Lyell Immunopharma medical chief sells 422 shares

Lyell Immunopharma, Inc. Chief Medical Officer Jarrad Mattieu Aguirre reported an automatic sale of 422 common shares on October 12, 2026, to cover tax withholding from the settlement of vested restricted stock units.

Rhea-AI Filing Summary

Lyell Immunopharma, Inc. Chief Medical Officer Jarrad Mattieu Aguirre reported an automatic sale of 422 common shares on October 12, 2026, to cover tax withholding from the settlement of vested restricted stock units. The shares sold at a weighted average price of $8.63 per share, within a range of $8.54 to $8.63. He directly held 19,857 shares afterward.

Insider Trade Summary

Net Seller: 422 shares

Net Sell 1 txn

Insider Aguirre Jarrad Mattieu

Role Chief Medical Officer

Sold 422 shs ($4K)

Type	Security	Shares	Price	Value
Sale	Common Stock F1, F2	422	$8.63	$4K

Holdings After Transaction: Common Stock — 19,857 shares (Direct)

Footnotes (2)

1. F1. Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.
2. F2. The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $8.54 to $8.63 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Key Figures

Common shares sold: 422 shares Weighted average sale price: $8.63 per share Sale price range: $8.54 to $8.63 per share +1 more

4 metrics

Common shares sold 422 shares Automatically sold October 12, 2026, to cover tax withholding from settlement of vested restricted stock units

Weighted average sale price $8.63 per share Weighted average price of shares sold

Sale price range $8.54 to $8.63 per share Price range for the shares sold

Shares held after transaction 19,857 shares Directly held after the sale

Key Terms

restricted stock units, weighted average price, tax withholding obligation

3 terms

restricted stock units technical

"settlement of vested restricted stock units"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

weighted average price financial

"reflects the weighted average price of the shares sold"

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

tax withholding obligation financial

"cover tax withholding obligation from settlement"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many LYEL shares did the chief medical officer sell, and at what price?

Jarrad Mattieu Aguirre's 422 shares were automatically sold on October 12, 2026, at a weighted average of $8.63 per share to cover tax withholding from settlement of vested restricted stock units; sale prices ranged from $8.54 to $8.63 per share.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 10/13/2026 - 05:18 PM EDT Accepted by SEC EDGAR 10/13/2026 - 05:17 PM EDT Learn about SEC filing dates

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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 for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Aguirre Jarrad Mattieu

(Last) (First) (Middle)

C/O LYELL IMMUNOPHARMA, INC.

201 HASKINS WAY

(Street)

SOUTH SAN FRANCISCO CALIFORNIA 94080

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Lyell Immunopharma, Inc. [ LYEL ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Medical Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/12/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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	10/12/2026		S		422(1)	D	$8.63(2)	19,857	D

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 Securities Underlying Derivative Security (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: 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

Explanation of Responses:

1. Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

2. The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $8.54 to $8.63 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

	/s/ Mark Meltz, Attorney-in-Fact	10/13/2026
	** Signature of Reporting Person	Date
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).
** 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.
* Form 4: SEC 1474 (03-26)