial Instruments." The NPA contains various embedded features and the election of the fair value option allows the Company to bypass analysis of potential embedded derivatives and further analysis of bifurcation of any recognized financial liabilities. Under the fair value option, the financial liability, which is recorded as Notes Payable on the condensed consolidated balance sheet, is initially measured at its fair value on the issuance date and subsequently remeasured at estimated fair value on a recurring basis at each reporting date. Subsequent changes in fair value, excluding the impact of the change in fair value attributable to instrument-specific credit risk, are separately presented as a component of other income (expense), net in the condensed consolidated statements of operations and comprehensive loss. The portion of the fair value adjustment attributed to a change in the instrument-specific credit risk is recognized and separately presented as a component of other comprehensive income (loss). The portion of total changes in fair value attributable to changes in instrument-specific credit risk are determined through specific measurement of periodic changes in the discount rate assumption exclusive of base market changes and are presented as a component of comprehensive income (loss) in the accompanying condensed consolidated statements of operations and comprehensive loss. As the Company elected to account for the NPA under the fair value option, debt issuance costs, which were not material, were immediately expensed within general and administrative expense in the condensed consolidated statements of operations and comprehensive loss. Additionally, the Company has elected not to present interest expense separately from changes in fair value and therefore will not separately present interest expense associated with the NPA. The fair value of the NPA represents the present value of estimated future payments under the NPA. The fair value of the NPA is based on the cumulative probability of the various estimated payments. The fair value measurement is based on significant Level 3 unobservable inputs such as management's assumptions on the probability and timing of regulatory approvals for troriluzole and other product candidates, forecasted future revenue for troriluzole, probability and timing of an early redemption of all obligations under the NPA, and discount rate.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, to improve the transparency of income tax disclosures by requiring consistent categories and greater disaggregation of information in the rate reconciliation and income taxes paid disaggregated by jurisdiction. The ASU also includes certain other amendments to improve the effectiveness of income tax disclosures. ASU 2023-09 is effective for the Company for the fiscal year ending December 31, 2025. The Company does not plan to early adopt and is currently evaluating the impact ASU No. 2023-09 will have on its consolidated financial statements. In November 2024, the FASB issued ASU No. 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40), which requires disclosure, in the notes to the financial statements, of specified information about certain costs and expenses. This ASU is effective for public entities for annual reporting periods beginning after December 15, 2026 and interim reporting periods beginning after December 15, 2027. The Company is currently evaluating the impact ASU 2024-03 will have on its consolidated financial statements.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2025

Unaudited Interim Condensed Consolidated Financial Information

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with GAAP for interim financial information. The accompanying unaudited condensed consolidated financial statements do not include all of the information and footnotes required by GAAP for complete consolidated financial statements. The accompanying year-end condensed consolidated balance sheet was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position, results of operations, and cash flows for all periods presented. The results for the three and nine months ended September 30, 2025 are not necessarily indicative of results to be expected for the year ending December 31, 2025, any other interim periods or any future year or period. The financial information included herein should be read in conjunction with the financial statements and notes in the Company's Annual Report on Form 10-K for the year ended December 31, 2024.

Reclassifications

Certain items in the prior period’s condensed consolidated financial statements have been reclassified to conform to the current year presentation.

Use of Estimates

The preparation of condensed consolidated financial statements in conformity with 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 condensed consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual for research and development expenses, valuation of forward contract and derivative liability, and valuation of notes payable. In addition, management’s assessment of the Company’s ability to continue as a going concern involves the estimation of the amount and timing of future cash inflows and outflows. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.

Restricted Cash

Restricted cash included in other current assets in the condensed consolidated balance sheets consists primarily of employee contributions to the Company's employee share purchase plan held for future purchases of the Company's outstanding shares. See Note 8, "Non-Cash Share-Based Compensation," of the 2024 Form 10-K for additional information on the Company's employee share purchase plan.

Restricted cash included in other non-current assets in the condensed consolidated balance sheets primarily represents collateral held by banks for a letter of credit ("LOC") issued in connection with the leased office space in Yardley, Pennsylvania and LOCs issued in connection with the leased office and lab spaces in Cambridge, Massachusetts

and Pittsburgh, Pennsylvania. See Note 11, ‘‘Commitments and Contingencies,’’ of the 2024 Form 10-K for additional information on the real estate leases.

