Drug Interactions between cobimetinib and sofosbuvir / velpatasvir

MONITOR: Coadministration with inhibitors of CYP450 3A4 and/or P-glycoprotein (P-gp) may increase the plasma concentrations of cobimetinib, which is a substrate of both the isoenzyme and the efflux transporter. In 15 healthy volunteers given a single 10 mg dose of cobimetinib with the potent CYP450 3A4 and P-gp inhibitor itraconazole (200 mg once daily for 14 days), mean cobimetinib peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 3.2- and 6.7-fold, respectively, compared to cobimetinib administered alone. Simulations using physiologically-based pharmacokinetic (PBPK) models suggest that steady-state concentrations of cobimetinib given at a reduced dose of 20 mg with short-term (less than 14 days) use of a moderate CYP450 3A4 inhibitor would be similar to steady-state concentrations observed following a 60 mg dose given alone.

MANAGEMENT: Caution is advised when cobimetinib is prescribed with CYP450 3A4 and/or P-gp inhibitors. Patients should be monitored for adverse effects such as diarrhea, nausea, vomiting, stomatitis, hemorrhage, cardiomyopathy, rash, photosensitivity, retinopathy, retinal vein occlusion, liver enzyme abnormalities and rhabdomyolysis, and the cobimetinib dosage adjusted accordingly or treatment discontinued as necessary.