Pharmacokinetic Study of Tacrolimus and Mycophenolate Mofetil in Kidney Transplant Recipients With Hyperkalemia Receiving Patiromer

This is an open-label single center pharmacokinetic study of kidney transplant recipients with hyperkalemia receiving tacrolimus and MMF-based immunosuppression. Subjects will be screened for inclusion and exclusion criteria during the screening visit. There will be 2 study visits (visit 0 and visit 1) for each subject after successful screening. Visit 0 occurs within 14 days (± 3 days) after screening. Visit 1 occurs at 7 days (± 3 days) after visit 0. There will be 3 clinical visits (standard of care) after visit 1. A total of 6 visits are anticipated for this study. Standard diet for lunch and dinner will be provided to subjects during visit 0 and visit 1. Meals provided will be monitored in relationship to C0 and C12. During screening visit, blood tests for baseline BMP, aldosterone, magnesium, tacrolimus, DSA, and MMF will be obtained. If applicable, concomitant fludrocortiosone will be stopped prior to screening. During visit 0, tacrolimus levels will be drawn immediately before (0 hr) and at 8 intervals after dosing (1,2,3,4,5,6,9,12 hrs). MMF levels will be drawn immediately before (0 hr) and at 9 intervals after dosing (1,2,3,4,5,6,7,9,12 hrs). Basic metabolic profile and serum magnesium levels will be drawn immediately before tacrolimus dosing. Oral MMF and tacrolimus will be dosed at 8am ± 1hr. Enrollment is defined as the first day when subject receives patiromer treatment. Patiromer (8.4 grams) will be taken daily at 3 hours after oral tacrolimus and MMF dosing by subjects commencing 3 days (± 1 day) prior to visit 1. No tacrolimus or MMF dosing changes are allowed between visit 0 and 1. The addition of new concomitant drugs causing interactions with tacrolimus and MMF are prohibited between visit 0 and 1. During visit 1, subjects will follow the same protocol of blood draws as visit 0. Tacrolimus levels will be drawn immediately before (0 hr) and at 8 intervals after tacrolimus dosing (1,2,3,4,5,6,9,12 hrs). MMF levels will be drawn immediately before (0 hr) and at 9 intervals after MMF dosing (1,2,3,4,5,6,7,9,12 hrs). Basic metabolic profile and serum magnesium levels will be drawn immediately before tacrolimus dosing. Patiromer at 8.4 grams will be given 3 hrs after tacrolimus and MMF dosing. Oral MMF and tacrolimus will be dosed at 8am ± 1hr. All subjects will followup for clinical visits (2-4) with the PI or their transplant nephrologists after visit 1 according to schedule (see appendix for study visit events). Subjects will complete study by 30 days (± 7 days) after visit 0. Adjustment of patiromer dosing is at the discretion of PIs after visit 2. After completion of study visits, subjects will continue to follow with transplant clinic monthly for 2 months or sooner if clinically indicated per the discretion of the treating transplant nephrologist. After 2 months, clinic visits will be conducted per routine clinic schedule.