Sutro Biopharma Presents Promising Preclinical Data Across its Pipeline of Next-Generation Single and Dual-Payload ADC Programs at AACR 2026

STRO-004 demonstrates robust and consistent antitumor activity across multiple TF-expressing solid tumor PDX models, with improved efficacy versus benchmark ADCs

STRO-006 and STRO-227 show meaningful, dose-dependent antitumor activity across solid tumor models

Presentation of TROP2-targeted immunostimulatory ADC program partnered with Astellas highlights the potential of Sutro's platform for developing dual-payload ADCs

SOUTH SAN FRANCISCO, Calif., April 19, 2026 (GLOBE NEWSWIRE) -- Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ:STRO), a clinical-stage oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), today announced promising preclinical data across its pipeline of next- generation ADCs in five posters and one oral presentation at the American Association for Cancer Research (AACR) Annual Meeting 2026. Of note, results from a preclinical study of STRO-004, its DAR8 Topo1 ADC targeting Tissue Factor (TF), were reviewed today in an oral presentation titled "STRO-004, an exatecan-based next-generation tissue factor (TF)-targeted ADC, demonstrates superior efficacy across TF-expressing solid tumors in a comprehensive single-mouse PDX trial."

In the preclinical study, STRO-004 demonstrated robust and consistent antitumor activity across a broad range of TF-expressing solid tumor patient-derived xenograft (PDX) models, with improved efficacy compared to benchmark ADCs. At a single, clinically relevant dose of 5 mg/kg, STRO-004 achieved remarkable disease control and tumor reduction across multiple tumor types. STRO-004's favorable tolerability, with a highest non-severely toxic dose (HNSTD) of 50 mg/kg, and pharmacokinetic profile are expected to enable increased drug exposure and payload delivery, supporting the Company's belief that STRO-004 will demonstrate superior depth and durability of response in the clinic. Exploratory biomarker analyses provide preliminary insight into STRO-004's mechanism of action, suggesting potential for combination studies addressing specific indications in either early or late lines of treatment.

"The STRO-004 preclinical data presented today underscore the potential of our next-generation ADCs to drive meaningful activity across multiple solid tumors," said Jane Chung, Sutro's Chief Executive Officer. "As STRO-004 advances in the clinic – with initial results from our Phase 1 study expected in mid-2026 – these preclinical data further strengthen our confidence in its potential across indications. More broadly, they underscore the versatility of our platform to generate differentiated ADCs across many targets and payloads, supporting a pipeline designed to address significant unmet need in cancer."

In addition to the oral presentation, Sutro will present multiple posters highlighting advances across its ADC pipeline and discovery platforms, the full details of which are included below.

Select Poster Highlights:

• Preclinical data for STRO-006, an integrin β6-targeting ADC (DAR 8 exatecan), demonstrated robust, dose-dependent antitumor activity across multiple solid tumor models at a single, clinically relevant dose of 5 mg/kg, including non-small cell lung cancer (NSCLC) and head and neck cancers. The program also shows a favorable pharmacokinetic and tolerability profile, supporting its potential as a differentiated next-generation ADC with IND submission planned for 2026.
• Preclinical data for STRO-227, a PTK7-targeting dual-payload ADC (DAR 10; 8 exatecan + 2 MMAE), demonstrated robust, dose-dependent antitumor activity across multiple solid tumor models, including breast, ovarian and NSCLC, with improved efficacy versus single-payload ADCs. The program also shows favorable pharmacokinetics, stable payload delivery, and tolerability comparable to benchmark ADCs, supporting the potential of its dual-payload design. These findings position STRO-227 as a differentiated ADC with broad applicability across solid tumors. Sutro expects to file an IND for STRO-227, its first wholly-owned dual-payload ADC, in late 2026.
  
  
  
  

Full Poster Presentation Details:

