United States securities and exchange commission logo December 20, 2023 James Frates Chief Financial Officer Amylyx Pharmaceuticals, Inc. 43 Thorndike St. Cambridge, MA 02141 Re: Amylyx Pharmaceuticals, Inc. Form 10-K for the Fiscal Year Ended December 31, 2022 Filed March 13, 2023 File Number 001-41199 Dear James Frates: We have completed our review of your filing. We remind you that the company and its management are responsible for the accuracy and adequacy of their disclosures, notwithstanding any review, comments, action or absence of action by the staff. Sincerely, Division of Corporation Finance Office of Life Sciences