10. Stock Option and Grant PlanS

Stock Incentive Plan—In January 2022, the Company’s board of directors adopted, and its stockholders approved the 2022 Stock Option and Incentive Plan, or 2022 Plan. Under the 2022 Plan, the Company may grant incentive stock options, or ISOs, non-statutory stock options, stock appreciation rights, restricted stock units, restricted stock awards and other stock-based awards. As of December 31, 2025, there were 4,815,653 shares available for future issuance under the 2022 Plan. The options issued under the 2022 Plan expire 10 years following the date of grant. Stock options and restricted stock units typically vest over 4 years. We recognize the compensation cost of awards subject to service-based vesting conditions over the requisite service period, which is generally equal to the vesting period of the respective award.

Initially, subject to adjustment as provided in the 2022 Plan, the aggregate number of shares of the Company’s common stock available for issuance under the 2022 Plan is 7,650,000. The number of shares of the Company’s common stock reserved for issuance under the 2022 Plan will automatically increase on January 1 of each year commencing January 1, 2023, by 5% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Company’s board of directors.

Inducement Plan—In July 2023, the Company’s board of directors adopted the Amylyx Pharmaceuticals, Inc. 2023 Inducement Plan, or the Inducement Plan, to grant equity awards to induce highly-qualified prospective officers and employees who are not currently employed by the Company to accept employment and provide them with a proprietary interest in the Company. The Company has reserved 750,000 shares of its common stock that may be issued under the Inducement Plan. As of December 31, 2025, there were 360,167 shares available for future issuance under the Inducement Plan.

Employee Stock Purchase Plan—In January 2022, the Company’s board of directors adopted the 2022 Employee Stock Purchase Plan, or ESPP, which was subsequently approved by the Company's stockholders. The ESPP initially reserves and authorizes the issuance of up to a total of 605,000 shares of common stock to participating employees. The ESPP provides that the number of shares reserved and available for issuance will automatically increase each January 1, beginning on January 1, 2023 and each January 1 thereafter through January 1, 2032, by the least of (i) 1% of the outstanding number of shares of our common stock on the immediately preceding December 31, (ii) 1,210,000 shares or (iii) such number of shares of common stock as determined by the ESPP administrator. The initial purchase period under the ESPP has not yet commenced. As of December 31, 2025, there were 2,633,491 shares available for future issuance under the ESPP.

The weighted average grant date fair value of stock options granted during the year ended December 31, 2025 and 2024 was $3.46 per share and $5.61 per share, respectively.

The aggregate intrinsic value of options exercised during the years ended December 31, 2025 and 2024 was $1.8 million and $1.0 million, respectively.

The total fair value of stock options vested during the years ended December 31, 2025 and 2024 was $18.5 million and $32.5 million, respectively.

Restricted Stock Unit Activity

Performance-Based Restricted Stock Unit Activity

In 2025, the Company granted performance-based restricted stock units, or PSUs, whereby vesting depends upon the occurrence of certain milestone events, or the 2025 PSUs. When achievement of milestone events, which include certain clinical milestones related to PBH, becomes probable, compensation cost will be recognized from the grant date over the requisite service period and a cumulative catch-up adjustment will be recorded to reflect the portion of the employees' requisite service that has been provided to date. As of December 31, 2025, none of the milestone events related to the 2025 PSUs had been deemed probable of being achieved.

Stock-Based Compensation Expense—The Company recorded stock-based compensation expense in the following expense categories of its statements of operations: