Abstract
Mavacamten is a potential inducer of cytochrome P450 (CYP) 3A4 and could reduce the effectiveness of concomitant drugs that are metabolized by CYP3A4, such as midazolam. This study aimed to determine if repeat doses of mavacamten achieving clinically relevant exposures affected midazolam exposure. This was a single-center, open-label study in healthy participants. Participants received: on day 1, midazolam 5 mg; on days 2-3, mavacamten 25 mg; on days 4-16, mavacamten 15 mg; and on day 17, mavacamten 15 mg and midazolam 5 mg. Plasma concentrations of mavacamten, midazolam, and the midazolam metabolite 1'-hydroxymidazolam were measured. A physiologically based pharmacokinetic (PBPK) model was used to simulate the effect of mavacamten-mediated CYP3A4 induction on midazolam exposure by CYP2C19 phenotype. Thirteen adult participants were enrolled (46.2% were female; mean [SD] age: 34.0 [9.0] years). Compared with midazolam alone, midazolam coadministered with mavacamten decreased the maximum observed plasma concentration (C(max)), area under the drug concentration-time curve (AUC) from time zero to infinity (AUC(0-inf)), and AUC from time zero to last measurable concentration (AUC(0-last)) for midazolam by 7%, 13%, and 24%, respectively; for 1'-hydroxymidazolam, AUC(0-inf) and AUC(0Ȁlast) increased by 20% and 11%, respectively. Ten participants experienced adverse events and the majority were mild in severity. The PBPK model predicted the clinical trial data well. The PBPK simulation assessed that the overall impact of mavacamten on midazolam C(max) and AUC was predicted to be weak regardless of CYP2C19 phenotype. At clinically relevant exposures, mavacamten had a negligible effect on midazolam exposure.