Binimetinib/Encorafenib Positive OS Data Released as FDA Weighs Melanoma Approval

Keith T. Flaherty, MD

Treatment with the BRAF inhibitor encorafenib and the MEK inhibitor binimetinib improved survival versus single-agent vemurafenib (Zelboraf) in patients with BRAF-mutant advanced, unresectable or metastatic melanoma, according to updated findings from the phase III COLUMBUS trial.

The combination of encorafenib at 450 mg daily and binimetinib at 45 mg twice daily reduced the risk of death by 39% versus vemurafenib monotherapy (hazard ratio [HR], 0.61; 95% CI 0.47-0.79; P <.001).¹ The median overall survival was 33.6 months versus 16.9 months, respectively.

The FDA is currently reviewing a new drug application supporting use of the encorafenib/binimetinib combination in this setting. Array BioPharma, the company developing the regimen, is specifically seeking approval for the combination at doses of binimetinib at 45 mg twice daily and encorafenib at 450 mg once daily. Under the Prescription Drug User Fee Act, the FDA is scheduled to make its decision by June 30, 2018.

“Many patients with BRAF-mutant melanoma still face significant challenges managing their disease, and there remains a substantial need for well-tolerated treatments that delay disease progression and improve overall survival,” Keith T. Flaherty, MD, Director of the Termeer Center for Targeted Therapy, Massachusetts General Hospital Cancer Center and Professor of Medicine, Harvard Medical School, said in a statement. "This data suggests that the combination of encorafenib and binimetinib may have the potential to become a meaningful new therapy for patients with advanced BRAF-mutant melanoma."

The full COLUMBUS trial included 921 patients with BRAF V600-mutant melanoma, with 577 in part 1 and 344 in part 2.² In part 1, patients were randomized in a 1:1:1 ratio to receive encorafenib at 450 mg daily plus 45-mg twice daily binimetinib (COMBO450; n = 192), encorafenib alone at 300 mg daily (n = 191), or 960-mg twice daily vemurafenib (n = 194). In part 2, patients were randomized 3:1 to encorafenib at 300 mg daily plus binimetinib a 45 mg twice daily (COMBO300; n = 258) or encorafenib alone at 300 mg daily (n = 88).

Patient characteristics were well balanced across treatment arms. The median age of patients ranged from 55 to 58 years and the majority had an ECOG performance status of 0 (~72%). LDH levels were greater than or equal to the upper limit of normal for about a third of patients and about two-thirds of patients had IVM1c tumor stage at study entry. Prior checkpoint inhibitors were received by 5% to 7% of patients, primarily ipilimumab.

Across the full 2-part study, the median progression-free survival (PFS) for patients treated with 300-mg encorafenib plus 45-mg binimetinib was 12.9 months compared with 9.2 months for patients receiving encorafenib alone (HR, 0.77; 95% CI, 0.61-0.97; P = .029). In those getting a larger 450 mg dose of encorafenib with 45-mg binimetinib, the median PFS was 14.9 versus 7.3 months with vemurafenib (HR, 0.54; 95% CI, 0.41-0.71; P <.001).

In part 2 of the study, the median PFS with COMBO300 was 12.9 months compared with 7.4 months with encorafenib (HR, 0.67; 95% CI, 0.41-0.78; P <.001). The objective response rate (ORR) was 66% with COMBO300 and the ORR was 50% with encorafenib alone. The complete response rate was 8% with COMBO300 and 3% with encorafenib monotherapy.

During his presentation of the COLUMBUS data at the 2017 ESMO Congress, lead investigator Reinhard Dummer, MD, from University Hospital Zurich, noted that encorafenib could be considered a second-generation BRAF inhibitor. The agent has a unique pharmacologic profile and is ATP-competitive, he noted. When compared with single-agent vemurafenib, encorafenib was superior for PFS (9.6 vs 7.3 months; HR, 0.68; 95% CI, 0.52-0.90; P = .007).

Binimetinib also appears to have unique characteristics. The agent, which is a selective allosteric, ATP-uncompetitive inhibitor of MEK1/2, has a shorter half-life than other MEK inhibitors, Dummer noted. This could lead to more rapid resolution of toxicity following dose interruptions, he added.

Nearly all patients in the trial experienced at least 1 adverse event (AE). Grade 3/4 AEs were experienced by 47% of patients in the COMBO300 group and for 63% of those treated with single-agent encorafenib across both part 1 and part 2. Grade 3/4 serious AEs were similar with COMBO300 and single-agent encorafenib (25% vs 28%). AEs leading to discontinuation occurred for 12% with COMBO300 and for 13% with encorafenib.

Fewer all-grade AEs were associated with COMBO300 versus single-agent encorafenib, except for diarrhea (28% vs 17%), increased CK (20% vs 1%), increased GGT (14% vs 11%), and increased ALT (11% v 4%). For COMBO450 and COMBO300, respectively, the most common BRAF/MEK-associated AEs were rash (23% and 15%), pyrexia (18% and 17%), retinal pigment epithelial detachment (13% and 9%), and photosensitivity (5% and 2%).

References

1. Encorafenib and Binimetinib Combination Treatment Demonstrates 33.6 Month Median Overall Survival (OS) in Patients with BRAF-Mutant Melanoma in Phase 3 COLUMBUS Trial. Array BioPharma. Published February 6, 2018. Accessed February 6, 2018. http://prn.to/2GU3BdI.
2. Dummer R, Ascierto PA, Gogas H, et al. Results of COLUMBUS Part 2: A phase 3 trial of encorafenib (ENCO) plus binimetinib (BINI) versus ENCO in BRAF-mutant melanoma. Presented at: 2017 ESMO Congress; Madrid, Spain; September 9-12, 2017. Abstract 1215O.