Background: LEN, a multikinase VEGFR inhibitor, plus everolimus is approved for advanced RCC after prior VEGF-targeted therapy. PEMBRO, an anti-PD-1 antibody, plus axitinib is approved as first-line therapy of advanced RCC. We report phase 2 results of the RCC cohort of a phase 1b/2 trial (Study 111/KEYNOTE-146) of LEN + PEMBRO in patients (pts) who progressed after ICI therapy. Methods: We performed a multicenter, open-label study of pts with mccRCC, who previously had disease progression by RECIST (confirmed ≥ 4 weeks later) during or following ICI therapy. Pts had measurable disease by immune-related RECIST, and ≥ 1 prior therapy. Pts received LEN 20 mg orally once daily plus PEMBRO 200 mg IV every 3 weeks until disease progression or toxicity. Tumor assessments were performed every 6 weeks (until week 24), then every 9 weeks. The primary endpoint was objective response rate (ORR) at Week 24 by irRECIST. Results: 104 pts were enrolled. At data cutoff (January 12, 2020), 71 (69%) pts were still on study treatment. Most pts had ≥2 prior anticancer regimens (58%). 91 of 104 pts were evaluable for response at Week 12 (13 pts NE at Week 12); 46 of 91 pts achieved a confirmed partial response for an ORR of 51% (Table). Median progression-free survival (PFS) was 11.7 months and median duration of response (DOR) was 9.9 months. The most common treatment-related adverse events (TRAEs) were fatigue (49%), diarrhea (44%), proteinuria (37%), hypertension (31%), nausea (31%), dysphonia (29%), stomatitis (29%), and arthralgia (27%). There was 1 grade 5 TRAE (upper gastrointestinal hemorrhage). 43% of pts required dose reduction and 12% of pts discontinued treatment due to TRAEs. Response and safety data will be updated to include all pts evaluable at an April 9, 2020 cut-off. Conclusions: LEN + PEMBRO demonstrated promising antitumor activity in pts with mccRCC with disease progression following ICI therapy. No new safety signals were detected. Efficacy outcomes by investigator review per irRECIST. Clinical trial information: NCT02501096.

^aPatients followed for ≥12 weeks for response evaluation ^bComplete response + partial response + stable disease (duration ≥ 5 weeks) ^cTotal n as of data cutoff