RA CAPITAL MANAGEMENT, L.P. - 13 Mar 2026 SCHEDULE 13D/A Report for ACUMEN PHARMACEUTICALS, INC. Common Stock, $0.0001 par value per share (ABOS)

Filing Manager: RA CAPITAL MANAGEMENT, L.P.
Reporting Manager: RA Capital Management, L.P.
Security: ACUMEN PHARMACEUTICALS, INC. Common Stock, $0.0001 par value per share
Symbol: ABOS
Shares outstanding: 71,531,081 shares
Disclosed Ownership: 21,101,669 shares
Ownership: 30%
Form type: SCHEDULE 13D/A
Filing time: 17 Mar 2026, 16:33:12 UTC
Date of event: 13 Mar 2026
Previous filing: 31 Mar 2025
SEC: View on sec.gov

Reporting Managers (4)

Name	Ownership	Shares Owned	shared voting power	Signature	Title	CIK
RA Capital Management, L.P.	30%	21,101,669	21,101,669	/s/ Peter Kolchinsky	By Peter Kolchinsky, Authorized Signatory	0001346824
Peter Kolchinsky	30%	21,101,669	21,101,669	/s/ Peter Kolchinsky	Peter Kolchinsky	0001384859
Rajeev Shah	30%	21,101,669	21,101,669	/s/ Rajeev Shah	Rajeev Shah	0001619841
RA Capital Healthcare Fund, L.P.	27%	19,103,785	19,103,785	/s/ Peter Kolchinsky	By RA Capital Healthcare Fund GP, LLC, its General Partner, By Peter Kolchinsky, Manager	0001315082