Biotechnology Value Fund group discloses 3.8% Septerna (SEPN) ownership in 13G/A

Rhea-AI Filing Summary

Septerna, Inc. received an updated ownership report from Biotechnology Value Fund and affiliated entities on a Schedule 13G/A Amendment No. 2. As of the close of business on December 31, 2025, BVF, BVF2 and Biotechnology Value Trading Fund OS together beneficially owned 1,720,782 shares of Septerna common stock through various funds and a managed account.

This position represents approximately 3.8% of Septerna’s 44,774,192 shares outstanding as of November 4, 2025, as reported by the company. The reporting group certifies that the shares were not acquired and are not held for the purpose of changing or influencing control of Septerna.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 2)

Septerna, Inc.

(Name of Issuer)

Common Stock, $0.001 par value per share

(Title of Class of Securities)

81734D104

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 81734D104

1

Names of Reporting Persons

BIOTECHNOLOGY VALUE FUND L P

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 919,814.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 919,814.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

919,814.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.0 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

CUSIP No. 81734D104

1

Names of Reporting Persons

BVF I GP LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 919,814.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 919,814.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

919,814.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.0 %

12

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13G

CUSIP No. 81734D104

1

Names of Reporting Persons

BIOTECHNOLOGY VALUE FUND II LP

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 671,492.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 671,492.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

671,492.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

1.5 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

CUSIP No. 81734D104

1

Names of Reporting Persons

BVF II GP LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 671,492.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 671,492.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

671,492.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

1.5 %

12

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13G

CUSIP No. 81734D104

1

Names of Reporting Persons

Biotechnology Value Trading Fund OS LP

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 104,119.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 104,119.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

104,119.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

0.2 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

CUSIP No. 81734D104

1

Names of Reporting Persons

BVF Partners OS Ltd.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 104,119.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 104,119.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

104,119.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

0.2 %

12

Type of Reporting Person (See Instructions)

CO

SCHEDULE 13G

CUSIP No. 81734D104

1

Names of Reporting Persons

BVF GP HOLDINGS LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,591,306.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,591,306.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,591,306.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

3.6 %

12

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13G

CUSIP No. 81734D104

1

Names of Reporting Persons

BVF PARTNERS L P/IL

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,720,782.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,720,782.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,720,782.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

3.8 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP No. 81734D104

1

Names of Reporting Persons

BVF INC/IL

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,720,782.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,720,782.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,720,782.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

3.8 %

12

Type of Reporting Person (See Instructions)

CO

SCHEDULE 13G

CUSIP No. 81734D104

1

Names of Reporting Persons

LAMPERT MARK N

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,720,782.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,720,782.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,720,782.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

