Amylyx Pharmaceuticals, Inc.

(a)

None.

(b)

Rule 10b5-1 Trading Arrangements

During the three months ended December 31, 2025, no officers or directors of the Company (as defined in Rule 16a-1(f))adopted, modified orterminated a “Rule 10b5-1 trading arrangement” or a “non-Rule 10b5-1 trading arrangement,” as each term is defined in Item 408(c) of Regulation S-K of the Exchange Act, except as described below:

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Joshua Cohen, our Co-Chief Executive Officer and a member of our board of directors, adopted a new "non-Rule 10b5-1 trading arrangement" on November 12, 2025, which is scheduled to expire on February 19, 2026. The aggregate number of shares of our common stock authorized to be sold under this new arrangement is 200,000. This trading plan covers the exercise and sale of stock options, with such sales limited to an amount reasonably estimated such that the net proceeds from the sale are sufficient to cover the exercise cost and taxes associated with the exercise of the stock options.

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Justin Klee, our Co-Chief Executive Officer and a member of our board of directors, adopted a new "non-Rule 10b5-1 trading arrangement" on November 12, 2025, which is scheduled to expire on February 19, 2026. The aggregate number of shares of our common stock authorized to be sold under this new arrangement is 200,000. This trading plan covers the exercise and sale of stock options, with such sales limited to an amount reasonably estimated such that the net proceeds from the sale are sufficient to cover the exercise cost and taxes associated with the exercise of the stock options.