Subsequent Events	3 Months Ended
Mar. 31, 2026
Subsequent Events [Abstract]
Subsequent Events	17. Subsequent Events. On May 6, 2026, the Company entered into an Agreement and Plan of Merger (the Merger Agreement) with Angelini Pharma S.p.A., an Italian Società per azioni (Angelini Pharma or Parent), and Angelini Cielo Inc., a Delaware corporation and wholly-owned subsidiary of Parent (Merger Sub), providing for the merger of Merger Sub with and into the Company (the Merger), with the Company surviving the Merger as a wholly-owned subsidiary of Parent. At the effective time of the Merger (the Effective Time), each share of the Company’s common stock, par value $0.001 per share (Shares), issued and outstanding immediately prior to the Effective Time (other than Shares held by the Company, Parent, and any of their respective subsidiaries, and Shares held by stockholders who have properly exercised and perfected appraisal rights and not withdrawn or waived such rights) will be canceled and converted into the right to receive $31.50 per Share in cash, without interest thereon (Merger Consideration) and subject to any applicable tax withholding. The Merger Agreement contains customary representations, warranties, and covenants, including covenants obligating the Company to use reasonable best efforts to conduct its business and operations in all material respects in the ordinary course of business consistent with past practice, to take all actions necessary or advisable to obtain required regulatory approvals, and not to engage in certain specified activities without Angelini Pharma's prior written consent. If the Merger Agreement is terminated under specified circumstances, the Company will be required to pay Parent a termination fee of approximately $155.5 million. The Company also expects to incur significant costs, expenses, and fees for professional services and other transaction costs in connection with the Merger. The foregoing description of the Merger Agreement does not purport to be complete and is subject to, and qualified in its entirety by, the full text of the Merger Agreement, a copy of which is attached as Exhibit 2.1 to the Company's Current Report on Form 8-K filed with the SEC on May 7, 2026. On May 7, 2026, the Company issued a press release announcing that it and its licensor, SERB, have entered into a settlement agreement (Settlement Agreement) with Hetero. This Settlement Agreement resolves the patent litigation brought by the Company and SERB in response to Hetero’s ANDA seeking approval to market a generic version of FIRDAPSE® (amifampridine) 10 mg tablets prior to expiration of the applicable patents. Pursuant to the terms of the Settlement Agreement, Hetero will not market its generic version of FIRDAPSE® in the United States any earlier than January 2035, if approved by the FDA, unless certain limited circumstances customarily included in these types of agreements occur. In accordance with the Settlement Agreement, the parties will terminate all ongoing patent litigation between the Company/SERB and Hetero regarding FIRDAPSE® patents pending in the U.S. District Court for the District of New Jersey. The Company previously settled similar litigation regarding ANDA applications for FIRDAPSE® with Teva, Inventia and Lupin. The Company also agreed to pay a litigation avoidance fee in the amount of $11.0 million to Hetero as part of the settlement. As required by law, the Company and Hetero will submit the Settlement Agreement to the U.S. Federal Trade Commission and the U.S. Department of Justice for review.

Subsequent Events

3 Months Ended

Mar. 31, 2026

17.

Subsequent Events.

On May 6, 2026, the Company entered into an Agreement and Plan of Merger (the Merger Agreement) with Angelini Pharma S.p.A., an Italian Società per azioni (Angelini Pharma or Parent), and Angelini Cielo Inc., a Delaware corporation and wholly-owned subsidiary of Parent (Merger Sub), providing for the merger of Merger Sub with and into the Company (the Merger), with the Company surviving the Merger as a wholly-owned subsidiary of Parent. At the effective time of the Merger (the Effective Time), each share of the Company’s common stock, par value $0.001 per share (Shares), issued and outstanding immediately prior to the Effective Time (other than Shares held by the Company, Parent, and any of their respective subsidiaries, and Shares held by stockholders who have properly exercised and perfected appraisal rights and not withdrawn or waived such rights) will be canceled and converted into the right to receive $31.50 per Share in cash, without interest thereon (Merger Consideration) and subject to any applicable tax withholding. The Merger Agreement contains customary representations, warranties, and covenants, including covenants obligating the Company to use reasonable best efforts to conduct its business and operations in all material respects in the ordinary course of business consistent with past practice, to take all actions necessary or advisable to obtain required regulatory approvals, and not to engage in certain specified activities without Angelini Pharma's prior written consent. If the Merger Agreement is terminated under specified circumstances, the Company will be required to pay Parent a termination fee of approximately $155.5 million. The Company also expects to incur significant costs, expenses, and fees for professional services and other transaction costs in connection with the Merger. The foregoing description of the Merger Agreement does not purport to be complete and is subject to, and qualified in its entirety by, the full text of the Merger Agreement, a copy of which is attached as Exhibit 2.1 to the Company's Current Report on Form 8-K filed with the SEC on May 7, 2026.

On May 7, 2026, the Company issued a press release announcing that it and its licensor, SERB, have entered into a settlement agreement (Settlement Agreement) with Hetero. This Settlement Agreement resolves the patent litigation brought by the Company and SERB in response to Hetero’s ANDA seeking approval to market a generic version of FIRDAPSE® (amifampridine) 10 mg tablets prior to expiration of the applicable patents. Pursuant to the terms of the Settlement Agreement, Hetero will not market its generic version of FIRDAPSE® in the United States any earlier than January 2035, if approved by the FDA, unless certain limited circumstances customarily included in these types of agreements occur. In accordance with the Settlement Agreement, the parties will terminate all ongoing patent litigation between the Company/SERB and Hetero regarding FIRDAPSE® patents pending in the U.S. District Court for the District of New Jersey. The Company previously settled similar litigation regarding ANDA applications for FIRDAPSE® with Teva, Inventia and Lupin. The Company also agreed to pay a litigation avoidance fee in the amount of $11.0 million to Hetero as part of the settlement. As required by law, the Company and Hetero will submit the Settlement Agreement to the U.S. Federal Trade Commission and the U.S. Department of Justice for review.