#5504 EXTENDED VALIDATION OF THE IBOX IN REAL LIFE SETTING, DIFFERENT TRANSPLANT SYSTEMS AND CLINICAL TRIALS: THE IBOX EXTENDED TRIAL

Abstract

Abstract Background and Aims The iBox is a validated prognostication system predicting long-term kidney allograft failure. Recently, it received regulatory endorsement by EMA, for surrogate endpoint for clinical trials. As the iBox system was primarily built using a deep phenotyped cohort, there is a need for proof of validity in extended clinical scenarios, geographic distinct medico-economic cohorts and transplant allocation systems. Method 10,851 transplant recipients were included from 17 academic medical centers from France, Belgium, Spain, Germany, Finland, United States, Brazil and Argentina. We applied to these cohorts the iBox algorithm that integrates eight independent prognostic factors including the time from transplantation to risk evaluation, functional parameters (eGFR, proteinuria), allograft histological lesions (IFTA, g+ptc, i+t, cg Banff scores), and circulating anti-HLA DSA. We stratified the performances of the iBox according to several real-life scenarios, including: 1) iBox + different eGFR formulas (MDRD186, MDRD175, CKD-Epi); 2) iBox + urinary dipstick; 3) iBox Functional + Structural (absence of DSA measurements); 4) iBox functional + Immunological (absence of histology); 5) iBox in response to treatment in T-cell mediated rejection (TCMR); 6) iBox for in response to treatment antibody mediated rejection (ABMR) clinical trials. The performances of the iBox system were assessed with the discrimination (C-index) and calibration. Results The derivation cohort included 4,000 recipients from France, and the international external validation cohort included 6,851 recipients from Europe (France, Belgium, Spain, Germany, Finland n = 4,643), the United States (n = 1,537) and South America (Brazil, Argentina n = 671). The mean recipient age was 50.26 years (14.05) with a median follow-up after evaluations of 5.41 years [IQR: 3.26 to 7]. 1336 patients (12.31%) lost their graft during the study follow-up. The performances of the iBox were confirmed in the different real-life setting with the following C-Index: 1) iBox + different eGFR formulas (MDRD186, MDRD175, CKD-Epi) 0.81; 2) iBox + urinary dipstick 0.80; 3) iBox Functional + Structural (histology) 0.80 (derivation) and 0.84 (validation); 4) iBox functional + Immunological 0.80 (derivation) and 0.83 (validation); 5) iBox in response to treatment in T-cell mediated rejection 0.81; 6) iBox for in response to treatment antibody mediated rejection trials 0.81. The score showed an accurate calibration in every scenario. Conclusion The iBoxEXTENDED trial confirms in various medico-economic settings the performances transportability and surrogacy of the iBox system, further reinforcing its use as a surrogate end point for clinical trials including TCMR and ABMR.