Sutro Biopharma (STRO) director awarded 10,000 stock options at $26.09 strike

Rhea-AI Filing Summary

Sutro Biopharma director James P. Panek received a grant of stock options covering 10,000 shares of common stock. The options have an exercise price of $26.09 per share and expire on June 5, 2036. They vest 8.33% monthly starting July 5, 2026 and are fully exercisable by the earlier of the 2027 annual stockholders meeting or June 5, 2027, assuming continued service.

Insights

Equity compensation analyst

Routine director stock option grant with time-based vesting.

James P. Panek, a director of Sutro Biopharma, was granted options for 10,000 shares of common stock at an exercise price of $26.09 per share, expiring on June 5, 2036. This is characterized as a grant or award, not an open-market purchase.

The award vests in equal monthly installments of 8.33% of the total grant, beginning on July 5, 2026, and becomes fully vested by the earlier of the company’s 2027 annual stockholders meeting or June 5, 2027, contingent on continued service. No sales or exercises are reported in this filing.

This looks like standard board compensation using stock options to align director incentives with long-term shareholder value. The filing does not show other derivative positions, so this 10,000-share option grant represents the derivative position visible from this report alone.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider PANEK JAMES P

Role null

Type	Security	Shares	Price	Value
Grant/Award	Stock Option (right to buy)	10,000	$0.00	--

Holdings After Transaction: Stock Option (right to buy) — 10,000 shares (Direct, null)

Footnotes (1)

1. [object Object]

Key Figures

Option grant size: 10,000 shares Exercise price: $26.09 per share Expiration date: June 5, 2036 +3 more

6 metrics

Option grant size 10,000 shares Stock option award to director James P. Panek

Exercise price $26.09 per share Stock option strike price

Expiration date June 5, 2036 Option expiration

Vesting rate 8.33% monthly Portion of award vesting each month

First vesting date July 5, 2026 Initial vesting tranche

Full vesting deadline Earlier of 2027 meeting or June 5, 2027 Date grant becomes fully exercisable

Key Terms

Stock Option (right to buy), exercise price, vesting, fully vested and exercisable, +1 more

5 terms

Stock Option (right to buy) financial

"security_title: "Stock Option (right to buy)""

exercise price financial

"conversion_or_exercise_price: "26.0900""

The exercise price is the fixed amount at which you can buy or sell an asset, like a stock, when using an options contract. It matters because it helps determine whether exercising the option will be profitable or not, depending on the current market price. Think of it as the set price you agree on today to buy or sell later.

vesting financial

"The option shall vest, subject to the reporting person's provision of service"

Vesting is the process by which you earn full ownership of something, like company stock or a retirement benefit, over time. It’s like earning the right to keep a gift piece by piece the longer you stay with a company, making sure employees stay committed before they receive all the benefits.

fully vested and exercisable financial

"the award shall be fully vested and exercisable on the earlier of"

annual stockholders meeting financial

"the issuer's 2027 annual stockholders meeting"

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Form 4 Insider Transactions: What Each Field Means →

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^*

PANEK JAMES P

(Last) (First) (Middle)

C/O SUTRO BIOPHARMA, INC.

111 OYSTER POINT BLVD.

(Street)

SOUTH SAN FRANCISCO CALIFORNIA 94080

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
SUTRO BIOPHARMA, INC. [ STRO ]

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

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
06/05/2026

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

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
Stock Option (right to buy)	$26.09	06/05/2026		A		10,000		(1)	06/05/2036	Common Stock	10,000	$0	10,000	D

Explanation of Responses:

1. The option shall vest, subject to the reporting person's provision of service to the issuer on each vesting date, as to 8.33% of the total award monthly, with the first tranche vesting on July 5, 2026, and the award shall be fully vested and exercisable on the earlier of (i) the date of the issuer's 2027 annual stockholders meeting or (ii) June 5, 2027.

	/s/ David Pauling as attorney-in-fact	06/09/2026
	** 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)

FAQ

What did Sutro Biopharma (STRO) director James P. Panek receive in this Form 4?

James P. Panek received a stock option grant for 10,000 shares of Sutro Biopharma common stock. The options are a compensation award, not an open-market purchase, and give him the right to buy shares at a fixed exercise price in the future.

What is the exercise price and expiration date of the new STRO stock options?

The granted options have an exercise price of $26.09 per share and expire on June 5, 2036. This means Panek can choose to buy up to 10,000 shares at $26.09 before the June 5, 2036 expiration, once the options are vested.

How do the James P. Panek stock options in Sutro Biopharma vest?

The options vest in equal monthly installments of 8.33% of the 10,000-share award. Vesting starts on July 5, 2026 and the grant becomes fully vested and exercisable by the earlier of Sutro’s 2027 annual stockholders meeting or June 5, 2027, assuming continued service.

Is the Form 4 for STRO an insider purchase or a compensation award?

The Form 4 reflects a compensation award, not an open-market purchase. The transaction code is “A” for a grant or award acquisition of stock options, giving James P. Panek rights to buy shares in the future rather than reporting immediate buying or selling in the open market.

How many Sutro Biopharma shares are covered by James P. Panek’s new options?

The stock option grant covers 10,000 shares of Sutro Biopharma common stock. After this grant, the Form 4 shows total derivative holdings of 10,000 options from this award, with no additional option positions disclosed in the filing’s derivative summary section.

When will James P. Panek’s STRO option grant be fully exercisable?

The option grant will be fully vested and exercisable on the earlier of Sutro Biopharma’s 2027 annual stockholders meeting or June 5, 2027. This full vesting depends on Panek continuing to provide service to the company through the applicable vesting dates.