The FDA has placed a partial clinical hold on Blueprint Medicines’ phase 1/2 trial of BLU-222, an CDK2 inhibitor drug candidate for advanced solid tumors, because of visual adverse events — light sensitivity and blurred vision — observed in several patients.

The reported adverse events were mild except for one severe case and all events were “resolved with dose interruption or reduction,” the company said.

Patients currently enrolled in the study will continue taking the investigational drug, but no new  patients will be enrolled until the partial clinical hold is lifted.