CytomX Therapeutics’ EpCAM-directed masked ADC varsetatug masetecan (Varseta-M; CX-2051) received FDA fast track designation for relapsed/refractory metastatic colorectal cancer. The designation follows phase 1 dose-expansion data from the ongoing CTMX-2051-101 trial. CytomX reported confirmed objective response rates of 6% (7.2 mg/kg), 20% (8.6 mg/kg) and 32% (10 mg/kg) in efficacy-evaluable patients, with median progression-free survival reported around 5–7 months across the expansion dosing cohorts. Disease control rates ranged from 84% to 90% across doses, with diarrhea identified as the most common treatment-related adverse event, including grade 3 diarrhea in 10% at the updated prophylactic regimen. The fast-track move sets up a potential registrational path, with CytomX indicating it plans a potential monotherapy registrational study in the first half of 2027 as it works toward expansion in this heavily pretreated population.