Introduction: Calcineurin inhibitor (CNI) toxicity and nonadherence with allograft rejection are significant causes of kidney allograft loss in pediatric kidney transplant recipients. Belatacept is a novel immunosuppressive agent with a reduced side effect profile administered monthly via infusion. The purpose of this study is to assess outcomes of pediatric kidney transplant recipients who were converted from a CNI-based immunosuppression regimen to a belatacept-based regimen.
Methods: We identified all pediatric kidney transplant recipients at our academic institution who were converted to a belatacept-based regimen from November 2015 to November 2021. Recipient and donor demographic data, indication for conversion, patient and allograft survival, and alloimmune events were evaluated.
Results: 18 pediatric kidney transplant recipients were converted to a belatacept-based immunosuppression regimen. Median recipient age at time of transplant was 12 years. 8 allografts were from deceased donors and 10 were from living donors. The primary indication for conversion was rejection and/or noncompliance, which accounted for 12 recipients. The other 6 recipients were converted to belatacept for CNI toxicity (n=3), worsening renal function (n=2), and mycophenolate mofetil toxicity (n=1). Median time from transplant to conversion was 37 months. 94% of patients (17/18) were fully compliant with monthly belatacept infusions. 
Patient survival was 100% and allograft survival was 89% (16/18). Glomerular filtration rate (GFR) was preserved in 72% of patients (13/18) with a median GFR of 42.5 mL/min one year after conversion. Fewer patients experienced biopsy-proven acute rejection after conversion to belatacept. Of the 18 patients, 10 had no donor specific antibodies (DSA) prior to conversion. Of those, 9 remained DSA negative, and one patient developed DSA following conversion. Of the 8 patients with DSA prior to conversion, one became DSA negative. Of the patients converted to belatacept for biopsy-proven CNI toxicity, all had improvement in renal function (median GFR 40 to 65mL/min over the first year) and none experienced rejection. 3 patients were transitioned back to CNI-based immunosuppression for rejection (n=1), transportation issues (n=1), and COVID-19 infection (n=1).
Conclusion: This is the largest known series of pediatric kidney transplant recipients undergoing conversion to belatacept-based immunosuppression. Compliance with belatacept appears to be high and gives an effective option for pediatric recipients who face higher rates of nonadherence. Further work is needed to validate this data prospectively in large scale randomized controlled trials with long term follow up.