SEC FORM 3SEC Form 3
FORM 3UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF 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*
Aguirre Jarrad Mattieu

(Last)(First)(Middle)
C/O LYELL IMMUNOPHARMA, INC.
201 HASKINS WAY

(Street)
SOUTH SAN FRANCISCOCA94080

(City)(State)(Zip)
2. Date of Event Requiring Statement (Month/Day/Year)
08/31/2026
3. Issuer Name and Ticker or Trading Symbol
Lyell Immunopharma, Inc. [ LYEL ]
Foreign Trading Symbol
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
Director10% Owner
checkbox checkedOfficer (give title below)Other (specify below)
Chief Medical Officer
5. If Amendment, Date of Original Filed (Month/Day/Year)
6. Individual or Joint/Group Filing (Check Applicable Line)
checkbox checkedForm filed by One Reporting Person
Form filed by More than One Reporting Person
Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock20,279(1)D
Table II - Derivative Securities Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4) 2. Date Exercisable and Expiration Date (Month/Day/Year)3. Title and Amount of Securities Underlying Derivative Security (Instr. 4) 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 6. Nature of Indirect Beneficial Ownership (Instr. 5)
Date ExercisableExpiration DateTitleAmount or Number of Shares
Option (right to buy) (2)02/12/2035Common Stock46,24911.64D
Option (right to buy) (3)02/09/2036Common Stock35,00023.71D
Option (right to buy) (4)05/10/2036Common Stock15,00019.2D
Explanation of Responses:
1. Includes 14,451 restricted stock units ("RSUs") under the Issuer's 2021 Equity Incentive Plan that are subject to time-based vesting and will be settled in common stock subject to vesting as follows: the RSUs vest quarterly over the thirty month period following July 9, 2026; in each case, subject to the reporting person providing service through the applicable vesting date.
2. 25% of the option shares vested on January 31, 2026, with the remaining option shares to vest in equal monthly installments over the following thirty-six months, subject to the reporting person providing service through the applicable vesting date.
3. 12.5% of the option shares will vest on August 9, 2026, with the remaining option shares to vest in equal monthly installments over the following forty-two months, subject to the reporting person providing service through the applicable vesting date.
4. 12.5% of the option shares will vest on November 11, 2026, with the remaining option shares to vest in equal monthly installments over the following forty-two months, subject to the reporting person providing service through the applicable vesting date.
/s/ Mark Meltz, Attorney-in-Fact09/10/2026
** Signature of Reporting PersonDate
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 5 (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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
ex24-09102026_110902.htm

POWER OF ATTORNEY


(For Executing Forms 3, 4 and 5)


Know all by these presents, that the undersigned hereby constitutes and appoints each of Lynn Seely, Smital Shah and Mark Meltz of Lyell Immunopharma, Inc. (the “Company”), or any of them signing singly, with full power of substitution, the undersigned’s true and lawful attorneys-in-fact and agents to:

(1)

prepare, execute for and on behalf of the undersigned, in the undersigned’s capacity as an officer, director or beneficial owner of more than 10% of a registered class of securities of the Company, Forms 3, 4 and 5 (including any amendments thereto) in accordance with Section 16(a) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and the rules thereunder and a Form ID, Uniform Application for Access Codes to File on EDGAR;

(2)

do and perform any and all acts for and on behalf of the undersigned that may be necessary or desirable to execute such Forms 3, 4 or 5 or Form ID (including any amendments thereto) and timely file such forms with the United States Securities and Exchange Commission and any stock exchange or similar authority; and

(3)

take any other action of any nature whatsoever in connection with the foregoing which, in the opinion of such attorney-in-fact, may be of benefit, in the best interest of, or legally required by, the undersigned, it being understood that the documents executed by such attorney-in-fact on behalf of the undersigned pursuant to this Power of Attorney shall be in such form and shall contain such terms and conditions as such attorney-in-fact may approve in such attorney-in-fact’s discretion.

The undersigned hereby grants to each such attorney-in-fact full power and authority to do and perform any and every act and thing whatsoever requisite, necessary or proper to be done in the exercise of any of the rights and powers herein granted, as fully to all intents and purposes as the undersigned might or could do if personally present, with full power of substitution or revocation, hereby ratifying and confirming all that such attorney-in-fact, or such attorney-in-fact’s substitute or substitutes, shall lawfully do or cause to be done by virtue of this power of attorney and the rights and powers herein granted.  The undersigned acknowledges that the foregoing attorneys-in-fact, in serving in such capacity at the request of the undersigned, are not assuming, nor is the Company assuming, any of the undersigned’s responsibilities to comply with Section 16 of the Exchange Act.

This Power of Attorney shall remain in full force and effect until the earliest to occur of (a) the undersigned is no longer required to file Forms 3, 4 and 5 with respect to the undersigned’s holdings of and transactions in securities issued by the Company, (b) revocation by the undersigned in a signed writing delivered to the foregoing attorneys-in-fact or (c) as to any attorney-in-fact individually, until such attorney-in-fact is no longer employed by the Company or Cooley LLP.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of this 7th day of August, 2026.


/s/ Jarrad Mattieu Aguirre

Jarrad Mattieu Aguirre, M.D., M.B.A.




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