Astellas walked away from its multi‑year collaboration with CytomX, exiting a partnership that originally carried up to $1.6–$1.7 billion in potential milestones. The split follows shifting development priorities at Astellas and regulatory reprioritizations and leaves CytomX to reassess programs previously covered by the alliance. Counterintuitively, CytomX reported clinically meaningful response signals from its masked, conditionally activated ADC varsetatug masetecan (Varseta‑M) in heavily pretreated colorectal cancer patients, with expansion‑cohort response rates in the 20–32% range at higher doses and progression‑free gains of several months. CytomX said diarrhea was the most common adverse event but generally manageable with prophylaxis. The combination of partnership termination and positive early efficacy data puts CytomX at a strategic crossroads: the company can advance Varseta‑M and seek a regulatory path or a new partner to fund larger studies while monetizing other platform assets. Investors and potential partners will weigh the ADC’s therapeutic window, safety management strategies, and the company’s broader balance sheet and pipeline as CytomX outlines next steps and engages regulators.