Will GSK/Tesaro’s Checkpoint Inhibitor Be Able to Compete With Merck’s Keytruda?

Only a few months after GlaxoSmithKline acquired Waltham, Mass.-based Tesaro, Tesaro released promising data from its Phase I/II GARNET study of dostarlimab in endometrial cancer. An anti-PD-1 antibody checkpoint inhibitor, many are looking to dostarlimab as being a potential competitor with Merck’s blockbuster Keytruda. Tesaro and GSK presented data from the trial at the 2019 Society for Gynecologic Oncology (SGO) Annual Meeting on Women’s Cancer in Honolulu, Hawaii. The ongoing Phase I/II GARNET trial evaluated dostarlimab alone in patients with advanced solid tumors. It has a number of components, including a weight-based dose escalation study and a fixed-dose safety study, both of which are completed. Part 2B of the trial includes four expansion cohorts, MSI-H endometrial cancer, MSI-H non-endometrial cancer, MSS endometrial cancer, and non-small cell lung cancer. The data presented was in women with recurrent or advanced endometrial cancer who progressed on or after a platinum-based treatment. The preliminary data show a clinically meaningful and durable response rate in these patient populations regardless of microsatellite instability status. It also showed that dostarlimab was well tolerated with a safety profile consistent with anti-PD-1 therapies.