CytomX Therapeutics received FDA fast track designation for varsetatug masetecan (Varseta-M; CX-2051), an EpCAM-directed masked antibody-drug conjugate, for relapsed/refractory metastatic colorectal cancer. The designation followed phase 1 dose-expansion data from CTMX-2051-101, with confirmed objective response rates climbing by dose and disease control rates near 90% across evaluable patients. CytomX also flagged a planned registrational monotherapy study window in 2027. The FDA program leans on the early efficacy signal despite limited patient numbers, while safety highlights included diarrhea with a reported grade 3 incidence tied to an updated prophylactic regimen.