The tacrolimus metabolism affect post-transplant outcome mediating acute rejection and delayed graft function: analysis from Korean Organ Transplantation Registry data

Tacrolimus is a key drug in kidney transplantation (KT) with a narrow therapeutic index. The association between the tacrolimus metabolism rate and KT outcomes have not been investigated in large-scale multi-center studies. The Korean Organ Transplantation Registry (KOTRY) datasets were used. A total of 3456 KT recipients were analyzed. The tacrolimus metabolism rate was defined as blood trough concentration of tacrolimus (C₀) divided by the daily dose (D). The patients were grouped into fast, intermediate, or slow metabolizers by the C₀/D measured 6 months after transplantation. The slow metabolism group was associated with a 2.7 ml/min/1.73 m² higher adjusted estimated glomerular filtration rate (eGFR) at 6 months [95% confidence interval (C.I.) 1.2–4.3, P = 0.001], less acute rejection (AR) within 6 months [Odds ratio (OR) 0.744, 95% C.I. 0.585–0.947, P = 0.016], and less interstitial fibrosis and tubular atrophy [OR 0.606, 95% C.I. 0.390–0.940, P = 0.025]. Fast tacrolimus metabolism affected the 6-month post-KT eGFR through mediation of AR [natural indirect effect (NIE) −0.434, 95% C.I. −0.856 to −0.012, P = 0.044) and delayed graft function (DGF; NIE −0.119, 95% C.I. −0.231 to −0.007, P = 0.038). Slow tacrolimus metabolism was associated with better post-KT eGFR. AR and DGF were found to be significant mediators.