Commitments and Contingencies	6 Months Ended
Jun. 30, 2026
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Letter of Credit Restricted cash equivalents consist of $0.9 million of cash serving as collateral for a letter of credit issued for the Company’s office spaces, and $0.1 million as collateral for a corporate credit card program. As of June 30, 2026 and December 31, 2025, the Company’s restricted cash equivalents balance was $1.0 million on its condensed consolidated balance sheets. Legal Proceedings On February 9, 2024, a putative class action lawsuit was filed in the U.S. District Court for the Southern District of New York against us and certain of our current and former officers (Shih v. Amylyx Pharmaceuticals, Inc., et al., Case Number 1:24-CV-00988, or the Shih Complaint). Plaintiff filed an amended complaint on June 24, 2024. The Shih Complaint asserts a claim against all defendants for alleged violations of Section 10(b) of the Exchange Act and Rule 10b-5 promulgated thereunder and a claim under Section 20(a) against certain current and former officers as alleged controlling persons. The Shih Complaint alleges that defendants made materially false and misleading statements related to the commercial results and prospects for RELYVRIO. The Shih Complaint seeks unspecified damages, interest, costs and attorneys’ fees, and other unspecified relief that the court deems appropriate. On August 12, 2024, the case was transferred from the U.S. District Court for the Southern District of New York to the U.S. District Court for the District of Massachusetts, or the Court, and assigned docket number 1:24-CV-12068. Following the transfer, on September 6, 2024, defendants moved to dismiss the Shih Complaint. On September 30, 2025, the Court issued an order finding that the majority of the alleged misstatements are inactionable, but ultimately denied the motion to dismiss. The Company filed an answer on October 30, 2025. The parties have reached an agreement in principle to settle the class claims, subject to court approval, for $6.5 million, a significant portion of which was funded by insurance proceeds. On May 19, 2026, the court issued an order preliminarily approving the settlement and scheduled a final settlement approval hearing for September 10, 2026. In addition to the Shih Complaint, two derivative complaints were filed in the U.S. District Court for the District of Massachusetts on October 2, 2024, Jones v. Cohen, et al., 1:24-cv-12527, and on July 2, 2025, Hassine v. Cohen, et al., 1:25-CV-11879 (together, the Massachusetts Derivative Complaints) against certain current and former director and officer defendants (and naming the company as a nominal defendant). The substantive allegations in the Massachusetts Derivative Complaints mirror those of the Shih Complaint but assert claims for alleged violations of the Exchange Act, breach of fiduciary duty, insider trading, and unjust enrichment (among other common law claims) and seek unspecified damages to be awarded to the Company along with interest, restitution, unspecified corporate governance and internal procedural reforms and improvements, and plaintiff's attorneys' fees and costs. On July 16, 2025, the parties to both Massachusetts Derivative Complaints moved the Court to consolidate the two actions and stay the consolidated action, which the Court approved on July 22, 2025. On June 12, 2026, following the lifting of the stay, plaintiffs filed an amended complaint. On July 14, 2026, the parties filed a stipulation with the court informing it that they were engaged in the negotiation of as settlement term sheet and seeking an extension to existing deadlines to allow the parties to finalize the term sheet and negotiate a formal settlement agreement, which the court granted on July 15, 2026. In the event that a settlement cannot be reached, Defendants’ deadline to file a motion to dismiss the amended complaint is currently August 13, 2026. On April 7, 2026, a third derivative complaint was filed in Delaware Court of Chancery against certain current and former directors and officer defendants, naming the Company as nominal defendant, Schweitzer v. Klee, et al., 2026-0459-BWD (the Schweitzer Complaint and, together with the Massachusetts Derivative Complaints, the Derivative Complaints). Like the Massachusetts Complaints, the substantive allegations of the Schweitzer Complaint mirror those of the Shih Complaint and allege breach of fiduciary duty and other common law claims and seeks unspecified damages with interest, costs, and attorneys’ fees, restitution, and certain corporate governance and internal procedural reforms and improvements. The Schweitzer Complaint plaintiff is participating in the above-referenced settlement negotiations to attempt to resolve the Derivative Complaints. To the extent a resolution of the Derivative Complaints cannot be reached, we intend to defend against the Derivative Complaints vigorously. At this time, an estimate of the impact, if any, of the claims made in the Derivative Complaints cannot be made. Royalty Payments The Company has entered into a limited number of grant and royalty agreements that include payment obligations contingent upon future events, such as commercialization or the receipt of proceeds from revenue-generating transactions related to the underlying technologies. As the conditions that would trigger royalty payments have not been met, no amounts have been recorded in the consolidated financial statements. Purchase Commitments The Company enters into agreements in the normal course of business with contract manufacturing organizations, or CMOs, for raw material purchases and manufacturing services. As of June 30, 2026, the Company had approximately $35.0 million of remaining unconditional purchase obligations that are expected to be paid through 2028. Of this amount, approximately $13.6 million is expected to be paid within the next 12 months, and approximately $21.5 million is expected to be paid thereafter through 2028.

