Effect of CYP3A5, CYP3A4, and ABCB1 genotypes as determinants of tacrolimus dose and clinical outcomes after heart transplantation.

Background: Tacrolimus (Tac) is mainly metabolized by cytochrome P450 3A isoenzymes. In a cohort of heart transplant recipients, we investigated the effect of CYP3A5, CYP3A4, and ABCB1/MDR1 polymorphisms on Tac dose requirements and the risk of developing new-onset diabetes after transplantation (NODAT).

Methods: A total of 65 heart transplant recipients were genotyped for 3 single nucleotide polymorphisms (SNPs) in the CYP3A5 (SNP rs776746), CYP3A4 (SNP rs2740574), and ABCB1 (SNP rs104564). The mean Tac dose values were compared between the genotypes.

Results: CYP3A5 3 homozygotes (nonexpressers; n = 55, 85%) received significantly higher Tac dose compared with CYP3A5 1 carriers (expressers). No different NODAT frequencies were found between the genotypes.

Conclusions: The CYP3A5 polymorphism was the main determinant of Tac dose requirements among heart transplant recipients. This common functional polymorphism had no influence on the risk of developing NODAT.