Sutro Biopharma (STRO) CFO exercises 2,500 RSUs and increases direct holdings

Rhea-AI Filing Summary

Sutro Biopharma CFO Gregory K. Chow exercised equity awards and increased his direct stake in the company. On June 2, 2026, he exercised Restricted Stock Units (RSUs) covering 2,500 shares of Common Stock, with no shares sold in this filing. Following the transaction, he directly holds 4,725 shares of Common Stock and 7,500 RSUs, each representing the right to receive one share upon settlement. Footnotes state that tax withholding obligations were satisfied in cash rather than by withholding shares, and that his total Common Stock holdings include 250 shares acquired under the company’s employee stock purchase plan.

Insights

Equity compensation analyst

CFO exercised RSUs to acquire shares with no sale activity.

The CFO of Sutro Biopharma, Gregory K. Chow, exercised RSUs covering 2,500 shares of Common Stock. This is a compensation-related derivative exercise, not an open-market purchase, and there are no reported stock sales in this filing.

After the exercise, he directly holds 4,725 Common Shares and 7,500 RSUs, each RSU convertible into one share upon settlement. Footnotes clarify that tax liabilities from vesting were paid in cash, so no shares were withheld for taxes.

This pattern is typical for executive equity compensation. It increases the CFO’s direct share ownership while preserving remaining RSUs that vest over time, aligning part of his compensation with Sutro Biopharma’s future stock performance.

Insider Trade Summary

2,500 shares exercised/converted

Mixed 2 txns

Insider Chow Gregory K.

Role CFO

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units (RSUs)	2,500	$0.00	--
Exercise	Common Stock	2,500	$0.00	--

Holdings After Transaction: Restricted Stock Units (RSUs) — 7,500 shares (Direct, null); Common Stock — 4,725 shares (Direct, null)

Footnotes (1)

1. For avoidance of doubt, the reporting person elected to satisfy tax withholding liabilities in cash in lieu of withholding shares. The reported total includes 250 shares of Common Stock acquired by the reporting person in one or more transactions with the Issuer pursuant to its employee stock purchase plan, which transactions are exempt pursuant to Rules 16a3(f)(1)(i)(B) and 16b3(c). Each RSU represents a contingent right to receive one (1) share of the Issuer's Common Stock upon settlement. The award vested or vests annually as to 1/4th of the total award, subject to the reporting person's continued service to the Issuer on each vesting date, with the first tranche vested on June 2, 2026.

Key Figures

RSUs exercised: 2,500 shares Common Stock held after: 4,725 shares RSUs held after: 7,500 RSUs +2 more

5 metrics

RSUs exercised 2,500 shares RSUs converted into Common Stock on June 2, 2026

Common Stock held after 4,725 shares Direct Common Stock holdings following the reported transactions

RSUs held after 7,500 RSUs Total Restricted Stock Units remaining after the transaction

RSU expiration June 2, 2029 Expiration date for the RSU award reported as a derivative security

ESPP shares included 250 shares Common Stock acquired via employee stock purchase plan included in total

Key Terms

Restricted Stock Units (RSUs), employee stock purchase plan, tax withholding liabilities, contingent right, +1 more

5 terms

Restricted Stock Units (RSUs) financial

"Restricted Stock Units (RSUs) ... Each RSU represents a contingent right to receive one (1) share"

Restricted stock units (RSUs) are a type of company promise to give employees shares of stock in the future, usually after certain conditions like working for a set time. They are like a gift promised today that you receive later, which can become valuable if the company's stock price goes up. RSUs matter because they are a way companies reward employees and can be a significant part of compensation.

employee stock purchase plan financial

"shares of Common Stock acquired ... pursuant to its employee stock purchase plan"

An employee stock purchase plan is a company program that lets workers buy shares through small payroll deductions, often at a discount to the market price and after a set offering period. Think of it like a workplace savings plan that turns into ownership: it encourages employees to share in the company’s success and can create predictable buying or selling of stock that investors watch because it affects supply, demand and employee incentives.

tax withholding liabilities financial

"elected to satisfy tax withholding liabilities in cash in lieu of withholding shares"

contingent right financial

"Each RSU represents a contingent right to receive one (1) share"

vested or vests annually financial

"The award vested or vests annually as to 1/4th of the total award"

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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^*

Chow Gregory K.

(Last) (First) (Middle)

C/O SUTRO BIOPHARMA, INC.

111 OYSTER POINT BOULEVARD

(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)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
06/02/2026

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	06/02/2026		M		2,500(1)	A	$0	4,725(2)	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
Restricted Stock Units (RSUs)	(3)	06/02/2026		M			2,500	(4)	06/02/2029	Common Stock	2,500	$0	7,500	D

Explanation of Responses:

1. For avoidance of doubt, the reporting person elected to satisfy tax withholding liabilities in cash in lieu of withholding shares.

2. The reported total includes 250 shares of Common Stock acquired by the reporting person in one or more transactions with the Issuer pursuant to its employee stock purchase plan, which transactions are exempt pursuant to Rules 16a3(f)(1)(i)(B) and 16b3(c).

3. Each RSU represents a contingent right to receive one (1) share of the Issuer's Common Stock upon settlement.

4. The award vested or vests annually as to 1/4th of the total award, subject to the reporting person's continued service to the Issuer on each vesting date, with the first tranche vested on June 2, 2026.

	/s/ David Pauling as attorney-in-fact	06/02/2026
	** 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) CFO Gregory K. Chow report in this Form 4?

He reported exercising RSU awards into 2,500 shares of Common Stock. The filing shows a compensation-related derivative exercise, with no open-market stock purchases or sales disclosed in these transactions.

How many Sutro Biopharma (STRO) shares does the CFO hold after this Form 4?

After the reported transactions, the CFO directly holds 4,725 shares of Common Stock. He also holds 7,500 Restricted Stock Units (RSUs), each representing a right to receive one share upon settlement in the future.

Did the Sutro Biopharma (STRO) CFO sell any shares in this Form 4 filing?

No shares were sold in the reported transactions. The Form 4 only shows RSU exercises that increased his share ownership, with tax obligations satisfied in cash rather than through share withholding.

What are the RSUs reported by Sutro Biopharma (STRO) CFO Gregory K. Chow?

The RSUs are equity awards where each unit represents a contingent right to receive one share of Sutro Biopharma Common Stock. They vest over time, subject to his continued service to the company on each vesting date.

How were taxes handled on the Sutro Biopharma (STRO) CFO’s RSU vesting?

Footnotes state the CFO chose to pay tax withholding liabilities in cash. This means no shares were withheld to cover taxes, so all RSU shares from this vesting were retained.

What additional Sutro Biopharma (STRO) shares are included in the CFO’s total holdings?

His total Common Stock holdings include 250 shares acquired through Sutro Biopharma’s employee stock purchase plan. These plan purchases are described as exempt under specific SEC rules in the footnotes.