CytomX reported positive dose‑expansion Phase I data for varsetatug masetecan (varseta‑M) in metastatic colorectal cancer, showing a 32% overall response rate and median progression‑free survival of 7.1 months at the 10 mg/kg dose. Varseta‑M is a Probody, conditionally activated ADC targeting EpCAM with a topoisomerase‑1 inhibitor payload sourced from ImmunoGen. The data rekindled investor interest despite Astellas recently terminating a long‑standing collaboration. The announcement produced dramatic intraday trading: shares spiked 75% then experienced sharp pullbacks across the following sessions, reflecting market sensitivity to early ADC readouts and doubts about durability and commercial positioning. Analysts at Jefferies framed varseta‑M as a potential multi‑billion dollar opportunity in colorectal and other EpCAM‑expressing tumors, but the stock’s volatility underscores how single early‑phase readouts can swing sentiment for small biotechs.