*Purpose: Early therapeutic tacrolimus levels have been associated with improved outcomes in renal transplant recipients while lower exposure to tacrolimus during the first week of kidney transplantation has been associated with early acute cellular rejection (ACR) post-transplant. These findings have yet to be elucidated utilizing extended-release tacrolimus (Envarsus XR®, LCP-Tac). Beginning in December 2015, our center instituted a protocol change moving to de novo use of LCP-Tac. The objective of this study is to assess the relationship between achievement of therapeutic tacrolimus levels at POD7 and the incidence of rejection.

*Methods: We performed a retrospective cohort analysis of adult kidney transplant recipients at a single center from 1/2015 to 6/2017 who received LCP-Tac-and remained on the same formulation for the first year post-transplant. Patients were divided into two groups based on achievement of therapeutic tacrolimus levels within 1 week post-transplant (POD7). Subtherapeutic tacrolimus level at POD7 (Sub-Goal) is defined as less than 7 ng/mL. Per our institution’s protocol, goal tacrolimus levels are 7-10ng/mL in the first 30 days post-transplant. The primary outcome was biopsy-proven acute cellular rejection in the first post-transplant year. Secondary outcomes include incidence of antibody mediated rejection, graft loss, and GFR and creatinine at 1, 3, and 6 months post-transplant.

*Results: Results: A total of 579 kidney transplants were performed between January 2015 and June 2017 and 231 were included in this study. 137 patients were in the Sub-Goal group and 94 were in the Met-Goal group. In total 10 patients (4.3%) experienced the primary endpoint which occurred in 6 (5.2%) of patients in the Sub-Goal arm and 4 (5.3%) patients in the Met-Goal arm (p = 1.0). There were no differences in antibody mediated rejection (2.9% vs. 3.2%, p=0.742) or graft loss (0.7% vs. 3.2%, p=0.307) in the Sub-Goal and Met-Goal groups, respectively. As shown in Table 1, there were no differences in renal function at 1, 3, and 6 months between the groups excluding differences in creatinine at months 3 and 6.

Table 1

*Conclusions: In de novo kidney transplant recipients, subtherapeutic tacrolimus levels for patients utilizing LCP-Tac was not associated with a difference in incidence of rejection in the first year post transplant.

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