SCHEDULE 13G/A 0001224962 XXXXXXXX LIVE 2 Common Stock, $0.0001 par value per share 03/31/2025 0001658551 Amylyx Pharmaceuticals, Inc. 03237H101 43 Thorndike Street Cambridge MA 02141 Rule 13d-1(c) Perceptive Advisors LLC DE 0 7874348 0 7874348 7874348 N 8.8 IA Joseph Edelman X1 0 7874348 0 7874348 7874348 N 8.8 IN Perceptive Life Sciences Master Fund, Ltd. E9 0 7874348 0 7874348 7874348 N 8.8 CO Amylyx Pharmaceuticals, Inc. 43 Thorndike Street, Cambridge, MA 02141 The names of the persons filing this report (collectively, the "Reporting Persons") with respect to shares of Common Stock, par value $0.0001 per share (the "Common Stock") of Amylyx Pharmaceuticals, Inc. (the "Issuer") are: (i) Perceptive Advisors LLC ("Perceptive Advisors") (ii) Joseph Edelman ("Mr. Edelman") (iii) Perceptive Life Sciences Master Fund, Ltd. (the "Master Fund") The address of the principal business office of each of the Reporting Persons is: 51 Astor Place, 10th Floor, New York, NY 10003 Perceptive Advisors is a Delaware limited liability company. Mr. Edelman is a United States citizen. The Master Fund is a Cayman Islands corporation. Y The information required by this item with respect to each Reporting Person is set forth in Rows 5 through 9 of the cover pages to this Schedule 13G. The ownership percentages reported are based on 89,141,087 shares of Common Stock outstanding as of April 28, 2025, as reported in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on May 8, 2025. The Master Fund directly holds 7,874,348 shares of Common Stock. Perceptive Advisors serves as the investment manager to the Master Fund. Mr. Edelman is the managing member of Perceptive Advisors. Perceptive Advisors: 8.8% Mr. Edelman: 8.8% Master Fund: 8.8 Perceptive Advisors: 0 Mr. Edelman: 0 Master Fund: 0 Perceptive Advisors: 7,874,348 Mr. Edelman: 7,874,348 Master Fund: 7,874,348 Perceptive Advisors: 0 Mr. Edelman: 0 Master Fund: 0 Perceptive Advisors: 7,874,348 Mr. Edelman: 7,874,348 Master Fund: 7,874,348 Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. Perceptive Advisors LLC /s/ Joseph Edelman 05/15/2025 Joseph Edelman /s/ Joseph Edelman 05/15/2025 Perceptive Life Sciences Master Fund, Ltd. /s/ Joseph Edelman 05/15/2025