Checkpoint Therapeutics, Inc. announced that the ongoing multi-center clinical trial of CK-301 has been expanded to enroll patients in three cohorts intended to support requests for accelerated approval and Biologics License Application (BLA) submissions to the U.S. Food and Drug Administration (FDA). These cohorts include: Microsatellite instability-high (MSI-H) endometrial cancer that has progressed following one or two prior anti-cancer therapies, Microsatellite stable (MSS) endometrial cancer that has progressed following one or two prior anti-cancer therapies and MSI-H or mismatch repair deficient (dMMR) colorectal cancer that has progressed on or after, or been intolerant of, previous treatments, including a fluoropyrimidine- and oxaliplatin- and irinotecan-based chemotherapy. Each cohort is evaluating a fixed dose of 800 mg CK-301 every two weeks (Q2W). The primary endpoint for each cohort is objective response rate (ORR), and secondary endpoints include duration of response (DOR), progression-free survival (PFS), and overall survival (OS). The ongoing trial is also enrolling cohorts of patients with non-small cell lung cancer (NSCLC) and cutaneous squamous cell carcinoma. The Phase 1, open-label, multi-center trial is evaluating the safety and tolerability of ascending doses of CK-301 in checkpoint therapy-naïve patients with selected recurrent or metastatic cancers. Following completion of dose escalation in 2018, multiple dose expansion cohorts were initiated. Preliminary data from the ongoing trial suggest that CK-301 is safe and well-tolerated across dose levels ranging from 200 mg to 800 mg administered every two weeks and 1200 mg administered every three weeks, with treatment-related adverse events consistent with marketed anti-PD-1/PD-L1 antibodies.