• Poster: "Phase 1 open-label study to evaluate safety, pharmacokinetics, and preliminary anti-tumor activity of STRO-004 in adults with refractory/recurrent metastatic solid tumors"
  • Session Date and Time: Monday, April 20, 2026; 9:00 AM-12:00 PM PT
• Poster: "STRO-006: An Integrin beta-6–targeting ADC demonstrates favorable safety profile and potent antitumor activity in preclinical solid tumors"
  • Session Date and Time: Monday, April 20, 2026; 9:00 AM-12:00 PM PT
• Poster: "Preclinical characterization of STRO-227: A PTK7-targeting dual-payload ADC with topoisomerase 1 and tubulin inhibitors"
  • Session Date and Time: Monday, April 20, 2026; 9:00 AM-12:00 PM PT
• Poster: "The HER2-targeting dual-payload antibody-drug conjugate combining a topoisomerase I inhibitor and a microtubule inhibitor demonstrates superior efficacy and overcomes resistance to single-payload ADCs in xenograft models"
  • Session Date and Time: Monday, April 20, 2026; 9:00 AM-12:00 PM PT
• Poster: "Sutro's Site-Specific Dual-Payload ADCs Combining TOPO1i and DNA Damage Response Inhibitors to Enhance Efficacy, Overcome Resistance, and Improve Safety"
  • Session Date and Time: Tuesday, April 21, 2026; 9:00 AM-12:00 PM PT
    
    
    
    

In addition to these presentations, Sutro's strategic partner, Astellas Pharma, also reviewed preclinical results from its TROP2-targeted iADC program at AACR today. The oral presentation, titled "ASP2998, a TROP2-targeted immunostimulatory antibody-drug conjugate (iADC) with dual payloads, demonstrates potent efficacy and a favorable safety profile in nonclinical models," highlighted the company's progress in the development of next-generation iADCs leveraging Sutro's cell-free protein synthesis platform. ASP2998 is a first-in-class iADC that combines cytotoxic and immune-stimulatory mechanisms to enhance antitumor efficacy. Inclusion of a STING agonist augments the antitumor efficacy, immune activation and durable tumor immunity of ASP2998, supporting its superior activity over toxin-only anti-TROP2 ADCs. Preclinically, ASP2998 demonstrated a favorable safety profile, supporting a promising therapeutic index. ASP2998 entered the clinic earlier this year and is actively dosing patients.

Following the congress, the Company's presentations will be made available in the Scientific Publications section of Sutro Biopharma's website at www.sutrobio.com.

About Sutro Biopharma

Sutro Biopharma, Inc. is a clinical-stage biotechnology company advancing a next-generation antibody-drug conjugate (ADC) platform designed to deliver single- and dual-payload ADCs that enable meaningful breakthroughs for patients with cancer. By fully optimizing the antibody, linker, and payload, Sutro's cell-free platform produces ADCs that are engineered to improve drug exposure, reduce side effects, and expand the range of treatable tumor types. With unique capabilities in dual-payload ADCs, Sutro aims to overcome treatment resistance and redefine what's possible in cancer therapy. The Company's pipeline of single- and dual-payload ADCs targets large oncology markets with limited treatment options and significant need for improved therapies.

For more information, follow Sutro on social media @Sutrobio or visit www.sutrobio.com.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, statements regarding the therapeutic potential and anticipated clinical benefits of STRO-004, STRO-006, STRO-227, and other ADC product candidates; Astellas' development of ASP2998; anticipated preclinical and clinical development activities; timing of announcements of IND submissions, trial initiation, clinical results, and other regulatory filings; outcome of discussions with regulatory authorities; potential benefits of the Company's product candidates and platform; potential business development and partnering transactions; and potential market opportunities for the Company's product candidates; the timing and receipt of anticipated future milestone payments. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Although the Company believes that the expectations reflected in such forward-looking statements are reasonable, the Company cannot guarantee future events, results, actions, levels of activity, performance or achievements, and the timing and results of biotechnology development and potential regulatory approval is inherently uncertain. Forward-looking statements are subject to risks and uncertainties that may cause the Company's actual activities or results to differ significantly from those expressed in any forward-looking statement, including risks and uncertainties related to the Company's ability to advance its product candidates, the receipt and timing of potential regulatory designations, approvals and commercialization of product candidates, the market size for the Company's product candidates being smaller than anticipated, clinical trial sites, supply chain and manufacturing facilities, the Company's ability to obtain, maintain and recognize the benefits of certain designations received by product candidates, the timing and results of preclinical and clinical trials, the Company's ability to fund development activities and achieve development goals, the Company's ability to protect intellectual property, and the Company's commercial collaborations with third parties and other risks and uncertainties described under the heading "Risk Factors" in documents the Company files from time to time with the Securities and Exchange Commission. These forward-looking statements speak only as of the date of this press release, and the Company undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date hereof.

Investor Contact

Emily White

Sutro Biopharma

(650) 823-7681

[email protected]

Media Contact

Amy Bonanno

Lyra Strategic Advisory

[email protected]