Sec Form 3 Filing - ARCH Venture Fund XIII, L.P. @ Lyell Immunopharma, Inc. - 2025-07-25

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 ARCH Venture Fund XIII, L.P. 2. Issuer Name and Ticker or Trading Symbol Lyell Immunopharma, Inc. [ LYEL] 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) 8755 W. HIGGINS ROAD, SUITE 1025, 3. Date of Earliest Transaction (MM/DD/YY) 07/25/2025 (Street) CHICAGO, IL60631 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 938,438 ( 1 ) I By: ARCH Venture Fund XIII, L.P. ( 2 )

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 ARCH Venture Fund XIII, L.P. 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X ARCH Venture Partners XIII, L.P. 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X ARCH Venture Partners XIII, LLC 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X CRANDELL KEITH C/O ARCH VENTURE PARTNERS IX, LLC 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X NELSEN ROBERT 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X Burow Kristina 8755 W. HIGGINS ROAD,SUITE 1025 CHICAGO, IL60631 X GILLIS STEVEN C/O ARCH VENTURE PARTNERS 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X BERNS PAUL L 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X Signatures ARCH Venture Partners XIII, LLC, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director 07/29/2025 Signature of Reporting Person Date ARCH Venture Partners XIII, L.P., By: ARCH Venture Partners XIII, LLC, its General Partner, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director 07/29/2025 Signature of Reporting Person Date ARCH Venture Fund XIII, L.P., By: ARCH Venture Partners XIII, L.P., its General Partner, By: ARCH Venture Partners XIII, LLC, its General Partner, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director 07/29/2025 Signature of Reporting Person Date Keith Crandell, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact 07/29/2025 Signature of Reporting Person Date Robert Nelsen, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact 07/29/2025 Signature of Reporting Person Date Kristina Burow, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact 07/29/2025 Signature of Reporting Person Date Steven Gillis, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact 07/29/2025 Signature of Reporting Person Date Paul Berns, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact 07/29/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )These shares were purchased on July 25, 2025 pursuant to a securities purchase agreement dated July 24, 2025 at a price per share of $13.32. ( 2 )These shares are directly held by ARCH Venture Fund XIII, L.P. ("ARCH XIII"). ARCH Venture Partners XIII, L.P. ("AVP XIII LP") is the general partner of ARCH XIII. ARCH Venture Partners XIII, LLC ("AVP XIII LLC") is the general partner of AVP XIII LP. Keith Crandell, Robert Nelsen, Kristina Burow, Paul Berns and Steven Gillis are members of the investment committee of AVP XIII LLC (the "AVP XIII LLC Committee Members"). Each of AVP XIII LP and AVP XIII LLC may be deemed to beneficially own the shares held by ARCH XIII, and each of the AVP XIII LLC Committee Members may be deemed to share the power to direct the disposition and vote of the shares held by ARCH XIII. Each of AVP XIII LP, AVP XIII LLC and the AVP XIII LLC Committee Members disclaims beneficial ownership except to the extent of their pecuniary interest therein, if any.

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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