Antibody mediated rejection (ABMR) is a major cause of graft loss after kidney transplantation (KT) and is mainly associated with preformed anti-HLA donor specific antibodies (DSAs) (phenotype 1) or de novo DSAs (dnDSAs) (phenotype 2). Preexisting DSA-associated ABMR have superior graft survival compared with dnDSA-associated ABMR, which could partly be explained by the fact that patients with de novo DSA-associated ABMR have biopsy later, when graft dysfunction and/or proteinuria are already present. ABMR is a progressive process with an early stage called subclinical ABMR (sABMR), in which histological lesions are present in the kidney graft without clinical graft dysfunction. These early lesions are now well recognized as risk factors for transplant glomerulopathy and poor graft survival in phenotype 1 ABMR (ref 5). The impact of sABMR associated with dnDSA at any time post-transplant has been less studied and reported. Recently, a retrospective multicenter study was published, within the Spiesser Group that included 123 patients without graft dysfunction who underwent graft biopsy because of the presence of dnDSA (One Lambda, MFI \> 1000). Performing a kidney graft biopsy after dnDSA indentification without renal dysfunction leads to the diagnosis of active sABMR in 35 % of cases. Nevertheless, no effect of standard of care treatment in active sABMR was observed. Very recently, an expert consensus for the recommended treatment for ABMR after KT was published. It was conclude that the clear lack of evidence but a standard of care for ABMR was nevertheless defined. Therefore, the current proposal is to evaluate a new strategy for active sABMR, testing a conversion from calcineurin inhibitor (CNI) to belatacept associated with the recently recommended standard of care (SOC) compared to continuing CNI. Belatacept might help to manage nonadherence, decrease the toxicity of CNI on an endothelium already affected by microvascular inflammation, and reduce DSA titers.
The monitoring of dnDSA after KT and an indication graft biopsy in case of appearance, even in the absence of graft dysfunction, is not part of a routine clinical practice in all KT centers. This strategy could be a valuable option, in order to begin treatment of ABMR before graft dysfunction occurs, and therefore to improve prognosis associated with phenotype 2 ABMR. Parajuli et al.4 suggested that early diagnosis and treatment of sABMR with SOC, using DSA monitoring may improve outcomes after KT, but this is a retrospective and no-randomized study. This study will be the first prospective randomized study in the context of de novo DSA. The objective is to evaluate a new combination of treatment for ABMR in the context of dnDSA with subclinical lesions and in the same time may help to determine the real incidence of sABMR in KT recipients with subclinical dnDSA. The use of belatacept in the context of sABMR to improve the non-adherence and to decrease the endothelial toxicity had never been evaluated in a prospective way.
Kidney transplant recipient
Adult
De novo DSA (MFI > 1000 using the Luminex single antigen beads assay or positive with the manufacturer criteria according to the Luminex assay) absent on the day of kidney transplantation and in the sera prior to kidney transplantation
No clinical graft dysfunction at time of DSA detection (< 20 % variation of eGFR compared to last 3 months before detection and < 0,5 g/g proteinuria/creatinuria ratio)
Minor
Specific treatment for DSA occurrence before kidney graft biopsy: IVIG or rituximab or plasmapheresis or immunoabsorption
ABO incompatible kidney transplantation
Combined transplantation
Parallel
Conversion to Belatacep
DrugCNI will be tapered within 3 months: 75 % of initial dose on the first month, 50 % on the second month, 25 % on the third month, and stopped and a conversion to Belatacept will be performed. It will be administered (6mg/kg) every 2W for the first 2 months and then every month until kidney graft survival.
Standard of care treatment (SOC regimen) with Tacrolimus
DrugTacrolimus will be continued until kidney graft survival with objective of whole blood through levels between 6 and 8 ng/mL
The efficacy of belatacept combined with standard of care, compared to calcineurin inhibitors (CNI) combined with standard of care, among kidney transplant recipients with sABMR
Proportion in each arm, at 12 months post randomization, of patients with: * decrease eGFR \> 20% at 12 months post randomization, according to CKD-EPI formula * or bad features on 12-month protocol biopsy: cg \> 1 * or chronic active ABMR according Banff 2019 classification, * or \< 50 % MFI reduction of DSA, * or proteinuria/creatinuria ratio \> 0.5 g/g, * or death, * or graft loss.
Presence of chronic active ABMR
Presence of ABMR defined according to the Banff 2019 classification, assessed on the kidney graft biopsy
Serum creatinine and calculation of eGFR
Assessment of renal function based on serum creatinine levels and estimated glomerular filtration rate (eGFR), calculated using the CKD-EPI formula
Proteinuria/creatininuria ratio
Evaluation of proteinuria using the proteinuria-to-creatininuria ratio measured on urine samples
Significant Proteinuria
Proportion of patients presenting significant proteinuria, defined as a proteinuria-to-creatininuria ratio \> 0.5
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