Aims: GARNET (NCT02715284) is assessing the antitumor activity and safety of dostarlimab monotherapy, an anti-programmed death (PD)-1 receptor humanized monoclonal antibody, in patients (pts) with solid tumors. We report efficacy based on investigator assessed (IA) for EC pts.
Methods: A phase 1, multicenter, open-label, single-arm, dose-escalation and cohort-expansion study. In 2 independent expansion cohorts of pts with recurrent/advanced EC (dMMR and MMRp , determined by immunohistochemistry [IHC]) that progressed on or after a platinum-based chemotherapy, pts received dostarlimab 500 mg IV Q3W for 4 cycles, then 1000 mg Q6W until disease progression, discontinuation, or withdrawal. Primary endpoints of objective response rate (ORR), disease control rate (DCR), and duration of response (DOR) by blinded independent central review using RECIST v1.1, and safety were reported previously (Oaknin ESMO 2020 LBA36). Immune-related (ir)ORR, irDCR, and irDOR by irRECIST based on IA, were prespecified secondary endpoints.
Results: 126 dMMR and 145 MMRp pts were enrolled and dosed 110 dMMR and 144 MMRp pts had measurable disease at baseline by IA and sufficient follow-up time (6 mo) and were included for efficacy analysis of irORR and irDOR; some additional pts were considered to have measurable disease at baseline by IA.
After median (range) follow-up of 16.5 (0.03-30.6) and 13.7 (0.03-33.1) months for dMMR and MMRp pts, irORR was 45.5% and 13.9%,irDCR was 63.6% and 42.4%, and irDOR was not reached and 12.2%, respectively.
Conclusions: Efficacy endpoints by RECIST v1.1 and irRECIST were similar. irDCR was particularly interesting in MMRp pts, a group with a poorer prognosis, but the potential benefit awaits confirmation in ongoing randomized controlled studies.
Funding: GSK 213346; editorial support from Fishawack Health, funded by GSK.
This abstract was previously presented at the Society of Gynecologic Oncology 2021 Annual Meeting and is submitted on behalf of the original authors with their permission.