Sec Form 4 Filing - Frazier Life Sciences X, L.P. @ HilleVax, Inc. - 2025-09-17

FORM 4 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 Frazier Life Sciences X, L.P. 2. Issuer Name and Ticker or Trading Symbol HilleVax, Inc. [ HLVX] 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) FRAZIER LIFE SCIENCES MANAGEMENT, L.P., 1001 PAGE MILL RD, BUILDING 4, SUITE B 3. Date of Earliest Transaction (MM/DD/YY) 09/17/2025 (Street) PALO ALTO, CA94304 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 09/17/2025 U 8,535,337 D $ 1.95 ( 1 ) 0 I By Frazier Life Sciences X, L.P. ( 2 ) Common Stock 09/17/2025 U 17,199 D $ 1.95 ( 3 ) 0 I By Patrick J. Heron

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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Frazier Life Sciences X, L.P. FRAZIER LIFE SCIENCES MANAGEMENT, L.P. 1001 PAGE MILL RD, BUILDING 4, SUITE B PALO ALTO, CA94304 X FHMLS X, L.P. FRAZIER LIFE SCIENCES MANAGEMENT, L.P. 1001 PAGE MILL RD, BUILDING 4, SUITE B PALO ALTO, CA94304 X FHMLS X, L.L.C. FRAZIER LIFE SCIENCES MANAGEMENT, L.P. 1001 PAGE MILL RD, BUILDING 4, SUITE B PALO ALTO, CA94304 X Topper James N FRAZIER LIFE SCIENCES MANAGEMENT, L.P. 1001 PAGE MILL RD, BUILDING 4, SUITE B PALO ALTO, CA94304 X Heron Patrick J FRAZIER LIFE SCIENCES MANAGEMENT, L.P. 1001 PAGE MILL RD, BUILDING 4, SUITE B PALO ALTO, CA94304 X X Signatures /s/ Steve R. Bailey, CFO of FHMLS X, L.L.C., GP of FHMLS X, L.P., GP of Frazier Life Sciences X, L.P. 09/17/2025 Signature of Reporting Person Date /s/ Steve R. Bailey, CFO of FHMLS X, L.L.C., GP of FHMLS X, L.P. 09/17/2025 Signature of Reporting Person Date /s/ Steve R. Bailey, CFO of FHMLS X, L.L.C. 09/17/2025 Signature of Reporting Person Date /s/ Steve R. Bailey, Attorney-in-Fact For Patrick J. Heron 09/17/2025 Signature of Reporting Person Date /s/ Steve R. Bailey, Attorney-in-Fact For James N. Topper 09/17/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Reflects disposition of the Issuer's equity securities upon the consummation of the transactions contemplated by the Agreement and Plan of Merger (the "Merger Agreement"), dated as of August 4, 2025, by and among Issuer, XOMA Royalty Corporation ("Parent") and XRA 4 Corp., a wholly owned subsidiary of Parent ("Merger Sub"), including the consummation of the merger (the "Merger") between Issuer and Merger Sub on September 17, 2025. Pursuant to the Merger Agreement, as of the effective time of the Merger (the "Effective Time"), each share of the Issuer's Common Stock, par value $0.0001 per share ("Shares"), issued and outstanding immediately prior to the Effective Time was converted automatically into the right to receive (i) $1.95 in cash, without interest plus (ii) one non-transferable contractual contingent value right per Share. ( 2 )The shares are held directly by Frazier Life Sciences X, L.P. FHMLS X,, L.P. is the general partner of Frazier Life Sciences X, L.P. and FHMLS X, L.L.C. is the general partner of FHMLS X, L.P. James N. Topper and Patrick J. Heron are the sole managing members of FHMLS X, L.L.C. and share voting and investment power over the shares held by Frazier Life Sciences X, L.P. Dr. Topper and Mr. Heron disclaim beneficial ownership of such securities except to the extent of their pecuniary interest therein. ( 3 )Pursuant to the terms of the Merger Agreement, immediately prior to the Effective Time, each outstanding restricted stock unit ("RSU") immediately vested in full and was canceled in exchange for the right receive (a) an amount in cash, without interest, equal to the product obtained by multiplying (x) the $1.95 by (y) the number of shares underlying such RSU at the Effective Time and (b) one CVR for each share underlying such RSU.

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).

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