Benedetta C Sallustio1,2, Benjamin D Noll3, Rong Hu4, Daniel T Barratt2, Jonathan Tuke5,6, Janet K Coller2, Graeme R Russ7, Andrew A Somogyi2. 1. Department of Clinical Pharmacology, Basil Hetzel Institute, The Queen Elizabeth Hospital, Woodville South, SA, 5011, Australia. 2. Discipline of Pharmacology, Adelaide Medical School, University of Adelaide, Adelaide, SA, 5000, Australia. 3. School of Pharmacy and Medical Sciences, University of South Australia, Australia, Adelaide, SA, 5000, Australia. 4. Department of Pharmacy, Guangzhou Women's and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China. 5. ARC Centre for Excellence for Mathematical and Statistical Frontiers, School of Mathematical Sciences, Adelaide, SA, 5000, Australia. 6. School of Mathematical Sciences, Adelaide, SA, 5000, Australia. 7. Central Northern Adelaide Renal and Transplantation Services, Royal Adelaide Hospital, Adelaide, SA, 5000, Australia.
Abstract
AIMS: Long-term use of the immunosuppressant tacrolimus is limited by nephrotoxicity. Following renal transplantation, the risk of nephrotoxicity may be determined more by allograft than by blood tacrolimus concentrations, and thus may be affected by donor CYP3A5 and ABCB1 genetics. Little is known regarding factors that determine tacrolimus intrarenal exposure. METHODS: This study investigated the relationship between trough blood (C0Blood ) and allograft (CGraft ) tacrolimus concentrations and tacrolimus dose, haematocrit, genetics, acute nephrotoxicity, rejection status, delayed graft function, and time post-transplant. C0Blood and CGraft were quantified in 132 renal transplant recipients together with recipient and donor CYP3A5 (rs776746) and ABCB1 3435 (rs1045642) genotypes. RESULTS: C0Blood ranged from 2.6 to 52.3 ng/mL and CGraft from 33 to 828 pg/mg tissue. Adjusting for dose, recipients who were CYP3A5 expressors had lower C0Blood compared to nonexpressors, whilst delayed graft function was associated with higher C0Blood . Linear regression showed that the significant predictors of CGraft were C0Blood (point-wise P = 7 × 10-10 ), dose (P = .004) acute nephrotoxicity (P = .002) and an interaction between C0Blood and acute tacrolimus nephrotoxicity (P = .0002), with an adjusted r2 = 0.35 and no contribution from donor or recipient CYP3A5 or ABCB1 genotype. The association between CGraft and acute nephrotoxicity depended on one very high CGraft (828 pg/mg tissue). CONCLUSIONS: Recipient and donor CYP3A5 and ABCB1 3435C>T genotypes are not determinants of allograft tacrolimus exposure in kidney transplant recipients. However, tacrolimus dose and C0Blood were significant predictors of CGraft , and the relationship between C0Blood and CGraft appeared to differ in the presence or absence of acute nephrotoxicity.
AIMS: Long-term use of the immunosuppressant tacrolimus is limited by nephrotoxicity. Following renal transplantation, the risk of nephrotoxicity may be determined more by allograft than by blood tacrolimus concentrations, and thus may be affected by donor CYP3A5 and ABCB1 genetics. Little is known regarding factors that determine tacrolimus intrarenal exposure. METHODS: This study investigated the relationship between trough blood (C0Blood ) and allograft (CGraft ) tacrolimus concentrations and tacrolimus dose, haematocrit, genetics, acute nephrotoxicity, rejection status, delayed graft function, and time post-transplant. C0Blood and CGraft were quantified in 132 renal transplant recipients together with recipient and donor CYP3A5 (rs776746) and ABCB1 3435 (rs1045642) genotypes. RESULTS: C0Blood ranged from 2.6 to 52.3 ng/mL and CGraft from 33 to 828 pg/mg tissue. Adjusting for dose, recipients who were CYP3A5 expressors had lower C0Blood compared to nonexpressors, whilst delayed graft function was associated with higher C0Blood . Linear regression showed that the significant predictors of CGraft were C0Blood (point-wise P = 7 × 10-10 ), dose (P = .004) acute nephrotoxicity (P = .002) and an interaction between C0Blood and acute tacrolimusnephrotoxicity (P = .0002), with an adjusted r2 = 0.35 and no contribution from donor or recipient CYP3A5 or ABCB1 genotype. The association between CGraft and acute nephrotoxicity depended on one very high CGraft (828 pg/mg tissue). CONCLUSIONS: Recipient and donor CYP3A5 and ABCB1 3435C>T genotypes are not determinants of allograft tacrolimus exposure in kidney transplant recipients. However, tacrolimus dose and C0Blood were significant predictors of CGraft , and the relationship between C0Blood and CGraft appeared to differ in the presence or absence of acute nephrotoxicity.