Bain Capital Life Sciences Fund II, L.P. - 12 Nov 2025 SCHEDULE 13D/A Report for Mersana Therapeutics, Inc. Common Stock, par value $0.0001 per share (MRSN)

Filing Manager
Bain Capital Life Sciences Fund II, L.P.
Reporting Manager
BCLS II Investco, LP
Security
Mersana Therapeutics, Inc. Common Stock, par value $0.0001 per share
Symbol
MRSN
Shares outstanding
4.97M shares
Disclosed Ownership
199K shares
Ownership
4%
Form type
SCHEDULE 13D/A
Filing time
13 Nov 2025, 18:45:02 UTC
Date of event
12 Nov 2025
SEC
View on sec.gov

Reporting Managers (3)

Name Ownership Shares Owned sole voting power shared voting power Signature Title CIK
Bain Capital Life Sciences Fund II, L.P. 2.6% 132K 0 132K /s/ Andrew Hack Andrew Hack, Partner of Bain Capital Life Sciences Investors, LLC 0001773187
BCIP Life Sciences Associates, LP 0.3% 16K 0 16K /s/ Andrew Hack Andrew Hack, Authorized Signatory of Boylston Coinvestors, LLC 0001702921
BCLS II Investco, LP 4% 199K 0 199K /s/ Andrew Hack Andrew Hack, Partner of Bain Capital Life Sciences Investors, LLC 0001818893