RA CAPITAL MANAGEMENT, L.P. - 26 Jun 2026 Form 4 Insider Report for Septerna, Inc. (SEPN)

Reporting relationship: Director, 10%+ Owner
Issuer ticker: SEPN
Reported as of: 26 Jun 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 30 Jun 2026, 19:52:23 UTC
Prior SEC filing: 29 Jun 2026
Next SEC filing: 01 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 30 Jun 2026.

Key facts

This page summarizes RA CAPITAL MANAGEMENT, L.P.'s Form 4 filing for Septerna, Inc. (SEPN).
1 reported transaction and 5 derivative rows are listed below.
Accepted by SEC: 30 Jun 2026, 19:52.

Change

Previous filing in this sequence was filed on 29 Jun 2026.
Current net transaction value: $0.

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: 30 Jun 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: 30 Jun 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: 30 Jun 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: 30 Jun 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: 30 Jun 2026

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

SEPN transaction Derivative

Stock Option (Right to Buy)

Award

Transaction value
Shares: +15,000
Change %
Price: $0.000000^*
Shares after: 15,000
Date: 26 Jun 2026
Ownership: See Footnotes
Underlying class: Common Stock
Underlying amount: 15,000
Exercise price: $37.34
Footnotes: F1, F2, F3

SEPN transaction Derivative

Stock Option (Right to Buy)

Award

Transaction value
Shares: +15,000
Change %
Price: $0.000000^*
Shares after: 15,000
Date: 26 Jun 2026
Ownership: See Footnotes
Underlying class: Common Stock
Underlying amount: 15,000
Exercise price: $37.34
Footnotes: F1, F2, F3

SEPN transaction Derivative

Stock Option (Right to Buy)

Award

Transaction value
Shares: +15,000
Change %
Price: $0.000000^*
Shares after: 15,000
Date: 26 Jun 2026
Ownership: See Footnotes
Underlying class: Common Stock
Underlying amount: 15,000
Exercise price: $37.34
Footnotes: F1, F2, F3

SEPN transaction Derivative

Stock Option (Right to Buy)

Award

Transaction value
Shares: +15,000
Change %
Price: $0.000000^*
Shares after: 15,000
Date: 26 Jun 2026
Ownership: See Footnotes
Underlying class: Common Stock
Underlying amount: 15,000
Exercise price: $37.34
Footnotes: F1, F2, F3

SEPN transaction Derivative

Stock Option (Right to Buy)

Award

Transaction value
Shares: +15,000
Change %
Price: $0.000000^*
Shares after: 15,000
Date: 26 Jun 2026
Ownership: See Footnotes
Underlying class: Common Stock
Underlying amount: 15,000
Exercise price: $37.34
Footnotes: F1, F2, 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

The shares underlying the stock option vest in full upon the earlier of (i) June 26, 2027 or (ii) the date of the Issuer's next annual meeting of stockholders, subject to Dr. Simson's continued service to the Issuer through such vesting date.

Footnote F2

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 F3

Under Dr. Simson's arrangement with the Adviser, Dr. Simson holds the option for the benefit of the Fund and the Nexus Fund III. Dr. Simson is obligated to turn over to the Adviser any net cash or stock received upon exercise of the option, which will offset advisory fees owed by the Fund and the Nexus Fund III to the Adviser. The Reporting Persons therefore disclaim beneficial ownership of the option and underlying common stock.

SEC remarks

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