Lyell CMO sells 500 shares at $12.70 each

Rhea-AI Filing Summary

Lyell Immunopharma, Inc. (LYEL) reported that Chief Medical Officer David Shook sold 500 shares of common stock on September 10, 2026 in an open-market transaction primarily to cover a tax withholding obligation from the settlement of vested restricted stock units. The shares were sold at a weighted average price of $12.70 per share, within a range of $12.32 to $12.70 per share. After this sale, Shook directly holds 20,423 shares of Lyell common stock, and no Rule 10b5-1 trading plan is reported for this transaction.

Insider Trade Summary

Net Seller: 500 shares

Net Sell 1 txn

Insider Shook David

Role Chief Medical Officer

Sold 500 shs ($6K)

Type	Security	Shares	Price	Value
Sale	Common Stock F1, F2	500	$12.70	$6K

Holdings After Transaction: Common Stock — 20,423 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 $12.32 to $12.70 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

Shares sold: 500 shares Weighted average sale price: $12.70 per share Shares held after transaction: 20,423 shares

3 metrics

Shares sold 500 shares Common stock sale by Chief Medical Officer on September 10, 2026

Weighted average sale price $12.70 per share Weighted average price for the 500 shares sold; prices ranged from $12.32 to $12.70

Shares held after transaction 20,423 shares Directly owned by David Shook after the September 10, 2026 sale

Key Terms

restricted stock units, tax withholding obligation, weighted average price

3 terms

restricted stock units financial

"from 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.

tax withholding obligation financial

"sold to cover tax withholding obligation from settlement"

weighted average price financial

"The price reported above reflects the weighted average price"

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.

FAQ

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

What insider transaction did Lyell Immunopharma (LYEL) disclose for David Shook?

Lyell disclosed that Chief Medical Officer David Shook sold 500 shares of common stock on September 10, 2026. The sale was primarily to cover a tax withholding obligation arising from the settlement of vested restricted stock units.

At what price were the LYEL shares sold in this Form 4 transaction?

The 500 LYEL shares were sold at a weighted average price of $12.70 per share. The filing states the sale prices ranged from $12.32 to $12.70 per share, and detailed breakdowns are available upon request to the company, the SEC staff, or a security holder.

How many LYEL shares does David Shook hold after this reported sale?

After the reported sale, Chief Medical Officer David Shook directly holds 20,423 shares of Lyell Immunopharma common stock. This post-transaction balance is explicitly stated in the Form 4 data.

Was the LYEL insider sale by David Shook made under a Rule 10b5-1 trading plan?

No. The filing indicates the Rule 10b5-1 checkbox is not affirmed, and there is no footnote stating that the sale was made pursuant to a Rule 10b5-1 or other pre-arranged trading plan.

Why did David Shook sell LYEL shares according to the Form 4 footnotes?

A footnote explains that the shares were automatically sold to cover tax withholding obligations arising from the settlement of vested restricted stock units, indicating the sale was tied to equity compensation vesting rather than a discretionary portfolio trade.

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

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Available on EDGAR 09/10/2026 - 07:38 PM Accepted by SEC EDGAR 09/10/2026 - 07:37 PM 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^*

Shook David

(Last) (First) (Middle)

C/O LYELL IMMUNOPHARMA, INC.

201 HASKINS WAY, SUITE 101

(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)
09/10/2026

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	09/10/2026		S		500(1)	D	$12.7(2)	20,423	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 $12.32 to $12.70 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	09/10/2026
	** 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)