Driehaus Capital Management (SEPN) discloses 4.43M-share Septerna stake in 13G/A

Rhea-AI Filing Summary

Driehaus Capital Management LLC reports beneficial ownership of common stock of Septerna, Inc. and amends its disclosure to reflect a change in ownership percentage. Driehaus reports beneficially owning 4,433,058 shares of Septerna common stock, representing 9.83% of the class.

Driehaus has shared voting power and shared dispositive power over all 4,433,058 shares, with no sole voting or dispositive power. The shares are held in numerous client accounts managed by Driehaus on a fully discretionary basis. Driehaus states that, to its knowledge, none of these underlying clients has the right to receive dividends or sale proceeds relating to more than 5% of the class.

Key Figures

Shares beneficially owned: 4,433,058 shares Percent of class: 9.83% Shared voting power: 4,433,058 shares +2 more

5 metrics

Shares beneficially owned 4,433,058 shares Common stock of Septerna, Inc. reported by Driehaus Capital Management LLC

Percent of class 9.83% Percentage of Septerna common stock class beneficially owned by Driehaus

Shared voting power 4,433,058 shares Shares over which Driehaus has shared power to vote or direct the vote

Sole voting power 0 shares Shares over which Driehaus has sole power to vote or direct the vote

Shared dispositive power 4,433,058 shares Shares over which Driehaus has shared power to dispose or direct disposition

Key Terms

beneficially owned, shared voting power, shared dispositive power, dispositive power, +1 more

5 terms

beneficially owned financial

"Amount beneficially owned: 4433058"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

shared voting power financial

"Shared Voting Power 4,433,058.00"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

shared dispositive power financial

"Shared Dispositive Power 4,433,058.00"

dispositive power financial

"has dispositive power. To the best of DCM's knowledge"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

Schedule 13G/A regulatory

"This amendment is being filed to reflect the change"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

FAQ

What percentage of Septerna, Inc. (SEPN) does Driehaus Capital Management LLC own?

Driehaus Capital Management LLC reports beneficial ownership of 9.83% of Septerna, Inc.’s common stock, corresponding to 4,433,058 shares. This reflects an updated ownership percentage disclosed in the amended Schedule 13G/A filing.

How many Septerna, Inc. (SEPN) shares does Driehaus Capital Management LLC control?

Driehaus Capital Management LLC reports beneficial ownership and control, through shared powers, of 4,433,058 Septerna common shares. It has shared voting and dispositive power over all these shares and no sole voting or dispositive authority.

Does Driehaus Capital Management LLC hold Septerna (SEPN) shares with sole or shared voting power?

Driehaus reports 0 shares with sole voting power and 4,433,058 shares with shared voting power. It similarly reports 0 shares with sole dispositive power and 4,433,058 shares with shared dispositive power over Septerna stock.

Who actually holds the Septerna, Inc. (SEPN) shares reported by Driehaus Capital Management LLC?

The Septerna shares are held in numerous client accounts managed by Driehaus on a fully discretionary basis. Driehaus reports the position because it may have voting and has dispositive power, not because it is the economic owner of all those shares.

Do any Driehaus clients own more than 5% of Septerna, Inc. (SEPN)?

According to Driehaus, to the best of its knowledge, none of the referenced clients has the right to receive dividends or sale proceeds relating to more than 5% of Septerna’s common stock class.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/14/2026 - 07:32 AM Accepted by SEC EDGAR 08/14/2026 - 07:32 AM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 3)

Septerna, Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

81734D104

(CUSIP Number)

06/30/2026

(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)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 81734D104

1

Names of Reporting Persons

DRIEHAUS CAPITAL MANAGEMENT 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 4,433,058.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 4,433,058.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

4,433,058.00

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)

9.83 %

12

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person: This amendment is being filed to reflect the change in our percentage of ownership in Septerna, Inc. (SEPN).

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Septerna, Inc.
(b)	Address of issuer's principal executive offices: 250 East Grand Ave., Suite 65, South San Francisco, California, 94080
Item 2.
(a)	Name of person filing: Driehaus Capital Management LLC
(b)	Address or principal business office or, if none, residence: 25 East Erie Street, Chicago, Illinois 60611
(c)	Citizenship: USA
(d)	Title of class of securities: Common Stock
(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: 4433058
(b)	Percent of class: 9.83 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 0
	(ii) Shared power to vote or to direct the vote: 4433058
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 4433058
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. The shares reported by Driehaus Capital Management LLC (DCM) are held by numerous clients on a fully discretionary basis in accounts managed by DCM. Securities held in these clients' accounts are included in this report to reflect that DCM may have voting power and has dispositive power. To the best of DCM's knowledge, none of the referenced clients have the right to receive dividends or direct proceeds from the sale of interests relating to more than 5% of the class.
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.
	Not Applicable
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 acquired and are held in the ordinary course of business and 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.

DRIEHAUS CAPITAL MANAGEMENT LLC

Signature:	Janet McWilliams
Name/Title:	General Counsel
Date:	08/14/2026