Exposure-Response Modeling and Simulation to Identify Optimal Mavacamten Posology When Coadministered with CYP3A4 and...

Area of Science:

• Pharmacology and Therapeutics
• Cardiology
• Drug Metabolism

Background:

• Mavacamten, a cardiac myosin inhibitor, is metabolized by CYP2C19 and CYP3A4.
• Current guidelines contraindicate coadministration with strong CYP3A4 or CYP2C19 inhibitors in obstructive hypertrophic cardiomyopathy (HCM).

Purpose of the Study:

• To assess the safety and efficacy of modified mavacamten dosing strategies during coadministration with strong CYP3A4 and strong/moderate CYP2C19 inhibitors.
• To evaluate the impact of these modifications on patient outcomes, including left ventricular ejection fraction (LVEF) and left ventricular outflow tract gradient (VLVOTg).

Main Methods:

• Population pharmacokinetic and exposure-response modeling were used to simulate 5000 virtual patients with obstructive HCM.
• Simulations evaluated both short-term (1-week) and long-term (chronic) coadministration scenarios.
• Safety was assessed by the proportion of patients with LVEF <50%, and efficacy by VLVOTg <30 mm Hg.

Main Results:

• A modified posology with a 2.5-mg starting dose and LVEF monitoring demonstrated similar safety profiles for CYP2C19 poor and ultrarapid metabolizers.
• Dose reductions were necessary for patients initiating inhibitor therapy, potentially delaying optimal efficacy.
• Stable mavacamten therapy could be maintained with dose reduction when inhibitors were initiated; short-term interruption led to transient VLVOTg increases without affecting LVEF.

Conclusions:

• Modified mavacamten dosing strategies can accommodate coadministration with CYP3A4 or CYP2C19 inhibitors in obstructive HCM patients.
• These adjustments are crucial for managing drug interactions while preserving safety and efficacy.
• Further research may refine dosing to optimize outcomes in this patient population.