SEC Form DEFA14A filed by Amylyx Pharmaceuticals Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934 (Amendment No. )

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

AMYLYX PHARMACEUTICALS, INC.

(Name of registrant as specified in its charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

Online Go to www.envisionreports.com/AMLX or scan the QR code — login details are located in the shaded bar below. Stockholder Meeting Notice Important Notice Regarding the Availability of Proxy Materials for the Amylyx Pharmaceuticals, Inc. Stockholder Meeting to be Held on Thursday, June 4, 2026. Under Securities and Exchange Commission rules, you are receiving this notice that the proxy materials for the annual stockholder meeting are available on the Internet. Follow the instructions below to view the materials and vote online or request a copy. The items to be voted on and location of the annual meeting are on the reverse side. Your vote is important! This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. We encourage you to access and review all of the important information contained in the proxy materials before voting. The 2026 proxy statement and annual report to stockholders are available at: www.envisionreports.com/AMLX Easy Online Access — View your proxy materials and vote. Step 1: Go to www.envisionreports.com/AMLX. Step 2: Click on Cast Your Vote or Request Materials. Step 3: Follow the instructions on the screen to log in. Step 4: Make your selections as instructed on each screen for your delivery preferences. Step 5: Vote your shares. When you go online, you can also help the environment by consenting to receive electronic delivery of future materials. Obtaining a Copy of the Proxy Materials – If you want to receive a paper or email copy of the proxy materials, you must request one. If you do not request it, you will not otherwise receive a paper or email copy. There is no charge to you for requesting a copy. Please make your request as instructed on the reverse side of this form on or before May 25, 2026 to facilitate timely delivery. 2NOT 049Y8A

Stockholder Meeting Notice The 2026 Annual Meeting of Stockholders of Amylyx Pharmaceuticals, Inc. will be held on Thursday, June 4, 2026, at 9:00 a.m. ET, virtually via the internet at meetnow.global/M75QLG2. To access the virtual meeting, you must have the information that is printed in the shaded bar located on the reverse side of this form. Proposals to be voted on at the meeting are listed below along with the Board of Directors’ recommendations. The Board of Directors recommends a vote FOR all the nominees listed, and FOR Proposals 2 and 3: 1. Election of Directors: To elect the following persons to our board of directors, each to serve as a Class II director until the 2029 Annual Meeting of Stockholders and until their successor has been duly elected and qualified, or until such director’s earlier death, resignation or removal: 01 -George Mclean Milne Jr., Ph.D. 02 -Paul Fonteyne 2. To ratify the appointment of Deloitte & Touche LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2026. 3. To approve, on a non-binding, advisory basis, the compensation of our named executive officers. PLEASE NOTE – YOU CANNOT VOTE BY RETURNING THIS NOTICE. To vote your shares you must go online or request a paper copy of the proxy materials to receive a proxy card. Here’s how to order a copy of the proxy materials and select delivery preferences: Current and future delivery requests can be submitted using the options below. If you request an email copy, you will receive an email with a link to the current meeting materials. PLEASE NOTE: You must use the number in the shaded bar on the reverse side when requesting a copy of the proxy materials. — Internet – Go to www.envisionreports.com/AMLX. Click Cast Your Vote or Request Materials. — Phone – Call us free of charge at 1-866-641-4276. — Email – Send an email to [email protected] with “Proxy Materials Amylyx Pharmaceuticals, Inc.” in the subject line. Include your full name and address, plus the number located in the shaded bar on the reverse side of this form, and state that you want a paper copy of the meeting materials. To facilitate timely delivery, all requests for a paper copy of proxy materials must be received by May 25, 2026.