ASCO GU 2020: A Phase I/II Study of the Oral HIF-2 α Inhibitor MK-6482 in Patients with Advanced Clear Cell Renal Cell Carcinoma (ccRCC)

San Francisco, CA ( Hypoxia-inducible factor (HIF)-2a is a transcription factor that is one of the most important drivers for the development and progression of clear cell renal cell carcinoma (ccRCC). MK-6482 is a first-in-class HIF-2a inhibitor that blocks the heterodimerization of HIF-2a with HIF-1B. Although it has previously been shown to induce regression in mouse xenograft ccRCC models, its efficacy in human patients with advanced ccRCC has yet to be evaluated.

Dr. Toni Choueiri presented the results from a first-in-human phase I/II study that evaluated the safety and efficacy of single-agent MK-6482 in patients with pretreated metastatic ccRCC. The study included 55 patients with advanced cc RCC who had all received at least 1 prior therapy. All patients were administered 120 mg of MK-6482 orally once daily. The primary endpoint assessed was safety. The secondary endpoints assessed were overall response rate (ORR), duration of response (DOR) and progression-free survival (PFS).

The study design was as follows:

ASCO GU 2020 MK 6482 study design

Of 55 patients enrolled, the median (range) number of prior therapies was 3 (1-9). Five/55 (9%) patients were favorable risk, 40/55 (73%) patients were intermediate risk, and 10/55 (18%) patients were poor risk by International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) criteria. With regards to the primary endpoint, at a median follow-up of 13 months, the most common all-grade, all-cause adverse events were anemia (75%), fatigue (67%), dyspnea (47%), nausea (33%), and cough (31%). The most common grade 3 adverse events were anemia (26%) and hypoxia (15%). No grade 4-5 drug-related adverse events were observed.

With regards to secondary endpoints, ORR was 24%. There were 13/55 (24%) patients with partial response (PR) and 0/55 (0%) with complete response (CR). Thirty-one (56%) patients had stable disease (SD). The disease control rate (CR+PR+SD) was 80%. Thirty-five/52 (67%) patients with baseline and postbaseline assessments were noted to have tumor shrinkage. Although median DOR was not yet reached, 81% of patients had [Symbol]6 months response per Kaplan-Meier estimate and 16 (29%) patients continued treatment beyond 12 months. Stratified by IMDC risk, 2/5 patients with favorable risk had PR (ORR = 40%), 10/40 patients with intermediate risk had PR (ORR = 25%), and 1/10 with poor risk had PR (ORR = 10%). The disease control rate was 100% for patients with favorable risk, 80% for patients with intermediate risk, and 70% for patients with high risk. Overall, the median PFS was 11 months, and the 12 month PFS rate was 49%. Stratified by IMDC risk, the median PFS was 16.5 months in patients with favorable risk, 11.0 months in patients with intermediate risk, and 6.9 months in patients with poor risk. During the study period, 2/55 (4%) discontinued treatment due to AE, and 30/55 (55%) discontinued treatment due to PD.

Dr. Choueiri concluded that MK-6482 is well tolerated with a favorable safety profile. Also, MK-6482 as a single agent is a promising treatment for patients with heavily pretreated ccRCC across all IMDC risk groups. Given the encouraging results of this study, a phase 3 trial evaluating the efficacy of MK-6482 in a similar population is underway.

Presented by: Toni K. Choueiri, MD, Chief of Lank Center for Genitourinary Oncology, Dana-Farber Cancer Institute,  Boston, Massachusetts

Written By: Ziho Lee, MD, Fellow in Advanced Robotic Oncology and Reconstruction, Temple University, Philadelphia, PA, Twitter: @ZLeeGU at the 2020 Genitourinary Cancers Symposium, ASCO GU #GU20, February 13-15, 2020, San Francisco, California