#6147 BELATACEPT OUTCOMES IN PEDIATRIC KIDNEY TRANSPLANTATION: AN INTERNATIONAL MULTICENTER STUDY

Abstract

Abstract Background and Aims Belatacept is a co-stimulation blocker associated with better long-term outcomes in adult patients compared to CNI based regimens. Data on its use in older children and young adults are lacking. We are the 1st to report outcomes for 45 pediatric kidney transplant recipients converted to belatacept. Method 45 patients were included from 4 centers (USA and France) between 05/2018 and 12/2021. Patients received an induction with basiliximab (n = 39) or ATG (n = 6). Maintenance immunosuppression included CNI, MMF +/− steroids. Patients’ viral status (EBV, CMV) were monitored monthly and allograft biopsies were performed prior and ∼6 months after starting belatacept. The first 5 belatacept injections were administered at 5 mg/kg/dose (10 mg/kg/dose if early conversion) every 2 weeks, then monthly. CNI were progressively reduced and stopped. MMF doses were also increased at CNI withdrawal. Results Median age at conversion was 17.7 y (range 10.3-20.6). 7/45 patients received an early conversion (median: 1 month post-transplant, IQR 0.5-1.2): 6 patients because of delayed graft function and 1 to avoid CNI toxicity (post-transplant diabetes). 38/45 patients were converted after a median of 4.1 years post-transplant (IQR 1.7-6.0). Conversion indication was based on the need for long term CNI avoidance: either because of toxicity (histology, post-transplant diabetes, tremors; n = 13) or sub-optimal creatinine (n = 12) or to improve adherence (e.g. monthly IV-treatment, n = 13). CNI were withdrawn in 42/45 patients by a median of 2.4 months (IQR 1.4-6.0). GFR was stable or improved over a median follow-up time of 1.6 years (IQR 1.1-2.4), Fig 1 A. Rejection episodes were observed in 10/45 patients (22%) after a median of 10.2 months (IQR 6.1-15.8) and included 7 TCMR, 2 ABMR and 1 mixed rejection. None of these patients were converted early (<3 m), 5 had been converted for non-adherence, 4 had pre-existing DSA and 4 had prior history of rejection. Evolution of GFR in rejectors is shown in Fig 1 B. CNI were reintroduced for 6/10 and belatacept stopped for 3/10. Regarding viral complications, 1 severe BKv nephropathy required the discontinuation of belatacept. All patients were EBV+ at conversion (4 were EBV- at the time of transplant). No EBV replication was observed. Conclusion Selected pediatric kidney recipients benefit from long-term CNI toxicity avoidance, but selection criteria need to be refined to avoid rejection under costimulation blockade.