Valuation of Note Purchase Agreement

On April 28, 2025 the Company entered into a Note Purchase Agreement (the “Note Purchase Agreement” or "NPA") with Beetlejuice SA LLC, an affiliate of Oberland Capital Management LLC ("Oberland"), certain subsidiaries of the Company, as obligors and the purchasers party thereto (the "Purchasers"), as described in further detail in Note 6, "Notes Payable." In addition to secured notes in the principal amount of $250,000, which were issued in April 2025, Oberland has agreed to purchase, at the option of the Company and subject to the satisfaction of certain conditions, including the receipt of approval from the U.S. Food and Drug Administration (the “FDA”) for troriluzole, a second tranche of secured notes in up to three purchases on or before June 30, 2026 for an aggregate purchase price of $150,000. The Company may also sell, at its option and subject to the approval of each Purchaser agreeing to participate therein, in its sole discretion, additional secured notes in up to four purchases for an aggregate purchase price of $200,000, the proceeds of which may be used solely to fund permitted acquisitions and related costs and expenses. Under the NPA, the Company will be obligated to make Revenue Payments (as defined in Note 6) based on a percentage of global net sales of troriluzole and make a Milestone Payment (as defined in Note 6), equal to 35% of the total funded amount, upon regulatory approval of any drug candidate.

The Company assessed the terms and features of the NPA and determined that the Company is eligible to elect the fair value option under ASC 825, "Financial Instruments." The NPA contains various embedded features and the election of the fair value option allows the Company to bypass analysis of potential embedded derivatives and further analysis of bifurcation of any recognized financial liabilities.

Under the fair value option, the financial liability, which is recorded as Notes Payable on the condensed consolidated balance sheet, is initially measured at its fair value on the issuance date and subsequently remeasured at estimated fair value on a recurring basis at each reporting date. Subsequent changes in fair value, excluding the impact of the change in fair value attributable to instrument-specific credit risk, are separately presented as a component of other income (expense), net in the condensed consolidated statements of operations and comprehensive loss. The portion of the fair value adjustment attributed to a change in the instrument-specific credit risk is recognized and separately presented as a component of other comprehensive income (loss). The portion of total changes in fair value attributable to changes in instrument-specific credit risk are determined through specific measurement of periodic changes in the discount rate assumption exclusive of base market changes and are presented as a component of comprehensive income (loss) in the accompanying condensed consolidated statements of operations and comprehensive loss.

As the Company elected to account for the NPA under the fair value option, debt issuance costs, which were not material, were immediately expensed within general and administrative expense in the condensed consolidated statements of operations and comprehensive loss. Additionally, the Company has elected not to present interest expense separately from changes in fair value and therefore will not separately present interest expense associated with the NPA.

The fair value of the NPA represents the present value of estimated future payments under the NPA. The fair value of the NPA is based on the cumulative probability of the various estimated payments. The fair value measurement is based on significant Level 3 unobservable inputs such as management's assumptions on the probability and timing of

regulatory approvals for troriluzole and other product candidates, forecasted future revenue for troriluzole, probability and timing of an early redemption of all obligations under the NPA, and discount rate.

Recently Issued Accounting Pronouncements

In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, to improve the transparency of income tax disclosures by requiring consistent categories and greater disaggregation of information in the rate reconciliation and income taxes paid disaggregated by jurisdiction. The ASU also includes certain other amendments to improve the effectiveness of income tax disclosures. ASU 2023-09 is effective for the Company for the fiscal year ending December 31, 2025. The Company does not plan to early adopt and is currently evaluating the impact ASU No. 2023-09 will have on its consolidated financial statements.

In November 2024, the FASB issued ASU No. 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40), which requires disclosure, in the notes to the financial statements, of specified information about certain costs and expenses. This ASU is effective for public entities for annual reporting periods beginning after December 15, 2026 and interim reporting periods beginning after December 15, 2027. The Company is currently evaluating the impact ASU 2024-03 will have on its consolidated financial statements.