CytomX Therapeutics disclosed expansion‑cohort Phase 1 data for its masked antibody‑drug conjugate Varseta‑M showing objective response rates of roughly 20–32% in heavily pretreated metastatic colorectal cancer and progression‑free survival gains of 6.8–7.1 months in top dose groups. The company said adverse events were manageable but noted persistent severe diarrhea in a subset of patients despite prophylaxis, and plans to engage the FDA on a monotherapy development path. Separately, Astellas terminated a six‑year collaboration on T‑cell engaging bispecifics with CytomX, withdrawing from a previously announced $1.6 billion partnership. The exit underlines shifting strategic priorities among big pharma partners even as small biotechs report encouraging clinical signals. CytomX will now press forward on Varseta‑M development while navigating the commercial and alliance fallout from its partner’s departure.