3.8 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Septerna, Inc.
(b)	Address of issuer's principal executive offices: 250 EAST GRAND AVENUE, SUITE 65, SOUTH SAN FRANCISCO, CA 94080
Item 2.
(a)	Name of person filing: Biotechnology Value Fund, L.P. ("BVF") BVF I GP LLC ("BVF GP") Biotechnology Value Fund II, L.P. ("BVF2") BVF II GP LLC ("BVF2 GP") Biotechnology Value Trading Fund OS LP ("Trading Fund OS") BVF Partners OS Ltd. ("Partners OS") BVF GP Holdings LLC ("BVF GPH") BVF Partners L.P. ("Partners") BVF Inc. Mark N. Lampert ("Mr. Lampert") Each of the foregoing is referred to as a "Reporting Person" and collectively as the "Reporting Persons."
(b)	Address or principal business office or, if none, residence: Biotechnology Value Fund, L.P. 44 Montgomery St., 40th Floor San Francisco, California 94104 BVF I GP LLC 44 Montgomery St., 40th Floor San Francisco, California 94104 Biotechnology Value Fund II, L.P. 44 Montgomery St., 40th Floor San Francisco, California 94104 BVF II GP LLC 44 Montgomery St., 40th Floor San Francisco, California 94104 Biotechnology Value Trading Fund OS LP PO Box 309 Ugland House Grand Cayman, KY1-1104 Cayman Islands BVF Partners OS Ltd. PO Box 309 Ugland House Grand Cayman, KY1-1104 Cayman Islands BVF GP Holdings LLC 44 Montgomery St., 40th Floor San Francisco, California 94104 BVF Partners L.P. 44 Montgomery St., 40th Floor San Francisco, California 94104 BVF Inc. 44 Montgomery St., 40th Floor San Francisco, California 94104 Mark N. Lampert 44 Montgomery St., 40th Floor San Francisco, California 94104
(c)	Citizenship: Biotechnology Value Fund, L.P. Delaware BVF I GP LLC Delaware Biotechnology Value Fund II, L.P. Delaware BVF II GP LLC Delaware Biotechnology Value Trading Fund OS LP Cayman Islands BVF Partners OS Ltd. Cayman Islands BVF GP Holdings LLC Delaware BVF Partners L.P. Delaware BVF Inc. Delaware Mark N. Lampert United States
(d)	Title of class of securities: Common Stock, $0.001 par value per share
(e)	CUSIP No.: 81734D104
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: As of the close of business on December 31, 2025, (i) BVF beneficially owned 919,814 Shares, (ii) BVF2 beneficially owned 671,492 Shares and (iii) Trading Fund OS beneficially owned 104,119 Shares. BVF GP, as the general partner of BVF, may be deemed to beneficially own the 919,814 Shares beneficially owned by BVF. BVF2 GP, as the general partner of BVF2, may be deemed to beneficially own the 671,492 Shares beneficially owned by BVF2. Partners OS, as the general partner of Trading Fund OS, may be deemed to beneficially own the 104,119 Shares beneficially owned by Trading Fund OS. BVF GPH, as the sole member of each of BVF GP and BVF2 GP, may be deemed to beneficially own the 1,591,306 Shares beneficially owned in the aggregate by BVF and BVF2. Partners, as the investment manager of BVF, BVF2 and Trading Fund OS, and the sole member of Partners OS, may be deemed to beneficially own the 1,720,782 Shares beneficially owned in the aggregate by BVF, BVF2 and Trading Fund OS and held in a certain Partners managed account (the "Partners Managed Account"), including 25,357 Shares held in the Partners Managed Account. BVF Inc., as the general partner of Partners, may be deemed to beneficially own the 1,720,782 Shares beneficially owned by Partners. Mr. Lampert, as a director and officer of BVF Inc., may be deemed to beneficially own the 1,720,782 Shares beneficially owned by BVF Inc. The foregoing should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of any Shares owned by another Reporting Person. BVF GP disclaims beneficial ownership of the Shares beneficially owned by BVF. BVF2 GP disclaims beneficial ownership of the Shares beneficially owned by BVF2. Partners OS disclaims beneficial ownership of the Shares beneficially owned by Trading Fund OS. BVF GPH disclaims beneficial ownership of the Shares beneficially owned by BVF and BVF2. Each of Partners, BVF Inc. and Mr. Lampert disclaims beneficial ownership of the Shares beneficially owned by BVF, BVF2 and Trading Fund OS and held in the Partners Managed Account, and the filing of this statement shall not be construed as an admission that any such person or entity is the beneficial owner of any such securities.
(b)	Percent of class: The following percentages are based on 44,774,192 Shares outstanding as of November 4, 2025, as reported in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on November 10, 2025. As of the close of business on December 31, 2025, (i) BVF beneficially owned approximately 2.0% of the outstanding Shares, (ii) BVF2 beneficially owned approximately 1.5% of the outstanding Shares, (iii) Trading Fund OS beneficially owned less than 1% of the outstanding Shares, (iv) BVF GP may be deemed to beneficially own approximately 2.0% of the outstanding Shares, (v) BVF2 GP may be deemed to beneficially own approximately 1.5% of the outstanding Shares, (vi) Partners OS may be deemed to beneficially own less than 1% of the outstanding Shares, (vii) BVF GPH may be deemed to beneficially own approximately 3.6% of the outstanding Shares, and (viii) each of Partners, BVF Inc. and Mr. Lampert may be deemed to beneficially own approximately 3.8% of the outstanding Shares (less than 1% of the outstanding Shares are held in the Partners Managed Account).
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: See Cover Pages Items 5-9.
	(ii) Shared power to vote or to direct the vote: See Cover Pages Items 5-9.
	(iii) Sole power to dispose or to direct the disposition of: See Cover Pages Items 5-9.
	(iv) Shared power to dispose or to direct the disposition of: See Cover Pages Items 5-9.
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(J), so indicate under Item 3(j) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to §240.13d-1(c) or §240.13d-1(d), attach an exhibit stating the identity of each member of the group. See Exhibit 99.1 to the Schedule 13G filed with the Securities and Exchange Commission on November 1, 2024.
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

