Envarsus XR® in Adolescent Renal Transplant Recipients

Adolescents commonly experience barriers to adherence that entail forgetfulness, distraction, poor planning, and scheduling problems. A once daily oral regimen may be superior to the current regimens that require twice daily dosing. It is currently unclear if Envarsus XR® would improve outcomes in adolescent organ transplant recipients. Each patient will receive tacrolimus (twice daily immediate release oral formulation) which they are using as part of their standard of care immunosuppressive regimen for a portion of the study and Envarsus XR® (a once daily extended-release oral tacrolimus formulation) for a portion of the study in a cross-over design. Besides the advantage to adherence behaviors, a sustained-release tacrolimus preparation may decrease burdensome side effects and increase quality of life. Following enrollment, each patient will be maintained in the study for 9 months.

This is a randomized, prospective, single-center, pilot study assessing once daily Envarsus XR® medication efficacy, adverse events, medication non-adherence, patient-reported outcomes, and abbreviated pharmacokinetics/ dose finding to evaluate a population of adolescent renal transplant recipients while on stable tacrolimus (twice daily) and then after conversion to Envarsus XR® to provide critical efficacy, safety, dose-finding, adherence, and patient reported outcome data that could lead to adoption of Envarsus XR® as a mainstay of pediatric/adolescent post-transplant immunosuppression.

Following randomization, and independent of the formulation of tacrolimus, each patient will have a "run-in" period of 14 days to optimize the dose to reach a tacrolimus trough level of 4 to 10 ng/ml.

• Drug Administration: After randomization (to either twice daily tacrolimus or once daily Envarsus ®) and the "run-in" period, patients will be continued on their assigned tacrolimus formulation for 4 months. He/she will then be then switched to the opposite tacrolimus formulation. Following the switch, there will be a 14 day run-in period to establish the optimal trough level (4-10 ng/ml) (analogous to the first run-in period) and then continued on that tacrolimus formulation for 4 months.
• Pharmacokinetics: Irrespective of whether a patient starts on Envarsus XR® after randomization or is switched to Envarsus XR® after 4 months of immediate release tacrolimus, the dose of Envarsus XR® will be determined by using a dose conversion ratio targeting 0.7 (but may range from 0.66-0.8 because of dosage strengths of Envarsus XR® dosing formulations) relative to the immediate release formulation that he/she was receiving as maintenance.