Form 4: Sutro Biopharma CSO Settles RSUs, Increases Stock Holdings

Sutro Biopharma's Chief Scientific Officer, Hans-Peter Gerber, acquired 37,500 shares of common stock through RSU settlement and disposed of 13,417 shares for tax withholding.

Summary

• Hans-Peter Gerber, Chief Scientific Officer of Sutro Biopharma, Inc. (STRO), reported transactions on September 18, 2025.
• Gerber acquired 37,500 shares of common stock upon the settlement of Restricted Stock Units (RSUs) at a price of $0 per share.
• Concurrently, 13,417 shares of common stock were disposed of by the issuer to satisfy income tax withholding obligations related to the RSU settlement, at a price of $0.9 per share.
• Following these transactions, Gerber's direct beneficial ownership of common stock increased by a net of 24,083 shares (37,500 acquired 13,417 disposed).
• Gerber now directly beneficially owns 54,832 shares of Sutro Biopharma common stock.
• After the settlement of 37,500 RSUs, Gerber continues to beneficially own 75,000 unvested Restricted Stock Units.
• Each RSU represents a contingent right to receive one share of the Issuer's Common Stock upon settlement.
• The RSU award vests annually as to 1/4th of the total award, with vesting commencing on September 18, 2024, subject to continued service.

Sentiment

Score: 6

Explanation: The sentiment is slightly positive as it reflects a routine vesting of equity compensation, indicating continued executive service and a net increase in direct stock ownership, which aligns management interests with shareholders. The tax-related disposition is a neutral, standard event.

Positives

• The acquisition of 37,500 shares of common stock through RSU settlement indicates the vesting of equity compensation, reflecting continued service and alignment of management interests with shareholders.
• The net increase of 24,083 shares in direct common stock ownership demonstrates a growing stake in the company by a key executive.

Negatives

• The disposition of 13,417 shares, while for tax withholding purposes and not a direct sale by the reporting person, reduces the immediate increase in direct beneficial ownership from the RSU settlement.

Future Outlook

The remaining 75,000 unvested Restricted Stock Units, which vest annually as to 1/4th of the total award, indicate future equity compensation events contingent on the Chief Scientific Officer's continued service to the Issuer.

Industry Context

This is a routine insider transaction common in the biotechnology industry, where equity compensation, such as Restricted Stock Units, is a standard component of executive remuneration. The vesting and settlement of RSUs, followed by tax withholding, is a typical event for executives in publicly traded companies.

Stakeholder Impact

• Shareholders: The increase in direct beneficial ownership by a key executive may be viewed positively as it aligns management's interests with shareholder value creation.
• Employees: The RSU vesting demonstrates the company's compensation structure for executives, which can influence employee perception of equity incentives.

Next Steps

• Future annual vesting of the remaining 75,000 Restricted Stock Units, subject to Hans-Peter Gerber's continued service to Sutro Biopharma.

Key Dates

Keywords

Sutro Biopharma, STRO, Form 4, Insider Transaction, Restricted Stock Units, RSU, Equity Compensation, Beneficial Ownership, Chief Scientific Officer