Sutro Biopharma, Inc.

Biotechnology • Healthcare • South San Francisco, CA, United States • STRO (NGM)

Quarter: Q4 2025 Reported: December 3, 2025 Sentiment: Negative

Sutro Biopharma, Inc. operates as a oncology company. The company develops site-specific and novel-format antibody drug conjugates (ADCs) that enables its proprietary integrated cell-free protein synthesis platform, XpressCF; and site-specific conjugation platform, XpressCF+. Its lead product candidate includes STRO-004, a tissue factor (TF) targeting ADC for the treatment of TF-expressing solid tumors, including cervical, lung, and breast cancer. The company also develops VAX-24 and Vax-31 pneumococcal conjugate vaccine candidates that is in Phase II/III clinical trials for the treatment of invasive pneumococcal disease; and STRO-003, an ADC directed against an anti-receptor tyrosine kinase-like orphan receptor 1 (ROR1) for the treatment of solid tumors, such as triple negative breast cancer, non-small cell lung cancer, and ovarian cancer, as well as hematological cancers. Sutro Biopharma, Inc. has collaboration and license agreements with Vaxcyte to discover and develop vaccine candidates for the treatment or prophylaxis of infectious diseases; Tasly Biopharmaceuticals Co., Ltd. to develop and commercialize STRO-002 in Greater China; Ipsen to develop and commercialize STRO-003, an ADC targeting ROR1; and Astellas Pharma Inc. to develop immunostimulatory ADC. The company was formerly known as Fundamental Applied Biology, Inc. Sutro Biopharma, Inc. was incorporated in 2003 and is headquartered in South San Francisco, California.

Analysis Summary

Sutro Biopharma, Inc. (STRO) executed a 1-for-10 reverse stock split, which became effective at 12:01 am Eastern time on December 3, 2025. This corporate action, approved by the Board on November 20, 2025, and previously authorized by stockholders within a 1-for-5 to 1-for-25 range, consolidates the company's common stock. Post-split, every ten shares of issued and outstanding common stock are automatically combined into one, reducing the total outstanding shares from approximately 85,193,912 to about 8,519,392. Fractional shares resulting from the split will be rounded up to the nearest whole share, benefiting stockholders who would otherwise receive less than one full share. The reverse stock split does not alter the par value of the common stock, the number of authorized shares, or any voting rights or other terms of the common stock. Furthermore, proportionate adjustments will be made to the exercise price and number of shares issuable under all outstanding stock options and equity incentive plans, as well as the employee stock purchase plan. The common stock will begin trading on a split-adjusted basis under a new CUSIP number (869367201) starting December 3, 2025. This filing is a corporate action report (Form 8-K) and, as such, does not provide details on financial performance, revenue, earnings, or forward guidance typically found in an earnings call transcript. The primary implication of such a split is generally to increase the per-share trading price, often to meet exchange listing requirements or enhance market perception, though the specific rationale beyond 'strategic adjustment' is not explicitly detailed in this document.

Key Highlights

• 1-for-10 reverse stock split effective December 3, 2025.
• Outstanding shares reduced from approximately 85.2 million to 8.5 million.
• Fractional shares will be rounded up to the nearest whole share.
• No change to ownership percentage (except for fractional rounding), par value, authorized shares, or voting rights.
• Proportionate adjustments made to stock options, equity incentive, and employee stock purchase plans.
• Common Stock will trade under a new CUSIP number (869367201) on a split-adjusted basis.

Financial Metrics

eps

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revenue

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guidance

net income

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Stock Performance (90 Days)

Data through Dec 24, 2025

Layoff Events

Earnings Calls

Positive Signals

• Board of Directors approved the specific ratio within the shareholder-approved range.
• Clear and defined effective date for the corporate action.
• Proactive management of the company's share structure.
• Fractional shares are rounded up, which is generally favorable to small shareholders.

Risks & Concerns

— The reverse stock split does not address underlying business performance or fundamental value.
— Potential for continued stock price decline post-split if market sentiment or operational performance does not improve.
— Risk of reduced trading liquidity due to fewer outstanding shares.
— May not achieve the desired long-term effect of attracting institutional investors or maintaining exchange listing requirements.