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, Inc. is conducting a primary offering of 7,868,383 shares of common stock at $13.98 per share, raising gross proceeds of $109,999,994. After $6,600,000 in underwriting discounts and commissions, Sutro expects approximately $103,399,995 in proceeds before expenses and estimates net proceeds of about $102.7 million.
The company plans to use the cash, together with existing balances, for general corporate purposes, including research, clinical and process development, manufacturing, working capital, potential acquisitions or investments, and capital expenditures. Combined with cash, cash equivalents and marketable securities as of January 1, 2026 and the additional $110.0 million before costs, Sutro expects to have approximately $251.4 million in capital resources, which it estimates will fund operations into the second quarter of 2028.
As context, 8,563,888 shares of common stock were outstanding as of September 30, 2025. The offering price of $13.98 per share is expected to result in immediate dilution of $13.04 per share to new investors, based on an as adjusted net tangible book value of $0.94 per share after the transaction. Leerink Partners LLC, TD Securities (USA) LLC and LifeSci Capital LLC are underwriting the deal, and the company, its directors and executive officers are subject to 60‑day and 90‑day lock-up periods, respectively, with specified exceptions.
Affinity Asset Advisors, LLC and its managing member Michael Cho report beneficial ownership of 748,382 shares of Sutro Biopharma, Inc. common stock, equal to approximately 8.8% of the company’s outstanding shares based on 8,519,392 shares outstanding as of December 3, 2025.
The shares are held by Affinity Healthcare Fund, LP, for which Affinity Asset Advisors serves as investment manager. As of the current reporting date, the reporting persons have sole voting and dispositive power over these shares and certify that the position is held in the ordinary course of business, without the purpose or effect of changing or influencing control of Sutro Biopharma.
A shareholder of STRO has filed a notice of proposed sale under Rule 144 for up to 8,929 shares of common stock through Morgan Stanley Smith Barney LLC on or around 01/20/2026, to be sold on the NASDAQ. The filing lists an aggregate market value of $130,961.76 for these shares and notes that 8,513,529 shares of this class were outstanding. The securities to be sold were acquired via a mix of stock option exercise and restricted stock awards from the issuer in 2025–2026, some paid in cash and some noted as not applicable for cash payment. By signing, the seller represents they are not aware of undisclosed material adverse information about the issuer’s operations.
Sutro Biopharma, Inc. reported that it has regained compliance with Nasdaq’s minimum bid price requirement for continued listing on The Nasdaq Global Market. Nasdaq’s Listing Qualifications staff confirmed that, as of December 16, 2025, the closing bid price of Sutro’s common stock had been at least $1.00 per share for 10 consecutive business days and that the company satisfies all other applicable listing criteria. This means the prior listing deficiency has been resolved and the related matter is now closed.
The company had previously been notified on June 20, 2025 that its stock had traded below $1.00 per share for 30 consecutive business days, putting it out of compliance with Nasdaq Listing Rule 5450(a)(1). The new notice confirms that Sutro has successfully corrected this issue and remains listed on The Nasdaq Global Market.
Sutro Biopharma CEO and director Jane Chung reported the vesting and settlement of restricted stock units on 12/12/2025. She received 2,500 shares of common stock at an exercise price of $0, and 894 shares were withheld by the company at $8.015 per share to cover tax obligations, which the filing states does not represent a sale by her. Following these transactions, she directly owns 13,891 shares of common stock and 5,000 RSUs, each RSU representing the right to receive one share upon settlement. The award vests in annual quarters, with the first tranche having vested on December 1, 2024. All share and dollar amounts reflect a 1-for-10 reverse stock split of Sutro Biopharma common stock that became effective on December 3, 2025.
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) 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 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) 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.