RA CAPITAL MANAGEMENT, L.P. - 12 Aug 2026 Form 4 Insider Report for Septerna, Inc. (SEPN)

Reporting relationship: Director, 10%+ Owner
Issuer ticker: SEPN
Reported as of: 12 Aug 2026
Net transaction value: -$63,452,500
SEC form: 4
Accepted by SEC: 14 Aug 2026, 17:11:35 UTC
Prior SEC filing: 31 Jul 2026
Source filing: View source filing
Reporting owner signature: /s/ Peter Kolchinsky, Manager of RA Capital Management, L.P.

Key filing fact

RA CAPITAL MANAGEMENT, L.P. filed Form 4 for Septerna, Inc. (SEPN) on 14 Aug 2026.

Key facts

This page summarizes RA CAPITAL MANAGEMENT, L.P.'s Form 4 filing for Septerna, Inc. (SEPN).
2 reported transactions and 0 derivative rows are listed below.
Accepted by SEC: 14 Aug 2026, 17:11.

Change

Previous filing in this sequence was filed on 31 Jul 2026.
Current net transaction value: -$63,452,500.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (5)

CIK 0001346824 Primary reporting owner

RA CAPITAL MANAGEMENT, L.P.

Relationship: Director, 10%+ Owner
Address: 200 BERKELEY STREET, 18TH FLOOR, BOSTON
Signature: /s/ Peter Kolchinsky, Manager of RA Capital Management, L.P.
Signature date: 14 Aug 2026

CIK 0001315082

RA Capital Healthcare Fund LP

Relationship: Director, 10%+ Owner
Address: 200 BERKELEY STREET, 18TH FLOOR, BOSTON
Signature: /s/ Peter Kolchinsky, Manager of RA Capital Healthcare Fund GP, LLC, the General Partner of RA Capital Healthcare Fund, L.P.
Signature date: 14 Aug 2026

CIK 0001883840

RA Capital Nexus Fund III, L.P.

Relationship: Director
Address: 200 BERKELEY STREET, 18TH FLOOR, BOSTON
Signature: /s/ Peter Kolchinsky, Manager of RA Capital Nexus Fund III GP, LLC, the General Partner of RA Capital Nexus Fund III, L.P.
Signature date: 14 Aug 2026

CIK 0001384859

Kolchinsky Peter

Relationship: Director, 10%+ Owner
Address: C/O RA CAPITAL MANAGEMENT, L.P., 200 BERKELEY STREET, 18TH FLOOR, BOSTON
Signature: /s/ Peter Kolchinsky, individually
Signature date: 14 Aug 2026

CIK 0001619841

Shah Rajeev M.

Relationship: Director, 10%+ Owner
Address: C/O RA CAPITAL MANAGEMENT, L.P., 200 BERKELEY STREET, 18TH FLOOR, BOSTON
Signature: /s/ Rajeev Shah, individually
Signature date: 14 Aug 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

SEPN transaction

Common Stock

Sale

Transaction value: $31,726,250
Shares: -746,500
Change %: -14%
Price: $42.50
Shares after: 4,777,415
Date: 12 Aug 2026
Ownership: See footnotes
Footnotes: F1, F2

SEPN transaction

Common Stock

Sale

Transaction value: $31,726,250
Shares: -746,500
Change %: -14%
Price: $42.50
Shares after: 4,777,415
Date: 12 Aug 2026
Ownership: See footnotes
Footnotes: F1, F2

SEPN transaction

Common Stock

Sale

Transaction value: $31,726,250
Shares: -746,500
Change %: -14%
Price: $42.50
Shares after: 4,777,415
Date: 12 Aug 2026
Ownership: See footnotes
Footnotes: F1, F2

SEPN transaction

Common Stock

Sale

Transaction value: $31,726,250
Shares: -746,500
Change %: -14%
Price: $42.50
Shares after: 4,777,415
Date: 12 Aug 2026
Ownership: See footnotes
Footnotes: F1, F2

SEPN transaction

Common Stock

Sale

Transaction value: $31,726,250
Shares: -746,500
Change %: -14%
Price: $42.50
Shares after: 4,777,415
Date: 12 Aug 2026
Ownership: See footnotes
Footnotes: F1, F2

SEPN transaction

Common Stock

Sale

Transaction value: $31,726,250
Shares: -746,500
Change %: -51%
Price: $42.50
Shares after: 725,443
Date: 12 Aug 2026
Ownership: See footnotes
Footnotes: F1, F3

SEPN transaction

Common Stock

Sale

Transaction value: $31,726,250
Shares: -746,500
Change %: -51%
Price: $42.50
Shares after: 725,443
Date: 12 Aug 2026
Ownership: See footnotes
Footnotes: F1, F3

SEPN transaction

Common Stock

Sale

Transaction value: $31,726,250
Shares: -746,500
Change %: -51%
Price: $42.50
Shares after: 725,443
Date: 12 Aug 2026
Ownership: See footnotes
Footnotes: F1, F3

SEPN transaction

Common Stock

Sale

Transaction value: $31,726,250
Shares: -746,500
Change %: -51%
Price: $42.50
Shares after: 725,443
Date: 12 Aug 2026
Ownership: See footnotes
Footnotes: F1, F3

SEPN transaction

Common Stock

Sale

Transaction value: $31,726,250
Shares: -746,500
Change %: -51%
Price: $42.50
Shares after: 725,443
Date: 12 Aug 2026
Ownership: See footnotes
Footnotes: F1, F3

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 3 footnotes

Footnote F1

RA Capital Management, L.P. (the "Adviser") is the investment manager for RA Capital Healthcare Fund, L.P. (the "Fund") and RA Capital Nexus Fund III, L.P. (the "Nexus Fund III"). 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 III, 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.

Footnote F2

Held directly by the Fund.

Footnote F3

Held directly by the Nexus Fund III.

SEC remarks

Jake Simson, a Partner of the Adviser, serves on the Issuer's board of directors.