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Sutro Biopharma (NASDAQ: STRO) CSO receives RSUs and options

Filing Impact
(Neutral)
Filing Sentiment
(Neutral)
Form Type
4

Rhea-AI Filing Summary

Sutro Biopharma Chief Scientific Officer Hans-Peter Gerber reported multiple equity transactions involving restricted stock units (RSUs), stock options and common shares. On March 1 and 2, 2026, RSU vesting led to the acquisition of 1,125 and 2,843 shares of common stock through derivative exercises at a stated price of $0.00 per share.

To cover income tax withholding obligations related to these RSU settlements, the issuer withheld 463 and 1,170 shares of common stock at prices of $20.47 and $20.55 per share, which the footnotes clarify do not represent sales by the reporting person. Gerber also received direct grants of 5,000 RSUs and a stock option for 40,000 shares, each subject to time-based vesting schedules described in the footnotes, including annual RSU vesting in four tranches and a stock option that vests in 1/48 monthly installments beginning on April 1, 2026.

Positive

  • None.

Negative

  • None.
Insider Gerber Hans-Peter
Role CHIEF SCIENTIFIC OFFICER
Type Security Shares Price Value
Exercise Restricted Stock Units (RSUs) 2,843 $0.00 --
Grant/Award Restricted Stock Units (RSUs) 5,000 $0.00 --
Grant/Award Stock Option (right to buy) 40,000 $0.00 --
Exercise Common Stock 2,843 $0.00 --
Tax Withholding Common Stock 1,170 $20.55 $24K
Exercise Restricted Stock Units (RSUs) 1,125 $0.00 --
Exercise Common Stock 1,125 $0.00 --
Tax Withholding Common Stock 463 $20.47 $9K
Holdings After Transaction: Restricted Stock Units (RSUs) — 8,532 shares (Direct); Stock Option (right to buy) — 40,000 shares (Direct); Common Stock — 10,688 shares (Direct)
Footnotes (1)
  1. Represents the number of shares of Common Stock that have been withheld by the Issuer to satisfy its income tax withholding and remittance obligations in connection with the net settlement of restricted stock units; does not represent a sale by the reporting person. Each RSU represents a contingent right to receive one (1) share of the Issuer's Common Stock upon settlement. The RSUs vested or vest as to 1/4 of the total award annually, with the first tranche vested on March 1, 2025, subject to continued service through each vesting date. The RSUs vested or vest as to 1/4 of the total award annually, with the first tranche vested on March 2, 2026, subject to continued service through each vesting date. The RSUs shall vest as to 1/4 of the total award annually, with the first tranche vesting on March 1, 2027, subject to continued service through each vesting date. 1/48 of the total option award shall vest monthly, subject to the reporting person's continued service through each vesting date, with the first tranche vesting on April 1, 2026.
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*
Gerber Hans-Peter
(Last) (First) (Middle)
C/O SUTRO BIOPHARMA, INC.
111 OYSTER POINT BLVD.
(Street)
SOUTH SAN FRANCISCO CA 94080
(City) (State) (Zip)
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)
CHIEF SCIENTIFIC OFFICER
3. Date of Earliest Transaction (Month/Day/Year)
03/01/2026
4. If Amendment, Date of Original Filed (Month/Day/Year)
 6. Individual or Joint/Group Filing (Check Applicable Line)
X Form filed by One Reporting Person
Form filed by More than One Reporting Person
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 03/01/2026 M 1,125 A $0 8,308 D
Common Stock 03/01/2026 F 463(1) D $20.47 7,845 D
Common Stock 03/02/2026 M 2,843 A $0 10,688 D
Common Stock 03/02/2026 F 1,170(1) D $20.55 9,518 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) (2) 03/01/2026 M 1,125 (3) 03/01/2028 Common Stock 1,125 $0 2,250 D
Restricted Stock Units (RSUs) (2) 03/02/2026 M 2,843 (4) 03/02/2029 Common Stock 2,843 $0 8,532 D
Restricted Stock Units (RSUs) (2) 03/02/2026 A 5,000 (5) 03/01/2030 Common Stock 5,000 $0 5,000 D
Stock Option (right to buy) $20.55 03/02/2026 A 40,000 (6) 03/02/2036 Common Stock 40,000 $0 40,000 D
Explanation of Responses:
1. Represents the number of shares of Common Stock that have been withheld by the Issuer to satisfy its income tax withholding and remittance obligations in connection with the net settlement of restricted stock units; does not represent a sale by the reporting person.
2. Each RSU represents a contingent right to receive one (1) share of the Issuer's Common Stock upon settlement.
3. The RSUs vested or vest as to 1/4 of the total award annually, with the first tranche vested on March 1, 2025, subject to continued service through each vesting date.
4. The RSUs vested or vest as to 1/4 of the total award annually, with the first tranche vested on March 2, 2026, subject to continued service through each vesting date.
5. The RSUs shall vest as to 1/4 of the total award annually, with the first tranche vesting on March 1, 2027, subject to continued service through each vesting date.
6. 1/48 of the total option award shall vest monthly, subject to the reporting person's continued service through each vesting date, with the first tranche vesting on April 1, 2026.
Remarks:
Effective as of 12:01 a.m. Eastern time on December 3, 2025, pursuant to a Certificate of Amendment to the Issuer's Restated Certificate of Incorporation previously approved by the Issuer's stockholders, and filed with the Delaware Secretary of State on December 2, 2025, the Issuer's Common Stock, par value $0.001 per share, underwent a 1-for-10 reverse stock split (the "Reverse Stock Split"). All amounts, including all dollar values, set forth herein have been adjusted to reflect the Reverse Stock Split.
/s/ David Pauling as attorney-in-fact 03/03/2026
** 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.

Source: View Original Filing on SEC EDGAR

FAQ

What insider transactions did STRO’s Chief Scientific Officer report?

Hans-Peter Gerber reported RSU vesting, related common share issuances, tax-withholding share dispositions, and new equity awards. Transactions included RSU conversions to common stock, issuer share withholding for taxes, a 5,000 RSU grant, and a 40,000-share stock option grant with time-based vesting.

Did the STRO insider sell shares in the open market?

The filing indicates no open-market sales by the insider. Shares labeled with code F were withheld by the issuer to satisfy income tax obligations on RSU settlements, with a footnote explicitly stating these do not represent sales by the reporting person.

What new RSU awards did STRO grant to its Chief Scientific Officer?

The Chief Scientific Officer received a grant of 5,000 restricted stock units. Footnotes state each RSU equals one common share upon settlement and that the award vests in four annual tranches, beginning March 1, 2027, subject to continued service through each vesting date.

What are the terms of the 40,000-share stock option reported for STRO?

The filing reports a stock option covering 40,000 shares of common stock. Footnotes explain that 1/48 of the total option vests monthly, provided continued service, with the first vesting tranche scheduled for April 1, 2026, creating a four-year, time-based vesting schedule.

How many STRO common shares did the insider receive from RSU vesting?

The insider acquired 1,125 and 2,843 shares of common stock through RSU conversions. These came from restricted stock units that vested on March 1 and March 2, 2026, respectively, with each RSU representing the right to receive one share upon settlement.

Why were some STRO shares disposed of in these transactions?

Dispositions coded F reflect issuer share withholding to cover income tax liabilities from RSU settlements. Specifically, 463 and 1,170 shares were withheld, at prices of $20.47 and $20.55, with footnotes clarifying these entries are tax-withholding events, not discretionary sales.