Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 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 (Month/Day/Year) 03/06/2026 (Street) CHICAGO, IL 60631 4. If Amendment, Date Original Filed (Month/Day/Year) 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 (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 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 03/06/2026 P 488,090 A $25.61 1,426,528 I See footnote(1) Common Stock 910,317 I See footnote(2) Common Stock 910,317 I See footnote(3)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

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 (Month/Day/Year)

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, IL 60631		X
ARCH Venture Partners XIII, L.P. 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL 60631		X
ARCH Venture Partners XIII, LLC 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL 60631		X
CRANDELL KEITH 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL 60631		X
NELSEN ROBERT 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL 60631		X
Burow Kristina 8755 W. HIGGINS ROAD,SUITE 1025 CHICAGO, IL 60631		X
GILLIS STEVEN 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO, IL 60631		X
BERNS PAUL L 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL 60631		X
BYBEE CLINTON 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL 60631		X

Signatures

ARCH Venture Partners XIII, LLC, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director		03/09/2026
**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		03/09/2026
**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		03/09/2026
**Signature of Reporting Person		Date
Keith Crandell, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact		03/09/2026
**Signature of Reporting Person		Date
Robert Nelsen, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact		03/09/2026
**Signature of Reporting Person		Date
Kristina Burow, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact		03/09/2026
**Signature of Reporting Person		Date
Steven Gillis, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact		03/09/2026
**Signature of Reporting Person		Date
Paul Berns, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact		03/09/2026
**Signature of Reporting Person		Date
Clinton Bybee, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact		03/09/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	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.
(2)	These shares are directly held by ARCH Venture Fund IX, L.P. ("ARCH IX"). ARCH Venture Partners IX, L.P. ("GPLP"), as the sole general partner of ARCH IX, may be deemed to beneficially own the shares held by ARCH IX. ARCH Venture Partners IX, LLC ("GPLLC"), as the sole general partner of GPLP, may be deemed to beneficially own the shares held by ARCH IX. As managing directors of GPLLC, each of Keith Crandell, Robert Nelsen and Clinton Bybee (the "ARCH Managing Directors"), may be deemed to beneficially own the shares held by ARCH IX. Each of GPLP, GPLLC and the ARCH Managing Directors disclaims beneficial ownership of the securities reported herein, except to the extent of their pecuniary interest therein, if any.
(3)	These shares are directly held by ARCH Venture Fund IX Overage, L.P. ("ARCH Overage"). ARCH Venture Partners IX Overage, L.P. ("Overage GPLP"), as the sole general partner of ARCH Overage, may be deemed to beneficially own the shares held by ARCH Overage. GPLLC, as the sole general partner of Overage GPLP, may be deemed to beneficially own the shares held by ARCH Overage. As managing directors of GPLLC, each of the ARCH Managing Directors may be deemed to beneficially own the shares held by ARCH Overage. Each of Overage GPLP, GPLLC and the ARCH Managing Directors disclaims beneficial ownership of the securities reported herein, except to the extent of their pecuniary interest therein, if any.
Remarks: This Form 4 is one of two reports relating to the same transaction being filed jointly by ARCH Venture Partners XIII, LLC, ARCH Venture Partners XIII, L.P., ARCH Venture Fund XIII, L.P., Keith Crandell, Robert Nelsen, Kristina Burow, Steven Gillis, Paul Berns, Clinton Bybee, ARCH Venture Partners IX, LLC, ARCH Venture Partners IX, L.P., ARCH Venture Partners IX Overage, L.P., ARCH Venture Fund IX, L.P. and ARCH Venture Fund IX Overage, L.P.

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