Welcome to our dedicated page for Sutro Biopharma SEC filings (Ticker: STRO), a comprehensive resource for investors and traders seeking official regulatory documents including 10-K annual reports, 10-Q quarterly earnings, 8-K material events, and insider trading forms.
Sutro Biopharma filings document the regulatory record of a clinical-stage oncology biotechnology company developing site-specific antibody-drug conjugates. Its SEC disclosures cover operating and financial results, research and development priorities, clinical and regulatory updates for ADC programs, collaboration-related matters, risk factors, and capital-structure activity involving its common stock.
The company’s filings also include definitive proxy materials on shareholder voting, board matters, executive compensation and equity awards. Form 8-K reports document material events such as agreement terminations, restructuring costs, Nasdaq listing-rule notices and compliance updates, and other corporate actions affecting governance, reporting status and financing flexibility.
Sutro Biopharma (STRO) filed its Q3 2025 report, showing revenue of $9.7 million, up from $8.5 million a year ago. For the nine months, revenue reached $90.8 million versus $47.2 million, driven by collaboration activity including accelerated recognition tied to changes in partner programs. Q3 net loss was $56.9 million compared to $48.8 million, reflecting restructuring charges of $9.6 million in the quarter and $49.0 million year-to-date.
Unrestricted cash, cash equivalents and marketable securities totaled $167.6 million as of September 30, 2025, and management expects this to fund operations for at least 12 months after filing. Total assets were $209.7 million; the company reported a stockholders’ deficit of $87.3 million, largely due to an accumulated deficit of $931.2 million and a deferred royalty obligation of $209.9 million. Deferred revenue declined to $12.7 million from $82.3 million as obligations were satisfied. Sutro is prioritizing three preclinical ADC programs, exiting its internal GMP facility by year-end, and has announced workforce reductions that cumulatively approximate two-thirds. The company received a Nasdaq minimum bid price notice with a compliance period through December 17, 2025.
Sutro Biopharma (STRO) furnished an 8-K announcing it issued a press release with financial results for the quarter ended September 30, 2025. The press release is provided as Exhibit 99.1. The company states the information under Item 2.02, including Exhibit 99.1, is being furnished and not filed under the Exchange Act, and is not subject to Section 18 liabilities nor incorporated by reference except as expressly stated.
Sutro Biopharma (STRO) disclosed an insider stock purchase by its Chief Executive Officer and Director, Jane Chung. On 10/15/2025, the reporting person purchased 12,500 shares of common stock at $0.8009 per share (transaction code P). Following this transaction, the reporting person beneficially owned 122,850 shares, held in direct ownership.
No derivative securities were reported in this filing.
Sutro Biopharma (STRO) reported an insider purchase on Form 4. CFO Gregory K. Chow bought 19,750 shares of common stock on 10/15/2025 with transaction code P (purchase). The weighted average price was $0.81, with individual trades executed between $0.8099 and $0.8100. Following the transaction, he beneficially owned 19,750 shares, held directly.
Sutro Biopharma (STRO) reported an insider purchase by its Chief Scientific Officer, Hans-Peter Gerber. On October 15, 2025, he bought 17,000 shares of common stock at a weighted average price of $0.8004 per share in open-market transactions. Following the trade, he beneficially owned 71,832 shares, held directly.
The filing notes the shares were acquired through multiple executions within a price range of $0.7932 to $0.8015, and provides to interested parties the breakdown of shares purchased at each price upon request.
Sutro Biopharma (STRO) reported an insider share purchase. A director bought 50,000 shares of common stock on 10/15/2025 at a price of $0.799 per share, according to a Form 4 filing. Following the transaction, the reporting person beneficially owns 50,000 shares, held directly.
Sutro Biopharma (STRO): Insider transaction reported. A company officer (Chief Administrative Officer & General Counsel) purchased 12,504 shares of Common Stock on 10/15/2025 at $0.7992 per share, according to a Form 4 filing.
Following the transaction, the officer directly beneficially owns 71,737 shares. The total includes 2,500 shares acquired through the company’s Employee Stock Purchase Plan, as noted in the filing’s explanation.
Sutro Biopharma, Inc. reported a new organizational restructuring to focus on three preclinical antibody-drug conjugate (ADC) programs and its research and development collaborations. The company expects this restructuring, together with anticipated near-term milestone payments, to extend its cash runway into at least mid-2027. As part of the plan, Sutro intends to reduce its workforce by approximately one-third. The company estimates total cash payments and costs related to the program prioritization and workforce reduction will be approximately $4.1 million to $4.3 million, with a significant majority expected to be paid in the fourth quarter of 2025. Following prioritization of its ADC programs, Sutro expects initial clinical data from STRO-004, its next-generation Tissue Factor-targeting exatecan ADC, to be available in 2026.
Hans-Peter Gerber, Chief Scientific Officer of Sutro Biopharma, acquired equity and vested awards on 09/18/2025. The Form 4 shows 37,500 restricted stock units (RSUs) were recorded as acquired and will settle into common stock; each RSU converts to one share on settlement. Following the transactions, Mr. Gerber beneficially owned 75,000 shares of common stock. Additionally, the issuer withheld 13,417 shares
Hans-Peter Gerber, Chief Scientific Officer of Sutro Biopharma, acquired equity and vested awards on 09/18/2025. The Form 4 shows 37,500 restricted stock units (RSUs) were recorded as acquired and will settle into common stock; each RSU converts to one share on settlement. Following the transactions, Mr. Gerber beneficially owned 75,000 shares of common stock. Additionally, the issuer withheld 13,417 shares
David Pauling, Chief Administrative Officer and General Counsel of Sutro BioPharma, Inc. (STRO), amended his Form 3 to correct the number of shares he beneficially owns. The filing reports 56,733 shares of common stock held directly. The amendment notes the original Form 3 filed on April 8, 2025 misstated the total and is otherwise unchanged. The event date requiring the statement is 04/04/2025, and the amended Form 3/A is signed by Mr. Pauling on 09/12/2025.