Acumen 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

Filed by the Registrantx

Filed by a Party other than the Registranto

Check the appropriate box:

Acumen 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):

1210-1220 Washington Street

Suite 210

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

To Be Held On June 3, 2026

Dear Stockholder:

You are cordially invited to attend the 2026 Annual Meeting of Stockholders (the “Annual Meeting”) of Acumen Pharmaceuticals, Inc., a Delaware corporation (the “Company”). The meeting will be held on Wednesday, June 3, 2026 at 11:00 a.m. Eastern Time through a live video webcast atwww.proxydocs.com/ABOS. You will not be able to attend the meeting in person. The meeting will be held for the following purposes:

1. To elect three Class II directors, George Golumbeski, Ph.D., Derrell Porter, M.D. and Laura Stoppel, Ph.D., to the Board of Directors, each to hold office until the 2029 Annual Meeting of Stockholders and until his or her successor shall have been duly elected and qualified.

2. To ratify the appointment by the Audit Committee of the Board of Directors of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2026.

3. To approve the Company’s Amended and Restated 2021 Equity Incentive Plan.

4. To conduct any other business properly brought before the meeting or any adjournments, continuations, or postponements thereof.

These items of business are more fully described in the Proxy Statement for our Annual Meeting (the “Proxy Statement”) accompanying this notice.

We have elected to provide Internet access to our proxy materials, which include the proxy statement accompanying this notice, in lieu of mailing printed copies. Providing our Annual Meeting materials via the Internet reduces the costs associated with our Annual Meeting and lowers our environmental impact, all without negatively affecting our stockholders’ ability to timely access the Annual Meeting materials.

On or about April 23, 2026, we expect to mail to our stockholders a Notice of Internet Availability of Proxy Materials (the “Notice”) containing instructions on how to access the Proxy Statement and our annual report (the “2025 Annual Report”) to our stockholders. The Notice provides instructions on how to vote online or by telephone and how to receive a paper copy of proxy materials by mail. The Proxy Statement and our 2025 Annual Report can be accessed directly atwww.proxydocs.com/ABOS.

The record date for the Annual Meeting is April 8, 2026. Only stockholders of record at the close of business on that date may vote at the meeting or any adjournment thereof.

Important Notice Regarding the Availability of Proxy Materials for the Virtual Stockholders’ Meeting to Be Held on Wednesday, June 3, 2026 at 11:00 a.m. Eastern Time.

By Order of the Board of Directors,

Derek Meisner

Chief Legal Officer and Corporate Secretary

Your vote is important. Whether or not you plan to attend the Annual Meeting virtually, please ensure that your shares are voted during the Annual Meeting by promptly signing and returning a proxy card or by using our Internet or telephonic voting system. Even if you have voted by proxy, you may still vote online if you attend the Annual Meeting. Please note, however, that if your shares are held on your behalf by a brokerage firm, bank, or other agent and you wish to vote at the Annual Meeting, you may need to obtain a proxy issued in your name from that record holder. Please contact your broker, bank, or other agent for information about specific requirements if you would like to vote your shares at the meeting.

1210-1220 Washington Street

Suite 210

PROXY STATEMENT

FOR THE 2026 ANNUAL MEETING OF STOCKHOLDERS

June 3, 2026

MEETING AGENDA

TABLE OF CONTENTS