The FDA granted fast track designation to CytomX Therapeutics’ EpCAM-directed, masked, conditionally activated antibody-drug conjugate varsetatug masetecan (Varseta-M) for relapsed/refractory metastatic colorectal cancer. The move follows phase 1 dose-expansion data from the CTMX-2051-101 trial. In the prioritized expansion cohorts, confirmed objective response rates ranged from 6% at the lowest studied dose to 32% at 10 mg/kg, with disease control rates in the mid-to-high range across dose levels. CytomX also noted diarrhea as the most common treatment-related adverse event, including grade 3 events under an updated prophylactic regimen. CytomX said it plans a registrational monotherapy study in the first half of 2027, using fast track status to support development momentum in a population with continued unmet need.