Objectives Dostarlimab is a humanized programmed death 1 (PD-1) receptor monoclonal antibody that blocks interactions with PD-1 ligands. GARNET is a phase 1 study assessing antitumor activity and safety of dostarlimab monotherapy in patients with advanced solid tumors.
Methods This multicenter, open-label, single-arm study is conducted in 2 parts: dose escalation and expansion. Patients with advanced or recurrent mismatch repair–deficient (dMMR) or microsatellite instability–high (MSI-H) endometrial cancer (EC) or mismatch repair–proficient (MMRp) EC that progressed on or after a platinum regimen received dostarlimab 500 mg intravenously Q3W for 4 cycles, then 1000 mg Q6W until disease progression or discontinuation. Primary endpoints were objective response rate (ORR) and duration of response by BICR using RECIST v1.1. Here we report ORR in dMMR/MSI-H and MMRp EC by prior lines of therapy (LOTs).
Results Efficacy analyses included 108 dMMR/MSI-H and 142 MMRp patients. ORR was 43.5% in dMMR/MSI-H and 13.4% in MMRp. ORR was slightly higher (47.8%) in patients with dMMR/MSI-H with 1 prior LOT but lower (35.9%) in those who received ≥2 prior LOTs. In the MMRp population, ORR was similar, regardless of prior LOTs. Safety has been previously reported.1
Conclusions Dostarlimab demonstrated antitumor activity in recurrent or advanced dMMR/MSI-H and MMRp EC regardless of number of prior LOTs. Patients with dMMR/MSI-H EC who received 1 prior LOT had slightly higher ORR than those who received ≥2 prior LOTs. 1. Oaknin A, et al. Ann Oncol 2020;31(suppl 4):S1142–S1215.
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