Population Pharmacokinetic Modeling of Encorafenib in Healthy Participants and Patients with BRAF V600-Mutant Solid Tumors: A Semi-mechanistic Autoinduction Model.

Abstract

Background and objective: Encorafenib is a potent and selective adenosine triphosphate-competitive BRAF V600-mutant kinase inhibitor. Encorafenib is approved for multiple indications in combination with binimetinib or cetuximab. This analysis aimed to develop a global population pharmacokinetics (popPK) model characterizing encorafenib disposition across tumor types.

Methods: The popPK analysis was based on nine phase 1 to 3 studies in participants with melanoma, colorectal cancer (CRC), non-small cell lung cancer, or other solid tumors, and healthy participants. A total of 1310 participants who received encorafenib as monotherapy or in combination were included. Nonlinear mixed effects modeling was performed using NONMEM v7.5.0. A semi-mechanistic enzyme turnover model was assessed to quantify the autoinduction effect. Stepwise covariate modeling using Perl-speaks-NONMEM (version 5.3.0) evaluated a broad range of covariates.

Results: A two-compartment model with first-order absorption and concentration-dependent autoinduction successfully characterized the concentration-time profile of encorafenib. Encorafenib apparent clearance (CL/F) was estimated to be 12.2 L/h after the first dose in a typical adult and increased by 186% to 35 L/h at steady state. This model indicates that maximum autoinduction is expected within 14 days of daily dosing (autoinduction half-life 64 h). Age and tumor type (melanoma, metastatic CRC, other [healthy, lung tumors, other solid tumors]) on CL/F and body weight on volume of distribution were significant covariates; these effects were not determined to be clinically significant.

Conclusions: This model successfully described the PK of encorafenib over time and across tumor types. No dose modifications are suggested on the basis of intrinsic or extrinsic factors evaluated.