Sutro Biopharma has reported early clinical activity from the ongoing Phase 1 STRIVE-01 study of STRO-004, its Tissue Factor (TF)-targeting antibody-drug conjugate (ADC), in heavily pretreated patients with advanced solid tumors.
The update was announced on August 12, 2026, alongside the company’s second-quarter financial results.
STRO-004 is a TF-targeting DAR8 ADC with an exatecan payload that Sutro describes as a potential best-in-class candidate. The US-only Phase 1 STRIVE-01 trial began in November 2025 and is evaluating STRO-004 across multiple advanced solid tumors.
Dose levels from 1 to 5 mg/kg have enrolled 49 patients, with dose optimization currently ongoing between 4 and 5 mg/kg. The maximum tolerated dose has not yet been defined.
Patients enrolled in the study had received a median of 3 prior lines of therapy, ranging from 1 to 7, and represented 8 tumor types without selection based on TF expression. Among patients with pancreatic and colorectal cancer, 100% had received one or more prior irinotecan-containing regimens.
As of the July 24, 2026 data cutoff, Sutro reported multiple responses, including confirmed and ongoing unconfirmed partial responses, among RECIST-evaluable patients with pancreatic cancer, head and neck cancer, and non-small cell lung cancer at dose levels of 3–4 mg/kg.
Jane Chung, Chief Executive Officer of Sutro Biopharma, said:
“We have observed early clinical responses alongside favorable safety, tolerability, and a differentiated pharmacokinetic (PK) profile in patients with few remaining treatment options.”
Chung said the findings strengthened the company’s confidence in STRO-004’s potential to provide meaningful clinical benefit, support future combination strategies, and further validate Sutro’s proprietary ADC platform.
Safety and Pharmacokinetics
Sutro described the emerging tolerability profile of STRO-004 as favorable, with adverse events reported as mostly low grade.
The overall discontinuation rate due to adverse events was 6%. All-grade treatment-related adverse events occurring in more than 15% of patients included:
- Nausea: 33%
- Fatigue: 29%
- Anemia: 18%
Other treatment-related adverse events occurring in more than 5% of patients included decreased neutrophil count (6%) and decreased platelet count (6%).
TF-related events included epistaxis (12%), stomatitis (10%), mucosal inflammation (8%), conjunctivitis (8%), and dry eye (7%), with these events predominantly Grade 1–2. Grade 3 or higher anemia occurred in 14% of patients, with all cases reported as Grade 3.
Dose-limiting toxicities were observed only at the highest dose tested, 5 mg/kg, and appeared to be largely driven by target-related toxicity. They resulted in dose reductions but no study-drug discontinuations.
Sutro also reported dose-proportional ADC exposure across all doses, with no evidence of target-mediated drug disposition. STRO-004 had a half-life of nearly 7 days while preserving 98% of its DAR8 configuration, with free exatecan concentrations remaining low, delayed, and formation-limited.
Hans-Peter Gerber, PhD, Chief Scientific Officer of Sutro Biopharma, said:
“Compared with conventional DAR8 exatecan ADCs, STRO-004 delivered 25-50% more ADC exposure with at least 50% less circulating payload concentration, allowing us to dose at the highest end of the dosing range for the class.”
Sutro expects to provide the next update from STRIVE-01 in the first half of 2027, with initiation of expansion cohorts also planned for the first half of 2027.
Additional ADC Pipeline Updates
Sutro also provided updates on other programs in its ADC pipeline.
STRO-006, a highly selective integrin β6 (ITGB6)-targeting DAR8 exatecan ADC designed for the treatment of multiple solid tumors, remains on track to enter a Phase 1 clinical trial in the third quarter of 2026.
The company is also advancing STRO-227, its wholly owned PTK7-targeting DAR10 dual-payload ADC containing MMAE at DAR2 and exatecan at DAR8. The program remains on track for IND submission in 2026.
Under Sutro’s collaboration with Astellas, two dual-payload immunostimulatory ADC programs are progressing. The first, targeting TROP2, continues to actively dose patients and resulted in a $10 million milestone payment received by Sutro in April 2026.
The second program is also advancing under the collaboration, with Sutro expecting Astellas to bring it into the clinic by the end of 2026.
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