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.

Eligibility Criteria:
Inclusion Criteria:

* Recipients of first kidney transplants (deceased or living donor) with stable allograft function
* 6 or more months after transplantation
* Currently on a stable dose of twice-daily tacrolimus and mycophenolate mofetil (MMF) or enteric coated mycophenolic acid (EC-MPA)± corticosteroids for a minimum of 6 months prior (patient has remained on a dosing that has changed no greater than ± 0.5mg/dose for a minimum of 4 months)
* Ability to comply with study procedures for the entire length of the study
* Patient and/or parent/legal guardian has been informed about the study survey and has signed an informed consent form.

Exclusion Criteria:

* Detectable donor specific anti-HLA antibody prior to enrollment (pre- or post-transplant)
* Actively being treated for an episode of biopsy proven acute cellular rejection (ACR) (Banff 1A or greater)
* Post-transplant history of biopsy proven ACR (Banff 1B or greater) or antibody mediated rejection (AMR)
* Currently receiving, planning to receive, or received within 7 days prior to study enrollment any drug interacting or interfering with tacrolimus metabolism (azole antifungals, erythromycin, clarithromycin, diltiazem, protease inhibitors, statins, grapefruit juice, rifampin or anti-seizure medications shown to interact with tacrolimus)
* Currently receiving an mTOR inhibitor (sirolimus, everolimus)
* Gastrointestinal illness that might affect the absorption of tacrolimus
* Unable or unwilling to complete study survey questionnaire
* Professional care taker is responsible for dispensing subject's medication
* Recipient of HLA identical or zero HLA mismatched organ transplant
* Documented history of medication non-adherence following transplantation prior to enrollment