#3052 mTOR inhibitors in kidney transplant recipients with high immunological risk: practical insights from clinical experience

The use of mTOR inhibitors (mTORi) is not usually considered in high immunological risk kidney transplant recipients (KTR) for a perceived increased risk of rejection. However, in most of the studies that examined the combination of mTORi with calcineurin inhibitors (CNI), hypersensitized patients have been excluded from enrollment. The aim of the present study is to analyze our clinical experience with the use of mTORi in association with calcineurin inhibitors (CNI) in this subset of patients.

Analysis of 212 consecutive kidney transplant recipients with a baseline calculated panel reactive antibody (cPRA) ≥50% who received a graft from June 2013 to December 2019. Immunosuppression was based on tacrolimus, steroids and, alternatively, mycophenolic acid (MPA; n = 96) or mTORi (either sirolimus or everolimus, target trough levels 3-8 ng/ml, n = 116) depending on the active Institution's protocol at the time of transplantation. The outcomes chosen included rejection-free, graft and patient survival and were analyzed by means of Cox-regression analysis.

Demographic and immunological characteristics were similar between groups, apart from the higher number of living donors in the MPA group (42.7% vs 14.7%%, P < 0.001). Baseline cPRA was 92.5 [76-98]% for the MPA and 94 [77.25-98]% for the mTORi group, respectively (P = 0.882). Induction therapy with lymphocyte-depleting agents was employed in the majority of patients (91.7% in the MPA group and 88.8% in the mTORi group, P = 0.898). Median follow-up time was 2.6 [1.45-4.05] years. Biopsy-proven rejection (either cellular or humoral) occurred in 33.3% of the MPA and in 19.8% of the mTORi group, respectively. Cox-regression analysis of rejection-free survival revealed better rejection-free survival with mTORi versus MPA (HR [95% CI], 0.54 [0.32-0.98], P = 0.028). The only other baseline factor associated with rejection was previous transplantation (HR [95% CI] 1.96 [1.07-3.60], P = 0.030). When entered into a bivariable Cox-regression analysis, both mTORi and previous transplantation maintained a statistical significant association with rejection (mTORi versus MPA HR [95% CI] 0.53 [0.31-0.91], P = 0.023, and previous transplantation HR [95% CI] 2.01 [1.09-3.69], P = 0.024). No differences between mTORi and MPA were noted for graft (HR [95% CI] 0.90 [0.40-2.02], P = 0.807) and patient survival (HR [95% CI] 1.23 [0.60-2.50, P = 0.606). Median creatinine 1 year after transplantation was 1.45 [1.11-1.98]mg/dl for the MPA group and 1.51 [1.09-2.06]mg/dl for the mTORi group (P = 0.917).

This retrospective study suggests that hypersensitized KTRs can receive safely a maintenance immunosuppression based on a combination of CNI with mTORi, without an increased risk of rejection.