CytomX Therapeutics (CTMX) said Monday a Phase 1 clinical trial evaluating varsetatug masetecan in patients with advanced colorectal cancer yielded confirmed response rates of up to 32%.

Patients receiving the 10-milligram per kilogram dose demonstrated an estimated median progression-free survival of 7.1 months, the company said.

The 8.6-milligram per kilogram cohort showed a 20% response rate alongside a 6.8-month estimated progression-free survival period, CytomX said.

The company also said severe diarrhea occurred in 10% of trial participants who received optimized preventative medications during the evaluation.

Shares of the company were up over 52% in Monday premarket activity.