The oral HIF-2 α inhibitor MK-6482 in patients with advanced clear cell renal cell carcinoma (RCC): Updated follow-up of a phase I/II study.
Authors: Todd Michael Bauer, Toni K. Choueiri, Kyriakos P. Papadopoulos, Elizabeth R. Plimack, Jaime R. Merchan, David F. McDermott, M. Dror Michaelson, Leonard Joseph Appleman, Sanjay Thamake, Rodolfo F. Perini, Eric Kristopher Park, Eric Jonasch
Journal: Journal of Clinical Oncology (2021)

273 Background: Clear cell RCC (ccRCC) accounts for ~70% of kidney cancer cases in the US. Several first-line therapies are approved for ccRCC, but few patients respond completely and most progress within 5-11 mo. A key oncogenic driver in RCC is the transcription factor hypoxia-inducible factor 2α (HIF-2α). MK-6482 is a small molecule HIF-2α inhibitor that blocks the heterodimerization of HIF-2α with HIF-1β, inducing tumor regression in mouse xenograft RCC models. Updated data presented here include additional follow-up from the expansion cohort of patients with ccRCC from the first-in-human phase 1/2 study of MK-6482 in advanced solid tumors (NCT02974738). Methods: Patients were aged ≥18 y with advanced ccRCC, received ≥1 prior therapy, and had RECIST v1.1 measurable disease, ECOG status 0 or 1, adequate organ function, and life expectancy ≥6 mo. They received 120 mg of MK-6482 orally once daily. Tumors were assessed at baseline, within 7 days before week 9, and then every 8 weeks; response was assessed using RECIST v1.1. The primary end point was safety. Secondary end points included ORR, duration of response (DOR), and PFS. Results: Fifty-five patients with ccRCC were treated with MK-6482 120 mg (52 in expansion and 3 in dose-escalation cohorts). The median number of prior therapies was 3 (range 1-9). Forty-two patients (81%) previously received PD-1/L1 inhibitors and 48 (92%) previously received VEGF inhibitors. Thirteen patients (24%) were classified as favorable risk and 42 (76%) as intermediate or poor risk per IMDC criteria. With a median follow-up of 28 mo, the most common all-grade, all-cause AEs &gt;30% were anemia (76%), fatigue (71%), dyspnea (49%), nausea (36%), cough (31%), and hypoxia (31%). Anemia (27%) and hypoxia (16%) were the most common grade 3 AEs. Two patients (4%) experienced grade 4 AEs, and 4 patients (7%) experienced grade 5 AEs. No grade 4 or 5 AEs were related to treatment. ORR was 25%, with 14 confirmed PRs. Thirty patients (55%) had SD, with a disease control rate (CR+PR+SD) of 80%. Median DOR was not reached; 77% had a response ≥6 mo. By IMDC risk, 4 of 13 patients with favorable risk had PR (ORR = 31%) and 10 of 42 with intermediate or poor risk had PR (ORR = 24%); disease control rate was 92% and 76%, respectively. Median PFS for the total population was 14.5 mo; 51% had a PFS of 12 mo. As of June 1, 2020, 33 patients (60%) discontinued because of PD and 2 (4%) because of AEs; 11 patients (20%) had ongoing treatment. Conclusions: MK-6482 remained well tolerated with a favorable safety profile and promising single-agent activity in patients with ccRCC for all IMDC risk groups after further follow-up. A phase III trial in a similar population is underway. Clinical trial information: NCT02974738 .