Sell4

Septerna, Inc.

SEPN

Total Value

$63.5M

Net $63.5M sold

Filing Date

Aug 14, 2026

2 transactions

Sales

$63.5M

2 transactions

Trade Summary

On Aug 12, 2026, RA CAPITAL MANAGEMENT, L.P., Insider, sold $63.5M of Septerna, Inc. (SEPN) across 2 transactions. The filing covers Common Stock and reflects net selling of $63.5M. Reported prices ranged from $42.50. Insider transactions are sourced from SEC Form 4 disclosures and should be reviewed alongside company fundamentals and the insider's broader trading history.

Price at the Time of the Trade

SEPN daily price with the insider's sale marked at $42.50.

Sold in the upper half of the 6-month range · the stock trades 4% higher today.

Price data is delayed and provided for context only — not investment advice.

Insider Information

Name: RA CAPITAL MANAGEMENT, L.P.
Role: Insider
Location: BOSTON, MA

Filing Details

Filing Date: Aug 14, 2026
Transaction Date: Aug 12, 2026
Accession Number: 0001231919-26-000938
Form Type: 4
Net Trading Amount: -$63.5M

Non-Derivative Transactions

Date	Security	Shares	Price	Type	Value
Aug 12, 2026	Common Stock	746,500	$42.50	Sale	$31.7M
Aug 12, 2026	Common Stock	746,500	$42.50	Sale	$31.7M

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Footnotes

(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.
(F2)Held directly by the Fund.
(F3)Held directly by the Nexus Fund III.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

RA CAPITAL MANAGEMENT, L.P.

(Last)

(First)

(Middle)

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON

02116

(City)

(State)

(Zip)

2. Issuer Name and Ticker or Trading Symbol
Septerna, Inc. [ SEPN ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
08/12/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	08/12/2026		S		746,500	D	$42.5	4,777,415	I	See footnotes⁽¹⁾⁽²⁾
Common Stock	08/12/2026		S		746,500	D	$42.5	725,443	I	See footnotes⁽¹⁾⁽³⁾

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)

1. Name and Address of Reporting Person^*

RA CAPITAL MANAGEMENT, L.P.

(Last)

(First)

(Middle)

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON

02116

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

RA Capital Healthcare Fund LP

(Last)

(First)

(Middle)

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON

02116

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

RA Capital Nexus Fund III, L.P.

(Last)

(First)

(Middle)

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON

02116

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	10% Owner
	Officer (give title below)	Other (specify below)

1. Name and Address of Reporting Person^*

Kolchinsky Peter

(Last)

(First)

(Middle)

C/O RA CAPITAL MANAGEMENT, L.P.

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON

02116

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Shah Rajeev M.

(Last)

(First)

(Middle)

C/O RA CAPITAL MANAGEMENT, L.P.

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON

02116

(City)

(State)

(Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. 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.

2. Held directly by the Fund.

3. Held directly by the Nexus Fund III.

Remarks:

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

	/s/ Peter Kolchinsky, Manager of RA Capital Management, L.P.	08/14/2026
	/s/ Peter Kolchinsky, Manager of RA Capital Healthcare Fund GP, LLC, the General Partner of RA Capital Healthcare Fund, L.P.	08/14/2026
	/s/ Peter Kolchinsky, Manager of RA Capital Nexus Fund III GP, LLC, the General Partner of RA Capital Nexus Fund III, L.P.	08/14/2026
	/s/ Peter Kolchinsky, individually	08/14/2026
	/s/ Rajeev Shah, individually	08/14/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

Form 4 as rendered by the SEC from accession 0001231919-26-000938.

Septerna, Inc.

Trade Summary

Price at the Time of the Trade

Company Information

Insider Information

Filing Details

Non-Derivative Transactions

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Footnotes

SEC Form 4

SEC Filing

Price at the Time of the Trade

SEC Form 4