Comparison of the Cognitive and Motor Effects of Treatment Between an Immediate- and Extended-release Tacrolimus (Envarsus® XR) Based Immunosuppression Regimen in Kidney Transplant Recipients

Between four (4) months and 14 months after receiving a kidney transplant and, per standard of care (SOC), having been placed on an immediate-release (IR) tacrolimus immunosuppressant regimen, participants in this study will undergo cognitive and motor function testing and have a blood sample collected (BASELINE). Half of the participants will then be randomly converted to extended-release (XR) tacrolimus (Envarsus® XR) while the other half will remain on IR tacrolimus for the duration of the study. Both the IR and XR groups will repeat the cognitive and motor function testing and have a blood sample collected at 6, 12, and 24 weeks Post-BASELINE. A practice version of the cognitive and motor function tests will be administered no more than 60 days prior to the baseline visit (Pre-BASELINE). Alternate versions of the cognitive and motor tests will be used at each Post-BASELINE testing session to control for possible practice effects. The primary objective is to compare the effect of treatment with an immediate-release tacrolimus to an extended-release tacrolimus (i.e., Envarsus® XR) immunosuppressive regimen on cognitive and motor function in kidney transplant recipients. The secondary objective is to determine the factors that explain inter-individual variability in cognitive response. Pharmacokinetic and demographic factors will be explored. Variability in cognitive response between individuals can be large. A population approach (nonlinear, mixed effects) will be used. Measurement of drug concentration will be the dependent variable.