Commitments and Contingencies

6 Months Ended

Jun. 30, 2026

Commitments and Contingencies Disclosure [Abstract]

9. Commitments and Contingencies

Letter of Credit

Restricted cash equivalents consist of $0.9 million of cash serving as collateral for a letter of credit issued for the Company’s office spaces, and $0.1 million as collateral for a corporate credit card program. As of June 30, 2026 and December 31, 2025, the Company’s restricted cash equivalents balance was $1.0 million on its condensed consolidated balance sheets.

Legal Proceedings

On February 9, 2024, a putative class action lawsuit was filed in the U.S. District Court for the Southern District of New York against us and certain of our current and former officers (Shih v. Amylyx Pharmaceuticals, Inc., et al., Case Number 1:24-CV-00988, or the Shih Complaint). Plaintiff filed an amended complaint on June 24, 2024. The Shih Complaint asserts a claim against all defendants for alleged violations of Section 10(b) of the Exchange Act and Rule 10b-5 promulgated thereunder and a claim under Section 20(a) against certain current and former officers as alleged controlling persons. The Shih Complaint alleges that defendants made materially false and misleading statements related to the commercial results and prospects for RELYVRIO. The Shih Complaint seeks unspecified damages, interest, costs and attorneys’ fees, and other unspecified relief that the court deems appropriate. On August 12, 2024, the case was transferred from the U.S. District Court for the Southern District of New York to the U.S. District Court for the District of Massachusetts, or the Court, and assigned docket number 1:24-CV-12068. Following the transfer, on September 6, 2024, defendants moved to dismiss the Shih Complaint. On September 30, 2025, the Court issued an order finding that the majority of the alleged misstatements are inactionable, but ultimately denied the motion to dismiss. The Company filed an answer on October 30, 2025. The parties have reached an agreement in principle to settle the class claims, subject to court approval, for $6.5 million, a significant portion of which was funded by insurance proceeds. On May 19, 2026, the court issued an order preliminarily approving the settlement and scheduled a final settlement approval hearing for September 10, 2026.

In addition to the Shih Complaint, two derivative complaints were filed in the U.S. District Court for the District of Massachusetts on October 2, 2024, Jones v. Cohen, et al., 1:24-cv-12527, and on July 2, 2025, Hassine v. Cohen, et al., 1:25-CV-11879 (together, the Massachusetts Derivative Complaints) against certain current and former director and officer defendants (and naming the company as a nominal defendant). The substantive allegations in the Massachusetts Derivative Complaints mirror those of the Shih Complaint but assert claims for alleged violations of the Exchange Act, breach of fiduciary duty, insider trading, and unjust

enrichment (among other common law claims) and seek unspecified damages to be awarded to the Company along with interest, restitution, unspecified corporate governance and internal procedural reforms and improvements, and plaintiff's attorneys' fees and costs.

On July 16, 2025, the parties to both Massachusetts Derivative Complaints moved the Court to consolidate the two actions and stay the consolidated action, which the Court approved on July 22, 2025. On June 12, 2026, following the lifting of the stay, plaintiffs filed an amended complaint. On July 14, 2026, the parties filed a stipulation with the court informing it that they were engaged in the negotiation of as settlement term sheet and seeking an extension to existing deadlines to allow the parties to finalize the term sheet and negotiate a formal settlement agreement, which the court granted on July 15, 2026. In the event that a settlement cannot be reached, Defendants’ deadline to file a motion to dismiss the amended complaint is currently August 13, 2026.

On April 7, 2026, a third derivative complaint was filed in Delaware Court of Chancery against certain current and former directors and officer defendants, naming the Company as nominal defendant, Schweitzer v. Klee, et al., 2026-0459-BWD (the Schweitzer Complaint and, together with the Massachusetts Derivative Complaints, the Derivative Complaints). Like the Massachusetts Complaints, the substantive allegations of the Schweitzer Complaint mirror those of the Shih Complaint and allege breach of fiduciary duty and other common law claims and seeks unspecified damages with interest, costs, and attorneys’ fees, restitution, and certain corporate governance and internal procedural reforms and improvements. The Schweitzer Complaint plaintiff is participating in the above-referenced settlement negotiations to attempt to resolve the Derivative Complaints. To the extent a resolution of the Derivative Complaints cannot be reached, we intend to defend against the Derivative Complaints vigorously. At this time, an estimate of the impact, if any, of the claims made in the Derivative Complaints cannot be made.

Royalty Payments

The Company has entered into a limited number of grant and royalty agreements that include payment obligations contingent upon future events, such as commercialization or the receipt of proceeds from revenue-generating transactions related to the underlying technologies. As the conditions that would trigger royalty payments have not been met, no amounts have been recorded in the consolidated financial statements.

Purchase Commitments

The Company enters into agreements in the normal course of business with contract manufacturing organizations, or CMOs, for raw material purchases and manufacturing services. As of June 30, 2026, the Company had approximately $35.0 million of remaining unconditional purchase obligations that are expected to be paid through 2028. Of this amount, approximately $13.6 million is expected to be paid within the next 12 months, and approximately $21.5 million is expected to be paid thereafter through 2028.