Introduction: Several tacrolimus to belatacept conversion protocols have been described in the literature using various forms of tapering tacrolimus over days to weeks. Biopsy proven acute rejection (BPAR) post conversion ranged from 3-33%. The purpose of this study was to assess short-term efficacy of stopping tacrolimus at belatacept initiation while using a more reduced initial phase regimen than described previously in patients within 6 months of transplant.
Methods: A single-center retrospective chart review was conducted in renal transplant recipients (RTRs) converted to belatacept from tacrolimus between January 1, 2021 to March 31, 2022. Kidney transplant only patients were included if 18 years or older and converted to belatacept without tacrolimus tapering. Patients were excluded if started on de novo regimen or if patient continued on tacrolimus while on belatacept.  Belatacept was dosed at 5 mg/kg IV every two weeks for three doses if patients were within 6 months of transplant, or times five doses if transplanted 6 months or more from conversion prior to starting the maintenance phase. Standard induction protocol included anti-thymocyte globulin and methylprednisolone. Primary outcomes include BPAR, graft loss and patient survival within 6 months of conversion. Secondary outcomes included the incidence of antibody-mediated rejection (AMR), T-cell mediated rejection, CMV viremia, BK viremia, COVID-19 infection, and changes in serum creatinine and eGFR from the time of conversion and at 6 month post-conversion.
Results: Twenty-eight RTRs met criteria, with the majority converted within 6 months of transplant (92.9%). Three patients (10.7%) had BPAR, 2 had graft loss (7.1%), with 92.8% patient survival at 6 months. Of those with BPAR, all had cellular rejection and no AMR. The two patients with graft loss were due to infections (aspergillosis and COVID-19). Five patients developed CMV viremia, none had BK viremia and 6 (21.4%) had COVID-19. 6 months after conversion, the mean serum creatinine decreased by 1 mg/dl (from 4.2 mg/dl [4-10.0] to 3.2 mg/dL [1.39-10.71]) and the eGFR by CKD-EPI formula improved by 7.5 ml/min (from 21.7 mL/min/1.73m2 (range of 5-55) to 29.2 mL/min/1.73m2 [6-61] ).
Conclusions: Herein we describe a novel approach to converting kidney transplant patients from tacrolimus to belatacept without tapering tacrolimus and using fewer initial phase doses than standard in off-labeling regimens described previously with comparable outcomes.