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Form SCHEDULE 13D Seaport Therapeutics, Filed by: ARCH Venture Fund XII, L.P.

May 6, 2026 4:27 PM





If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).




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SCHEDULE 13D






SCHEDULE 13D






SCHEDULE 13D






SCHEDULE 13D






SCHEDULE 13D






SCHEDULE 13D






SCHEDULE 13D






SCHEDULE 13D


ARCH Venture Fund XII, L.P.
Signature:ARCH Venture Partners XII, L.P.
Name/Title:its General Partner
Date:05/06/2026
Signature:ARCH Venture Partners XII, LLC
Name/Title:its General Partner
Date:05/06/2026
Signature:/s/ Mark McDonnell*
Name/Title:Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director
Date:05/06/2026
ARCH Venture Partners XII, L.P.
Signature:ARCH Venture Partners XII, LLC
Name/Title:its General Partner
Date:05/06/2026
Signature:/s/ Mark McDonnell*
Name/Title:Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director
Date:05/06/2026
ARCH Venture Partners XII, LLC
Signature:/s/ Mark McDonnell*
Name/Title:Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director
Date:05/06/2026
Robert Nelsen
Signature:/s/ Mark McDonnell*
Name/Title:Mark McDonnell, as Attorney-in-Fact for Robert Nelsen
Date:05/06/2026
Keith Crandell
Signature:/s/ Mark McDonnell*
Name/Title:Mark McDonnell, as Attorney-in-Fact for Keith Crandell
Date:05/06/2026
Kristina Burow
Signature:/s/ Mark McDonnell*
Name/Title:Mark McDonnell, as Attorney-in-Fact for Kristina Burow
Date:05/06/2026
Steven Gillis
Signature:/s/ Mark McDonnell*
Name/Title:Mark McDonnell, as Attorney-in-Fact for Steven Gillis
Date:05/06/2026
Comments accompanying signature:
*This Schedule 13D was executed by Mark McDonnell pursuant to a Power of Attorney filed as Exhibit 24.2 to the Form 3 relating to the beneficial ownership of shares of Neumora Therapeutics, Inc. by the Reporting Persons filed with the Securities Exchange Commission on September 14, 2023 and incorporated herein in its entirety by reference.

ATTACHMENTS / EXHIBITS

EX-99.1

Categories

SEC Filings