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Form 4 Acumen Pharmaceuticals, For: Jun 03 Filed by: Kolchinsky Peter

June 5, 2026 5:13 PM
FORM 4 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
1. Name and Address of Reporting Person *
RA CAPITAL MANAGEMENT, L.P.
(Last) (First) (Middle)
200 BERKELEY STREET, 18TH FLOOR
(Street)
BOSTON MA 02116
(City) (State) (Zip)
2. Issuer Name and Ticker or Trading Symbol
Acumen Pharmaceuticals, Inc. [ ABOS ] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
X Director X 10% Owner
Officer (give title below) Other (specify below)
3. Date of Earliest Transaction (Month/Day/Year)
06/03/2026
4. If Amendment, Date of Original Filed (Month/Day/Year)
 6. Individual or Joint/Group Filing (Check Applicable Line)
Form filed by One Reporting Person
X Form filed by More than One Reporting Person
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 06/03/2026 A 35,500 (1) A $ 0 48,300 I See footnotes (2) (3)
Common Stock 19,103,785 I See footnotes (2) (4)
Common Stock 1,300,034 I See footnotes (2) (5)
Common Stock 588,850 I See footnotes (2) (6)
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 6. Date Exercisable and Expiration Date (Month/Day/Year) 7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Option (Right to Buy) $ 2.29 06/03/2026 A 53,250 (7) 06/03/2036 Common Stock 53,250 $ 0 53,250 I See Footnotes (2) (3)
Explanation of Responses:
1. Represents a restricted stock unit ("RSU") award to Laura Stoppel. Each RSU represents a contingent right to receive one share of the Issuer's Common Stock. The RSUs will vest in full on the earlier of the first anniversary of the date of grant or the 2027 annual stockholder meeting, subject to Dr. Stoppel's continuous service through such vesting date.
2. RA Capital Management, L.P. (the "Adviser") is the investment manager for RA Capital Healthcare Fund, L.P. (the "Fund"), RA Capital Nexus Fund II, L.P. (the "Nexus Fund II") and a separately managed account (the "Account"). The general partner of the Adviser is RA Capital Management GP, LLC (the "Adviser GP"), of which Dr. Peter Kolchinsky and Mr. Rajeev Shah are the managing members. Each of the Adviser, the Adviser GP, the Fund, the Nexus Fund II, Dr. Kolchinsky, and Mr. Shah disclaims beneficial ownership of any of the reported securities, except to the extent of its or his respective pecuniary interest therein.
3. Under Dr. Stoppel's arrangement with the Adviser, Dr. Stoppel holds the RSUs and the option for the benefit of the Fund, the Nexus Fund II and the Account. Dr. Stoppel is obligated to turn over to the Adviser any net cash or stock received upon exercise of the option or settlement of the RSUs, as applicable, which will offset advisory fees owed by the Fund, the Nexus Fund II and the Account to the Adviser. The Reporting Persons therefore disclaim beneficial ownership of the RSUs, the option and the underlying common stock.
4. Held directly by the Fund.
5. Held directly by the Nexus Fund II.
6. Held directly by the Account.
7. Represents the award of an option to Dr. Stoppel. The shares subject to the option will vest in full on the earlier of the first anniversary of the date of grant or the 2027 annual stockholder meeting, subject to Dr. Stoppel's continuous service through such vesting date.
Remarks:
Laura Stoppel, a Principal of the Adviser, serves on the Issuer's board of directors.
/s/ Peter Kolchinsky, Manager of RA Capital Management, L.P. 06/05/2026
** Signature of Reporting Person Date
/s/ Peter Kolchinsky, Manager of RA Capital Healthcare Fund GP, LLC, the General Partner of RA Capital Healthcare Fund, L.P. 06/05/2026
** Signature of Reporting Person Date
/s/ Peter Kolchinsky, Manager of RA Capital Nexus Fund II GP, LLC, the General Partner of RA Capital Nexus Fund II, L.P. 06/05/2026
** Signature of Reporting Person Date
/s/ Peter Kolchinsky, individually 06/05/2026
** Signature of Reporting Person Date
/s/ Rajeev Shah, individually 06/05/2026
** Signature of Reporting Person Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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