Safety of dostarlimab in combination with chemotherapy in patients with primary advanced or recurrent endometrial cancer in a phase III, randomized, placebo-controlled trial (ENGOT-EN6-NSGO/GOG-3031/RUBY)

In Part 1 of the phase III RUBY trial (NCT03981796) in patients with primary advanced or recurrent endometrial cancer (EC), dostarlimab plus carboplatin-paclitaxel (CP) significantly improved progression-free survival and overall survival compared with CP alone. Limited safety data have been reported for the combination of immunotherapies plus chemotherapy in this setting. The objective of this analysis was to identify the occurrence of treatment-related adverse events (TRAEs) and immune-related adverse events (irAEs) and to describe irAE management in Part 1 of the RUBY trial. RUBY is a phase III, randomized, double-blind, multicenter study of dostarlimab plus CP compared with CP alone in patients with primary advanced or recurrent EC. Patients were randomized 1:1 to dostarlimab 500 mg, or placebo, plus CP every 3 weeks for 6 cycles, followed by dostarlimab 1000 mg, or placebo, every 6 weeks for up to 3 years. Adverse events (AEs) were assessed according to Common Terminology Criteria for Adverse Events, version 4.03. The safety population included 487 patients who received ⩾1 dose of treatment (241 dostarlimab plus CP; 246 placebo plus CP). Treatment-emergent AEs were experienced by 100% of patients in both arms. TRAEs occurred in 97.9% of the dostarlimab arm and 98.8% of the placebo arm.The most common TRAEs occurred at similar rates between arms and were mostly low grade. IrAEs occurred in 58.5% of patients in the dostarlimab arm and 37.0% of patients in the placebo arm. Dostarlimab- or placebo-related irAEs were reported in 40.7% of patients in the dostarlimab arm and 16.3% of the placebo arm. The safety profile of dostarlimab plus CP was generally consistent with that of the individual components. Dostarlimab plus CP has a favorable benefit-risk profile and is a new standard of care for patients with primary advanced or recurrent EC. NCT03981796.