Sutro Biopharma (STRO) Status Update summary

Pipeline and platform advancements

• Plans to file three INDs over the next three years, starting with STRO-004, a high DAR exatecan ADC targeting tissue factor, and additional exatecan-based and dual payload ADCs.

• Cell-free protein synthesis platform enables modular, scalable, and precise engineering of complex ADCs, including dual payload and high DAR constructs, supporting rapid and site-specific ADC production for over 3,000 patients.

• Achieved a 4,000-liter GMP manufacturing run, reaching cost parity with traditional CHO-based production and demonstrating commercial-scale readiness.

• Platform allows for site-specific conjugation, optimized linker chemistry, and non-natural amino acid incorporation, enhancing safety and efficacy.

• Strong partnerships with Astellas and Ipsen support ongoing innovation and business development.

Scientific, clinical, and preclinical data highlights

• STRO-004 demonstrated potent anti-tumor activity in preclinical models, including low tissue factor-expressing tumors, with a widened therapeutic window and improved safety profile compared to benchmarks.

• High DAR (DAR-8) ADCs showed no significant increase in toxicity in non-human primate studies, supporting clinical advancement.

• Dual payload ADCs, including combinations of topo-1 inhibitors with microtubule inhibitors or PARP inhibitors, exhibited enhanced efficacy and the potential to overcome resistance.

• Immunostimulatory ADCs (iADCs) combining cytotoxic and immune-activating payloads showed superior and durable anti-tumor responses in preclinical models.

• Luvelta is advancing through two registrational trials in ovarian cancer and pediatric AML, with additional studies planned for NSCLC and endometrial cancer.

Product and platform highlights

• Luvelta is a precisely designed ADC with a hemiasterlin payload, showing activity in tumors with low to medium FRa expression.

• Demonstrated clinical activity in ovarian, endometrial, and pediatric AML, with manageable safety profiles.

• Next-generation ADCs and dual-payload technologies are being developed to overcome resistance and broaden patient benefit.

• STRO-004, a tissue factor-targeting ADC, is designed for enhanced stability and potency, with IND filing planned for 2H 2025.

• Bystander activity and optimized PK properties enable targeting of heterogeneous tumors and minimize off-target toxicity.