Co-Administration of Mavacamten and Tacrolimus in a Renal Transplant Recipient With Obstructive Hypertrophic Cardiomyopathy.

BACKGROUND

Mavacamten is a cytochrome P450 (CYP)3A4 inducer with a product label recommending careful monitoring alongside CYP3A4 substrates. Data characterizing its interaction with tacrolimus, a narrow-therapeutic-index immunosuppressant and CYP3A4 substrate, are lacking.

CASE SUMMARY: A 62-year-old woman kidney transplant recipient with symptomatic obstructive hypertrophic cardiomyopathy was started on mavacamten 5 mg daily. Over 5 months, serial monitoring showed stable, therapeutic tacrolimus troughs (5.9-7.8 ng/mL) without dosage adjustments, alongside significant clinical improvement in obstructive symptoms.

DISCUSSION: This case uniquely details the longitudinal pharmacokinetic interaction between mavacamten and tacrolimus. This is highly relevant because pharmacokinetic models suggest CYP3A4 induction is dose-dependent; thus, safety demonstrated at 5 mg may not apply to higher regimens like 15 mg.

TAKE-HOME MESSAGES: Low-dose mavacamten and tacrolimus coadministration is feasible. However, rigorous tacrolimus therapeutic drug monitoring remains essential, especially during mavacamten dose escalation.