The Absorption, Distribution, Metabolism, and Excretion of Binimetinib Following a Single Oral Dose of [

Binimetinib is a MEK1/2 inhibitor particularly active in cells harboring activating mutations in the MAP kinase pathway, especially in BRAF and NRAS. Binimetinib, in combination with encorafenib, has received marketing approval in several jurisdictions for the treatment of patients with BRAF V600E or V600K mutant melanoma. The absorption, distribution, metabolism, and excretion of binimetinib were evaluated by administering a carbon 14-labeled binimetinib 45 mg dose (containing 40 μCi of radiolabeled material) to 6 healthy male participants. A total of 62.3% of the radioactivity was eliminated in the feces, while 31.4% was eliminated in the urine. The overall recovery of radioactivity in the excreta for all 6 participants was 93.6% (3.27%), indicating that good mass balance was achieved. The total percentage of the dose in the excreta of all metabolites containing the N-demethylation clearance of binimetinib by CYP1A2 and CYP2C19 was approximately 17.8%. The contribution of direct glucuronidation to the clearance of binimetinib was estimated to be 61.2% and represented the majority of the clearance. Additionally, excretion of unchanged binimetinib into the urine was estimated to have contributed 6.9% to the overall clearance. Based on study results, binimetinib is at least ≈ 50% absorbed, but based on its PK properties and because its glucuronide conjugates are unstable in the GI tract, absorption is thought to be significantly higher.