Atezolizumab (PD-L1) + bevacizumab (VEGF) posts 33.9% ORR in platinum-pretreated recurrent/metastatic endometrial cancer

Atezolizumab is an anti–PD-L1 immune checkpoint inhibitor and bevacizumab is an anti-VEGF monoclonal antibody; this Phase 2 open-label, multicenter, single-arm study treated ICI-naïve recurrent/metastatic endometrial cancer after platinum therapy (NCT03526432) with atezolizumab 1,200mg + bevacizumab 15mg/kg q3w. Among response-evaluable patients (n=56; pMMR n=45, dMMR n=7), ORR was 33.9% (5 CR, 14 PR) with median DOR 16 months; median PFS was 8.8 months and median OS was 41.6 months, with 63% progression-free at 6 months. Grade 3/4 AEs were led by hypertension (21.5%), fatigue (7.7%), and diarrhea (7.7%)—a profile that looks more “bevacizumab-like” than lenvatinib+pembrolizumab (KEYNOTE-775: ORR ~31.9% and median PFS 6.6 months in pMMR, but with substantial Grade ≥3 toxicity and frequent dose modifications/discontinuations), while dMMR patients still have a strong single-agent ICI benchmark (e.g., dostarlimab ORR ~43.5% in GARNET). Peripheral blood profiling suggested early immune-escape biology in non-responders (expansion of PD-L1+CD16+ monocytes, ICOS+ Tregs, and Fas+CD27+ central memory CD8+ T cells).