*Purpose: Renal function decline after liver transplant (LT) remains a significant issue. Using antithymocyte globulin (rATG) to delay tacrolimus (TAC) initiation may impact renal deterioration; however long term impact is unknown. This study evaluated 4-year outcomes following rATG bridge with delayed CNI for renal sparing post-LT.

*Methods: This retrospective, single center, cohort study (7/2014-5/2018) evaluated patients (pts) with serum creatinine (SCr) >2 mg/dL prior to LT (PRE group) or who required CRRT/had a SCr >2 mg/dL within 48 hours of LT (POST group) that received rATG 1.5mg/kg/dose according to CD3 suppression (<25 cells /uL) for 7 days with delayed TAC initiation. TAC trough targets until day 90 were 6-8 ng/mL, then 3-6 ng/mL. Prior LT, multiorgan transplant, graft loss by 1 year (yr), or enrollment in another study were excluded. Estimated glomerular filtration rates (eGFR) and chronic kidney disease (CKD) category was measured on post-operative day 1, 2, 7, 14, twice monthly to month 12, and twice yearly to yr 4. Due to improved accuracy before and after LT, eGFR was assessed via the Glomerular Filtration Rate Assessment in Liver Disease Model (GRAIL) calculation. Other outcomes include: rATG bridge protocol adherence, patient/graft survival, biopsy-proven acute rejection (BPAR), infection (received treatment for cytomegalovirus, bacterial or fungal infection), and malignancy (any diagnosis of cancer post-LT).

*Results: 65 LT pts (27 PRE and 38 POST) were included; 106 excluded. Demographics were similar between PRE and POST groups with the exception of MELD at match (median of 35 PRE and 22 in POST groups). Outcomes summarized in Table 1. At 4 yrs post-LT, mean eGFR was 66 and 68 mL/min/1.73m² for the PRE and POST respectively. CKD remained stable over time with majority in stage 2 (Figures 1 and 2). rATG was administered per protocol in 94%; rATG dosing was altered in 4 pts due to tolerability. 6 episodes of BPAR occurred in 5 pts (median 323 days post-LT); treated successfully with steroids and/or increased immunosuppression. Infection occurred in 45% within 1 yr (median 46 days post-LT). Malignancy occurred in 5 pts within 4 yrs (median 2.2 yrs post-LT). 3 died after 1 yr (median 3.2 yrs post-LT).

*Conclusions: Our data demonstrates that rATG is safe and effective post-LT to delay TAC. Renal function calculated via GRAIL not only recovered rapidly post-LT but did not decline and remained excellent at CKD stage 2 over the 4 yr study period. Next steps will be to compare these findings to the cohort of LT pts without renal dysfunction that did not receive rATG bridge protocol.

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