Single-Payload ADCs
STRO-004 | Tissue Factor
STRO-004 is a next-generation antibody-drug conjugate (ADC) targeting Tissue Factor (TF), a clinically validated target broadly expressed across multiple solid tumors with significant unmet need. Developed using Sutro Biopharma’s proprietary cell-free platform, STRO-004 features an Fc-silent, high affinity antibody, with site-specific β-glucuronidase cleavable linker and exatecan payload at a homogenous drug-to-antibody ratio of 8 (DAR8). This design aims to enhance stability, reduce off-target toxicity, and maximize efficacy.
In preclinical models, STRO-004 has demonstrated robust anti-tumor activity across a broad range of TF-expressing cancers, supporting its potential as a best-in-class therapy. The program is currently advancing in a Phase 1 trial evaluating activity across multiple solid tumor types.
STRO-006 | Integrin β6
STRO-006 is an optimally designed ADC targeting integrin β6 (ITGB6), a tumor-associated antigen expressed across several high-prevalence solid tumors, non-small cell lung cancer, or NSCLC, and head and neck cancer. This candidate delivers a potent exatecan payload (DAR 8) with a high-affinity antibody that binds to ITGB6 without disrupting TGFb signaling. Sharing the same core design elements as STRO-004, STRO-006 is designed for low platform toxicity and optimized ADC exposure. This profile is intended to deliver a wider therapeutic index than other ADCs by enhancing selectivity, stability, and pharmacokinetics.
Preclinical data demonstrate strong anti-tumor activity and durability. STRO-006 is advancing toward IND submission, with the goal of addressing a broad range of ITGB6-expressing tumors.
Dual-Payload ADCs
STRO-227 | PTK7
STRO-227 is Sutro’s first wholly–owned dual-payload ADC targeting PTK7, a clinically validated, pan-tumor antigen associated with poor prognosis and enriched on cancer stem cells. Leveraging Sutro’s proprietary cell-free platform, STRO-227 delivers two complementary cytotoxic payloads within a single molecule (DAR 10; 8 exatecan + 2 MMAE), enabling simultaneous targeting of multiple tumor survival pathways. Built on the same design principles as STRO-004 and STRO-006, STRO-227 is engineered to minimize free circulating payload levels while maximizing ADC exposure, establishing a wide therapeutic index and a differentiated safety profile.
In preclinical models, STRO-227 has improved the anti-tumor activity compared to single-payload ADCs, with the potential to overcome resistance in tumors progressing after prior single-payload ADC treatment. Preclinical data have also shown broad anti-tumor activity across multiple tumor types and support a favorable tolerability profile, even with the added complexity of a dual-payload design.
STRO-227 represents next-generation ADC engineering, designed to deepen and extend anti-tumor responses beyond the capability of single payload approaches. The program is progressing toward IND submission.
STRO-00Y | Emerging Dual-Payload ADC
STRO-00Y is a next-generation ADC in preclinical development, engineered to address tumor heterogeneity and drug resistance. By combining payloads at precise ratios with Sutro’s proprietary cell-free platform, STRO-00Y is designed to deliver higher anti-tumor activity while reducing exposure to free payloads in the body. This program advances Sutro’s goal of redefining what’s possible in ADC therapy, targeting solid tumors across a wide range of difficult-to-treat indications.