Sec Form 3 Filing - BAKER BROS. ADVISORS LP @ SERA PROGNOSTICS, INC. - 2025-02-12

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person BAKER BROS. ADVISORS LP 2. Issuer Name and Ticker or Trading Symbol SERA PROGNOSTICS, INC. [ SERA] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 860 WASHINGTON STREET, 3RD FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 02/12/2025 (Street) NEW YORK, NY10014 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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) Code V Amount (A) or (D) Price Common Stock 432,434 I See Footnotes ( 1 ) ( 2 ) ( 3 ) Common Stock 5,065,736 I See Footnotes ( 2 ) ( 3 ) ( 4 )

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Class B Common Stock ( 5 ) ( 5 ) ( 5 )( 6 ) ( 5 ) Common Stock 66,911 I See Footnotes ( 1 ) ( 2 ) ( 3 ) Class B Common Stock ( 5 ) ( 5 ) ( 5 )( 6 ) ( 5 ) Common Stock 900,848 I See Footnotes ( 2 ) ( 3 ) ( 4 ) Pre-Funded Warrants ( 7 ) $ 0.0001 ( 8 )( 9 ) ( 7 ) Common Stock 945,547 I See Footnotes ( 1 ) ( 2 ) ( 3 ) Pre-Funded Warrants ( 7 ) $ 0.0001 ( 8 )( 9 ) ( 7 ) Common Stock 10,304,453 I See Footnotes ( 2 ) ( 3 ) ( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other BAKER BROS. ADVISORS LP 860 WASHINGTON STREET, 3RD FLOOR NEW YORK, NY10014 X Baker Bros. Advisors (GP) LLC 860 WASHINGTON STREET, 3RD FLOOR NEW YORK, NY10014 X BAKER FELIX 860 WASHINGTON STREET, 3RD FLOOR NEW YORK, NY10014 X BAKER JULIAN 860 WASHINGTON STREET, 3RD FLOOR NEW YORK, NY10014 X Signatures By: Baker Bros. Advisors LP, Name: Scott L. Lessing, Title: President /s/ Scott L. Lessing 02/14/2025 Signature of Reporting Person Date By: Baker Bros. Advisors (GP) LLC, Name: Scott L. Lessing, Title: President /s/ Scott L. Lessing 02/14/2025 Signature of Reporting Person Date /s/ Felix J. Baker 02/14/2025 Signature of Reporting Person Date /s/ Julian C. Baker 02/14/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )As a result of their ownership interest in (i) Baker Biotech Capital, L.P. and (ii) 667, L.P. ("667") Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in Class A common stock ("Common Stock") of Sera Prognostics, Inc. (the "Issuer") reported in column 2 of Table I and securities of the Issuer reported in column 3 of Table II held directly by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to their interest in 667 and Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667. ( 2 )Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to 667 and Baker Brothers Life Sciences, L.P. ("Life Sciences" and together with 667, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held directly by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held directly by the Funds or for the benefit of the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held directly by the Funds. ( 3 )Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose. ( 4 )As a result of their ownership interest in (i) Baker Brothers Life Sciences Capital, L.P. and (ii) Life Sciences, Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in Common Stock reported in column 2 of Table I and the securities of the Issuer reported in column 3 of Table II held directly by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to their interest in Life Sciences and Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences. ( 5 )These securities consist of Class B non-voting common stock of the Issuer ("Class B Common Stock") which are convertible at any time on a 1-for-1 basis without payment or further consideration into Common Stock, subject to a 4.99% beneficial ownership limitation described below. The Class B Common Stock is only convertible to the extent that immediately prior to or as a result of such conversion the holders thereof together with their affiliates and any persons who are members of a Section 13(d) group with the holders or their affiliates would beneficially own in the aggregate, for purposes of Rule 13d-3 under the Exchange Act, no more than 4.99% of the outstanding Common Stock after conversion (the "Class B Beneficial Ownership Limitation"). The Class B Common Stock has no expiration date. ( 6 )By written notice to the Issuer, the Funds may increase or decrease the Class B Beneficial Ownership Limitation applicable to that fund to any other percentage not in excess of 19.99%; provided that any such increase will not be effective until the 61st day after such notice is delivered to the Issuer. ( 7 )These securi ties consist of warrants to purchase Common Stock at an exercise price of $0.0001 per share with no expiration date ("Pre-Funded Warrants"). ( 8 )The Pre-Funded Warrants are exercisable at any time, at the holder's election, on a 1-for-1 basis into Common Stock to the extent that immediately prior to or after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage"). ( 9 )By written notice to the Issuer, the Funds may increase or decrease the Maximum Percentage applicable to that fund to any other percentage not in excess of 19.99%; provided that any such increase will not be effective until the 61st day after such notice is delivered to the Issuer.

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