*Purpose: The purpose of the study was to examine preliminary efficacy and tolerability of bortezomib, a protease inhibitor, in treatment-refractory antibody mediated rejection (AMR) in pediatric kidney transplant patients.

*Methods: Patients who received bortezomib (4 doses at 1.3 mg/m² per cycle) for AMR (per Banff 2017 criteria) at a large children’s hospital over a 1.5 year period were included. Charts were abstracted for demographic and clinical data. Primary outcomes were change in donor specific antibodies (DSA) and estimated glomerular filtration rate (eGFR; based on bedside Schwartz formula) before, and 1 and 3 months after bortezomib. Descriptive statistics were performed.

*Results: Six patients were included (baseline characteristics and outcomes summarized in Table 1). Two cycles of bortezomib were given as a 2^nd line agent after increased baseline immunosuppression and other treatments (e.g., IVIG, rituximab, plasmapheresis, and/or thymoglobulin) failed to resolve DSA or improve renal function. Two patients had DSA resolution (30%) and 2 different patients showed improvement in eGFR (30%). Data collection is still ongoing for the remaining patients. No serious adverse effects were noted.

*Conclusions: In this small, single-center study of bortezomib for refractory AMR in pediatric kidney transplant patients, we observed variable improvement in DSA and renal function. Bortezomib was well-tolerated, however efficacy evaluation was limited due to small sample size, lack of randomization, and short follow-up period. This study adds to the nascent but growing literature examining bortezomib for AMR in kidney transplanted youth.

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