BIOTECHNOLOGY VALUE FUND L P

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	02/17/2026

BVF I GP LLC

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	02/17/2026

BIOTECHNOLOGY VALUE FUND II LP

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	02/17/2026

BVF II GP LLC

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	02/17/2026

Biotechnology Value Trading Fund OS LP

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	02/17/2026

BVF Partners OS Ltd.

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	02/17/2026

BVF GP HOLDINGS LLC

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	02/17/2026

BVF PARTNERS L P/IL

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	02/17/2026

BVF INC/IL

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	02/17/2026

LAMPERT MARK N

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert
Date:	02/17/2026

FAQ

What ownership stake does Biotechnology Value Fund report in Septerna (SEPN)?

Biotechnology Value Fund and affiliated entities report beneficial ownership of 1,720,782 shares of Septerna common stock, representing approximately 3.8% of outstanding shares based on 44,774,192 shares outstanding as of November 4, 2025, according to the company’s Form 10-Q.

Which entities are included in the Septerna (SEPN) Schedule 13G/A filing?

The filing lists Biotechnology Value Fund, L.P., Biotechnology Value Fund II, L.P., Biotechnology Value Trading Fund OS LP, related general partners and management entities, and Mark N. Lampert as reporting persons, reflecting their aggregated beneficial ownership structure in Septerna shares.

How many Septerna (SEPN) shares does each BVF fund beneficially own?

As of December 31, 2025, BVF held 919,814 shares, BVF2 held 671,492 shares, and Biotechnology Value Trading Fund OS held 104,119 shares. Together with a Partners managed account, these positions total the 1,720,782 shares reported as beneficially owned.

What percentage of Septerna (SEPN) does each BVF-related entity control?

The filing reports BVF at about 2.0%, BVF2 at 1.5%, Trading Fund OS at less than 1%, BVF GP Holdings at about 3.6%, and each of Partners, BVF Inc., and Mark N. Lampert at about 3.8% of Septerna’s outstanding common shares.

Is Biotechnology Value Fund seeking control of Septerna (SEPN)?

No. The reporting group certifies the securities “were not acquired and are not held” for the purpose or effect of changing or influencing control of Septerna, except for activities solely in connection with a nomination under Rule 14a-11, consistent with a passive Schedule 13G filing.

Why is this Septerna (SEPN) Schedule 13G/A labeled Amendment No. 2?

The document is identified as Amendment No. 2, indicating it updates prior ownership disclosures for the same holders. It refreshes beneficial share counts and percentages as of December 31, 2025, based on Septerna’s reported 44,774,192 shares outstanding on November 4, 2025.

Who signed the Septerna (SEPN) Schedule 13G/A on behalf of the reporting persons?

The filing is signed multiple times by Mark N. Lampert as an authorized signatory for the various BVF-related entities, and once in his individual capacity. Each signature is dated February 17, 2026, certifying the accuracy of the information to the best of his knowledge.