ProMIS Neurosciences Inc

SPECIAL MEETING OF SHAREHOLDERS

To Be Held on November 17, 2025

This proxy statement contains information about the Special Meeting of Shareholders of ProMIS Neurosciences Inc. (the “Special Meeting”), to be held on Monday, November 17, 2025 at 8:00 a.m., Eastern Time. This Special Meeting will be a virtual meeting, which will be conducted via live webcast. In order to attend the Special Meeting, you must register atwww.virtualshareholdermeeting.com/PMN2025SM. Upon completing your registration, you will receive further instructions via email, including a unique link that will allow you access to the Special Meeting and to vote and submit questions during the Special Meeting. There will not be a physical meeting location, and shareholders will not be able to attend the Special Meeting in person. Further information about how to attend the Special Meeting online is included in this proxy statement below. Except where the context otherwise requires, references to “ProMIS Neurosciences,” “ProMIS,” “Company,” “we,” “us,” “our” and similar terms refer to ProMIS Neurosciences Inc. and its consolidated subsidiaries.

This proxy statement summarizes information about the proposals to be considered at the Special Meeting and other information you may find useful in determining how to vote. We are making this proxy statement and the related proxy card, available to shareholders for the first time on or about October 8, 2025.

Pursuant to rules adopted by the Securities and Exchange Commission (the “SEC”) and the Canadian Securities Administrators (the “CSA”), we are providing access to our proxy materials over the Internet instead of printing and mailing our proxy materials. As a result, we are mailing to our shareholders a Notice of Internet Availability of Proxy Materials (the “Notice”), instead of a paper copy of this proxy statement. We plan to send the Notice on or about October 8, 2025. The Notice contains instructions on how each of our shareholders may access and review the proxy materials, including the Notice of Special Meeting, proxy statement and proxy card, on the website referred to in the Notice. The Notice also contains instructions on how each of our shareholders may request that a paper copy of our proxy materials, including this proxy statement and a form of proxy card, be sent to such shareholder by mail.

Important Notice Regarding the Availability of Proxy Materials for**

**the Special Meeting of Shareholders to be Held on November 17, 2025:

This proxy statement is available for viewing, printing, and downloading atwww.proxyvote.com**.**

This proxy statement is also available on the SEC’s website at www.sec.gov and on the System of Electronic Document Analysis and Retrieval + (“SEDAR+”) at www.sedarplus.ca.

QUESTIONS AND ANSWERS ABOUT THE SPECIAL MEETING AND VOTING