Background: We hypothesized that genetic variation of ATP-binding cassette subfamily B member 1 (ABCB1) that encodes P-glycoprotein (involved in the uptake of cyclosporin A [CsA]) contributes to trough drug concentrations and thereby to CsA's immunosuppressive and toxic effects.
Methods: Three hundred thirty-seven adult heart transplant recipients were studied retrospectively. White recipients receiving CsA at month 3 and years 1 to 5 after transplantation (n=192, 168, 156, 130, 95, and 74, respectively) were then studied with respect to ABCB1 genotype or haplotype and CsA disposition. Genotyping was performed using a gel-based polymerase chain reaction method. Dose- and weight-adjusted CsA trough concentrations ([microg/L]/[mg/kg]), time to first endomyocardial biopsy-proven acute rejection episode (grade>or=3A), weaning from steroids at 1 year, and renal function at 1 year posttransplant were measured.
Results: An association between dose- and weight-adjusted CsA trough concentrations and ABCB1 haplotypes was found, with 12/1236, 21/2677, 26/3435 CC/GG/CC individuals having significantly higher concentrations than TT/TT/TT individuals at years 1 and 5 (68.9+/-26.9 vs. 54.9+/-19.5 and 70.6+/-35 vs. 50.0+/-12.2 [microg/L]/[mg/kg] P<0.05, respectively) There was no difference in the incidence of acute rejection, steroid weaning, or renal impairment between the genotype or haplotype groups.
Conclusions: The association of ABCB1 12/1236, 21/2677, and 26/3435 CC/GG/CC haplotype with increased CsA dose- and weight-adjusted CsA trough concentrations in this group of adult white heart transplant recipients was not consistent over time and had no effect on the incidence of acute rejection or on the development of renal impairment.