Introduction/Background In the phase 3 RUBY trial (NCT03981796) in patients with primary advanced or recurrent endometrial cancer (pA/rEC) dostarlimab+carboplatin/paclitaxel significantly improved PFS versus carboplatin/paclitaxel alone in the mismatch repair deficient/microsatellite instability-high (HR 0.28) and overall populations (HR 0.64) with a favourable OS trend (HR 0.64). Here, we report on safety for the RUBY trial.
Methodology Patients with pA/rEC were randomised 1:1 to dostarlimab 500 mg, or placebo, plus carboplatin AUC 5 and paclitaxel 175 mg/m2 Q3W for 6 cycles, followed by dostarlimab 1000 mg, or placebo, Q6W for up to 3 years. Adverse events (AEs) were assessed according to CTCAE v4.03.
Results The safety population included 487 patients who received ≥1 dose of treatment (241 dostarlimab+carboplatin/paclitaxel; 246 placebo+carboplatin/paclitaxel). Treatment-emergent adverse events (TEAEs) were experienced by 100% of patients; 70.5% of the dostarlimab arm and 59.8% of the placebo arm experienced grade ≥3 TEAEs (table 1). Median time to TEAE was 2.0 days in the dostarlimab+carboplatin/paclitaxel arm and 2.5 days in the placebo+carboplatin/paclitaxel arm. TEAEs led to discontinuation in 23.7% of the dostarlimab+carboplatin/paclitaxel arm and 16.7% of the placebo+carboplatin/paclitaxel arm. Higher rates of discontinuation were reported during the chemotherapy phase (cycles 1–6) versus the monotherapy phase (cycles ≥7). TEAEs led to discontinuation of dostarlimab or placebo in 17.4% and 9.3% of patients (table 1). Discontinuation rates of carboplatin or paclitaxel were similar between arms. Immune-related AEs related to dostarlimab or placebo were reported in 38.2% of the dostarlimab arm and 15.4% of the placebo arm. Five deaths were reported in the dostarlimab arm; 2 were related to dostarlimab.
Conclusion The safety profile of dostarlimab+carboplatin/paclitaxel was consistent with that of the individual components. The addition of dostarlimab did not compromise the completion rate of chemotherapy. Dostarlimab+carboplatin/paclitaxel has a favourable benefit-risk profile that makes it a valuable treatment option for patients with pA/rEC.
Disclosures This study (NCT03981796) was sponsored by GSK, Waltham, MA, USA.
Third-party medical writing support Writing and editorial support, funded and coordinated by GSK (Waltham, MA, USA), was provided by Shannon Morgan-Pelosi, PhD, and Mary Wiggin of Ashfield MedComms, an Inizio company.
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