Abstract 3895: A phase I-II pharmacokinetic drug-drug interaction evaluation of oral palbociclib in combination with vemurafenib in patients suffering metastatic melanoma with BRAF V600 mutated and CDKN2A loss & expression of Rb
Authors: Huguet Samuel , Lesimple Thierry , Geraud Arthur , Amini-Adle Mouna , Dutriaux Caroline , Meda Laetitia Da , Capelle Florence , Ghrieb Zineb , Mourah Samia , Madar Olivier , Bouton Didier , Resche-Rigon Mathieu , Lebbe Celest , Rezai Keyvan 
Published: August 2019

Background: A novel combination of vemurafenib (VM), a selectif inhibitor of BRAF V600 mutated protein + oral palbociclib (Palbo) a highly selective reversible oral inhibitor of cyclin-dependent kinases (CDK) 4 and 6, could provide a synergistic antitumor activity in patients with metastatic melanoma harbouring BRAF V600 mutation and CDKN2A loss. VM has been shown to be an inductor of CYP3A4 which is also mainly involved in Palbo metabolism.

In this study we investigated the potential pharmacokinetic (PK) drug-drug interactions (DDI) related to the association of VM and Palbo.

Methods: metastatic melanoma harbouring BRAF V600 mutation and CDKN2A loss patients were treated with a 14 days on followed by 7 days off dosing schedule of Palbo + continuous bid dosing of VM. Dose levels [DL, Palbo (mg/day)/VM (mg/bid)] ranged from 25/720 to 200/960. For PK analysis, 7 time point samples were collected on D1C1, D21C1, and D7C2, for Palbo and VM assays. Plasma concentrations of Palbo and VM, were measured using ultra high performance liquid chromatography (UHPLC) coupled with tandem mass spectrometry validated methods.

Population PK (PPK) was modeled using a non linear mixed effect model program (Monolix version 2018r) by computing the maximum likelihood estimator of the parameters without any approximation of the model (no linearization). The following parameters were calculated absorption constant (Ka); apparent distribution volume (V/F); apparent clearance (CL/F)

Results: A total of 18 patients were treated by the combination of Palbo + VM. VM and palbo plasma concentrations were measured in 236 and 275 blood samples respectively. A one-compartment open model with linear elimination adequately described Palbo concentration-time courses. The inter-individual variabilities (ISV) could be well estimated for all stuctural parameters. The PPK parameters obtained for the structural model were: Ka = 0.791 h-1, CL/F=76.0L/h, V1/F=2830 L. Albuminemia had a significant impact on palbo CL. A one-compartment model adequately fitted the VM plasma concentration-time data. The PPK parameters were CL/F=0.133 L/h, V/F=83.6 L and Ka has been fixed at 0.2 h-1. Body weight (BW) was the best size descriptor when VM CL and V terms were normalized to a mean BW of 70 Kg according to an allometric scaling rule.

Conclusions: The PPK modeling satisfactorily described the plasma Plabo and VM time-concentration curves in patients. The main covariate effect was related to BW and albuminemia. There is no significant evidence for drug-drug PK interaction between Palbo and VM. PK-PD modeling will be performed.

Citation Format: Samuel Huguet, Thierry Lesimple, Arthur Geraud, Mouna Amini-Adle, Caroline Dutriaux, Laetitia Da Meda, Florence Capelle, Zineb Ghrieb, Samia Mourah, Olivier Madar, Didier Bouton, Mathieu Resche-Rigon, Celest Lebbe, Keyvan Rezai. A phase I-II pharmacokinetic drug-drug interaction evaluation of oral palbociclib in combination with vemurafenib in patients suffering metastatic melanoma with BRAF V600 mutated and CDKN2A loss & expression of Rb [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3895.