Composite CYP3A (CYP3A4 and CYP3A5) phenotypes and influence on tacrolimus dose adjusted concentrations in adult...

Area of Science:

• Pharmacogenomics
• Transplant Medicine
• Drug Metabolism

Background:

• CYP3A5 genetic variants influence tacrolimus metabolism.
• The additional impact of CYP3A4 variants (e.g., *1B, *1G, *22) on tacrolimus pharmacokinetics remains debated.
• Tacrolimus (TAC) is a critical immunosuppressant post-heart transplantation.

Purpose of the Study:

• To investigate if combined CYP3A5 and CYP3A4 genotypes provide additional information on tacrolimus dose-adjusted trough concentrations (TAC C0/dose).
• To compare TAC C0/dose between different combined CYP3A phenotype groups in heart transplant recipients.
• To evaluate the impact of combined CYP3A genotypes on TAC dosing parameters like discharge dose and time to therapeutic range.

Main Methods:

• Retrospective cohort study of 177 heart transplant patients (2008-2020).
• Patients were categorized into combined CYP3A phenotype groups based on CYP3A5 and CYP3A4 genotypes.
• Tacrolimus dose-adjusted trough concentrations (TAC C0/dose) were analyzed at various time points post-transplant.

Main Results:

• Significant differences in TAC C0/dose were observed between combined CYP3A phenotype groups, persisting up to 6 months post-transplant.
• CYP3A5 nonexpressers with CYP3A4 *1B or *1G variants showed lower TAC C0/dose at 2 months compared to those with CYP3A4 *1/*1.
• Differences were noted in discharge TAC dose and time to therapeutic range, but not in time in therapeutic range.

Conclusions:

• Combined CYP3A phenotype interpretation, considering both CYP3A5 and CYP3A4, offers a more nuanced understanding of tacrolimus pharmacokinetics.
• This approach may enhance genotype-guided tacrolimus dosing strategies in heart transplant recipients.
• Further research could refine personalized tacrolimus therapy based on comprehensive CYP3A genotyping.