A Phase Ib/II Study of the BRAF Inhibitor Encorafenib Plus the MEK Inhibitor Binimetinib in Patients with -mutant Solid Tumors.

PURPOSE

This open-label, dose-finding phase Ib/II study reports the safety and activity of the first combination use with BRAF inhibitor (BRAFi) encorafenib plus MEK inhibitor (MEKi) binimetinib in patients with V600E-mutant solid tumors.

PATIENTS AND METHODS

In phase I, the recommended phase 2 doses (RP2D) were established (primary objective). In phase II, the clinical activity of the combination at the RP2D was assessed (primary objective) in patients with -mutant metastatic colorectal cancer (mCRC), BRAFi-treated -mutant melanoma, and BRAFi-naïve BRAF-mutant melanoma.

RESULTS

A total of 126 patients with mutant solid tumors were enrolled (phase I: 47 patients; phase II: 79 patients). The RP2D was encorafenib 450 mg once daily plus binimetinib 45 mg twice daily and pharmacokinetic data suggest that drug exposures of each agent were similar in combination compared with single-agent studies. In the phase II cohorts, confirmed responses were seen in two of 11 (18%) evaluable patients with mCRC, 11 of 26 (42%) evaluable patients with BRAFi-pretreated melanoma, and 28 of 42 (67%) BRAFi-naïve patients with melanoma. The most common grade 3/4 adverse event in phase II was increased alanine aminotransferase.

CONCLUSIONS

The combination of encorafenib (450 mg) plus binimetinib (45 mg) showed acceptable tolerability and encouraging activity in patients with V600-mutant tumors, which led to the dose selection for the melanoma COLUMBUS study. The safety profile of the combination was consistent with other approved BRAFi plus MEKi regimens, with several differences, including lower rates of dose-limiting pyrexia, arthralgia, and photosensitivity.