Efficacy and Safety of Immunosuppression Withdrawal in Pediatric Liver Transplant Recipients: Moving Towards Personalized Management

Background and aims Tolerance is transplantation's holy grail as it denotes allograft health without immunosuppression and its toxicities. Our aim was to determine, among stable long-term pediatric liver transplant recipients, the efficacy and safety of immunosuppression withdrawal to identify operational tolerance. Approach and results We conducted a multi-center, single-arm trial of immunosuppression withdrawal over 36-48 weeks. Liver tests were monitored biweekly (year 1), monthly (year 2) and bimonthly (years 3-4). For-cause biopsies were done at investigators' discretion but mandated when alanine aminotransferase or gamma glutamyl transferase exceeded 100U/L. All subjects underwent final liver biopsy at trial end. The primary efficacy endpoint was operational tolerance, defined by strict biochemical and histological criteria 1 year after stopping immunosuppression. Among 88 subjects (median age 11 years; 39 boys; 57 deceased donor grafts), 33 (37.5%; 95%CI 27.4%, 48.5%) were operationally tolerant, 16 were non-tolerant by histology (met biochemical but failed histological criteria) and 39 were non-tolerant by rejection. Rejection, predicted by subtle liver inflammation in trial entry biopsies, typically (n=32) occurred at ≤32% of the trial entry immunosuppression dose and was treated with corticosteroids (n=32) and/or tacrolimus (n=38) with resolution (liver tests within 1.5X baseline) for all but 1 subject. No death, graft loss, or chronic, severe, or refractory rejection occurred. Neither fibrosis stage nor the expression level of a rejection gene set increased over 4 years for either tolerant or non-tolerant subjects. Conclusions Immunosuppression withdrawal showed that 37.5% of selected pediatric liver transplant recipients were operationally tolerant. Allograft histology did not deteriorate for either tolerant or non-tolerant subjects. The timing and reversibility of failed withdrawal justifies future trials exploring the efficacy, safety, and potential benefits of immunosuppression minimization.