*Purpose: The purpose of this study was to compare outcomes in liver transplant patients maintained on standard calcineurin inhibitor (CNI) therapy with tacrolimus versus those converted to a CNI-free regimen with sirolimus.

*Methods: This single center, retrospective study evaluated outcomes in liver transplant patients from January 1, 2015 to June 10, 2020 at the Emory Transplant Center. Inclusion criteria for the study included liver transplant recipients who were 18 years or older and either maintained on tacrolimus or converted to sirolimus. The two-cohort design of this study included an intervention group composed of patients undergoing conversion therapy from tacrolimus to sirolimus and a control group consisting of matched patients maintained on tacrolimus therapy. The primary endpoint was estimated glomerular filtration rate (eGFR) at 6- and 12-months post-transplant.

*Results: Of the 1452 patients that met inclusion criteria, 244 patients underwent conversion from tacrolimus to sirolimus. Tacrolimus patients were matched to sirolimus patients based on transplant indication, age, and renal function. As a result, the study included a total of 488 patients. Baseline characteristics were similar between groups. The mean age of patients was 61 years, and a majority of patients were Caucasian. The leading indications for transplant included hepatitis C, alcoholic cirrhosis, nonalcoholic steatohepatitis (NASH), and hepatocellular carcinoma. The mean eGFR at baseline was 67 mL/min/1.73m2 for the tacrolimus group and 60 mL/min/1.73m2 for the sirolimus group. At 6 months post-transplant, the mean eGFR for the tacrolimus group was 61 mL/min/1.73m2 compared to 54 mL/min/1.73m2 in the sirolimus group. Additionally, at 12 months post-transplant the mean eGFR for the tacrolimus group was 62 mL/min/1.73m2, while the mean eGFR for the sirolimus group was 57 mL/min/1.73m2. A greater decline in eGFR from baseline to 12 months was observed in patients maintained on tacrolimus at 5 mL/min/1.73m2 compared to patients switched to sirolimus at 3 mL/min/1.73m2. Biopsy proven acute rejection was observed more frequently in sirolimus patients at 15% compared to tacrolimus patients at 12%. The sirolimus group also experienced greater increases in total cholesterol, triglycerides, and blood pressure at 12 months.

*Conclusions: Overall renal function as measured by eGFR was greater for patients maintained on standard CNI therapy post-transplant; however, a greater decline in eGFR from baseline to 12 months occurred in the tacrolimus group. Alternatively, graft rejection was observed more frequently in the sirolimus group when compared to tacrolimus. Previous studies among kidney transplant recipients have shown that conversion from tacrolimus to sirolimus resulted in renal recovery, however additional studies are needed to determine the potential benefits of this conversion therapy in liver transplant recipients.

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