CytomX’s Varsetatug Masetecan (EpCAM PROBODY® ADC) Continues to Demonstrate Positive Data Supporting Potential as a New Treatment Option in Late-Line Colorectal Cancer

Core Insights - CytomX Therapeutics announced positive Phase 1 expansion data for its EpCAM PROBODY ADC, varsetatug masetecan (Varseta-M), in late-line metastatic colorectal cancer (CRC) [2][3] Efficacy Data - Confirmed response rates in expansion cohorts were 32% at a 10 mg/kg Q3W dose and 20% at an 8.6 mg/kg Q3W dose [1] - Estimated median progression-free survival (PFS) was 7.1 months at 10 mg/kg and 6.8 months at 8.6 mg/kg [1][10] - Disease control rate (DCR) across the expansion doses of 7.2 mg/kg to 10 mg/kg was 88% [10] Patient Characteristics - A total of 93 patients with late-line metastatic CRC were enrolled in the study, with 60 patients in the Phase 1 expansion dose range [7] - Patients had a median of 3 prior lines of therapy, with 96% previously treated with irinotecan [7] Safety Profile - The most common treatment-related adverse event was diarrhea, with a Grade 3 diarrhea rate of 10% in the ongoing dose optimization cohorts [1][11] - Overall, treatment-related adverse events were primarily Grade 1 or Grade 2 in severity [9] Future Plans - The company plans to engage with the FDA mid-year to discuss potential registrational trial design for Varseta-M in late-line CRC [1][3] - A Phase 1 study evaluating the combination of Varseta-M with bevacizumab has been initiated, and a Phase 1b/2 chemotherapy combination study is expected to start by the end of 2026 [1][17]