O018/#482 Updated Safety of Lenvatinib + Pembrolizumab Vs Treatment of Physician’s Choice in Patients with Advanced Endometrial Cancer: Study 309/Keynote-775

Objectives In patients with advanced endometrial cancer (aEC), lenvatinib + pembrolizumab (L+P) demonstrated statistically significant and clinically meaningful improvements in PFS, OS, and ORR versus treatment of physician’s choice (TPC) at first efficacy interim analysis. Efficacy was maintained with extended follow-up at the final prespecified data cutoff (1 March 2022). Here we report additional safety/tolerability analyses from the same final prespecified data cutoff. Methods Detailed methods have been published [Makker 2022]. Briefly, patients with aEC and 1 prior platinum-based chemotherapy regimen (up to 2 if 1 given in the neoadjuvant/adjuvant setting) were randomized (1:1) to receive lenvatinib 20 mg orally QD + pembrolizumab 200 mg IV Q3W or TPC (doxorubicin 60 mg/m2 IV Q3W or paclitaxel 80 mg/m2 IV QW [3-weeks-on/1-week-off]). We report safety data of patients who received treatment with 16 months of additional follow-up since the primary analysis. Results 794 Patients treated with L+P (n=406) or TPC (n=388) were included. Data for these patients regarding adverse events are shown in the table 1. Dose interruptions due to treatment-emergent adverse events were experienced by 71.9% of patients treated with L+P (lenvatinib: 61.6%; pembrolizumab: 52.5%; L+P: 32.5%) and by 28.4% of patients treated with TPC. Dose reductions were needed for 67.2% of patients who received lenvatinib and 12.6% of patients who received TPC. Treatment was discontinued by 39.2% of patients who received L+P (lenvatinib: 35.7%; pembrolizumab: 22.2%; L+P: 16.0%) and by 8.0% of patients who received TPC. Conclusions In patients with aEC, updated safety/tolerability results with L+P over extended time were generally consistent with the primary analysis from Study 309/KEYNOTE-775.