Blocking PD-1 in Tumors with Faulty DNA Repair.

A phase II study shows that DNA mismatch repair deficiency can render tumors highly sensitive to the PD-1 inhibitor pembrolizumab. Patients with a range of solid tumors, including colorectal and endometrial cancers, with the deficiency responded well and durably to immune checkpoint blockade, with minimal toxicity. ©2016 American Association for Cancer Research.