Whetstone/Atterbury amend 8.6% stake in Sera Prognostics (NASDAQ: SERA)

Rhea-AI Filing Summary

Sera Prognostics reports amended Schedule 13G ownership by Whetstone Capital Advisors, LLC and David Atterbury. The filing states the Reporting Persons beneficially own 3,306,889 shares of Class A Common Stock, representing 8.6% of the class. The signature dates are 05/01/2026.

Insights

Corporate Governance Analyst

Amendment updates an existing passive 13G stake to show 8.6% ownership.

The filing records that Whetstone Capital Advisors, LLC and David Atterbury report beneficial ownership of 3,306,889 shares and shared voting/dispositive power over that amount. The filing is an ownership disclosure under Schedule 13G/A.

Implications are procedural: holdings are now disclosed as amended. Subsequent filings would show any change; timing here is shown by the 05/01/2026 signature date.

Key Figures

Beneficial ownership: 3,306,889 shares Percent of class: 8.6% Signature date: 05/01/2026

3 metrics

Beneficial ownership 3,306,889 shares Amount beneficially owned reported in Item 4

Percent of class 8.6% Percent of Class A Common Stock reported in Item 4

Signature date 05/01/2026 Signature dates for the Reporting Persons at end of filing

Key Terms

beneficially owned, shared dispositive power, Schedule 13G/A

3 terms

beneficially owned regulatory

"Amount beneficially owned: 3,306,889"

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 dispositive power regulatory

"Shared Dispositive Power 3,306,889.00"

Schedule 13G/A regulatory

"SCHEDULE 13G/A (Amendment No. 2 )"

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.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 2)

SERA PROGNOSTICS, INC.

(Name of Issuer)

Class A Common Stock, par value $0.0001 per share

(Title of Class of Securities)

81749D107

(CUSIP Number)

03/31/2026

(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): 81749D107

1

Names of Reporting Persons

Whetstone Capital Advisors, 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

KANSAS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power
6	Shared Voting Power 3,306,389.00
7	Sole Dispositive Power
8	Shared Dispositive Power 3,306,889.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,306,889.00

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)

8.6 %

12

Type of Reporting Person (See Instructions)

OO, IA

SCHEDULE 13G

CUSIP Number(s): 81749D107

1

Names of Reporting Persons

David Atterbury

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
6	Shared Voting Power 3,306,889.00
7	Sole Dispositive Power
8	Shared Dispositive Power 3,306,889.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,306,889.00

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)

8.6 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: SERA PROGNOSTICS, INC.
(b)	Address of issuer's principal executive offices: 2749 E. PARLEYS WAY, SUITE 200, SALT LAKE CITY, UTAH, 84109.
Item 2.
(a)	Name of person filing: Whetstone Capital Advisors, LLC ("WCA") and Mr. David Atterbury (collectively the "Reporting Persons").
(b)	Address or principal business office or, if none, residence: 2001 Shawnee Mission Parkway, Shawnee Mission, Kansas 66205
(c)	Citizenship: United States of America
(d)	Title of class of securities: Class A Common Stock, par value $0.0001 per share
(e)	CUSIP No.: 81749D107
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: 3,306,889
(b)	Percent of class: 8.6%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote:
	(ii) Shared power to vote or to direct the vote: 3,306,889
	(iii) Sole power to dispose or to direct the disposition of:
	(iv) Shared power to dispose or to direct the disposition of: 3,306,889
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.
	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.
	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 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.

Whetstone Capital Advisors, LLC

Signature:	/s/ David Atterbury
Name/Title:	Manager
Date:	05/01/2026

David Atterbury

Signature:	/s/ David Atterbury
Name/Title:	David Atterbury
Date:	05/01/2026

FAQ

What stake does Whetstone Capital Advisors report in SERA?

Whetstone Capital Advisors reports beneficial ownership of 3,306,889 shares of Class A Common Stock, equal to 8.6% of the class. The filing lists shared voting and dispositive power over those shares and is signed on 05/01/2026.

Who are the reporting persons on the Schedule 13G/A for SERA?

The reporting persons are Whetstone Capital Advisors, LLC and David Atterbury. The filing shows both names and lists the same beneficial ownership amount of 3,306,889 shares with shared voting and dispositive power.

Does the filing indicate control or sole voting power for the shares?

The filing shows shared voting power and shared dispositive power of 3,306,889 shares. No sole voting or sole dispositive power is indicated for the Reporting Persons in the provided excerpt.

What date is associated with the Schedule 13G/A amendment for SERA?

The signatures on the amendment are dated 05/01/2026. The header also lists 03/31/2026 in the excerpt, while the formal signature dates are 05/01/2026 as shown in the filing.