*Purpose: Though tacrolimus (TAC) is a cornerstone of maintenance immunosuppression in kidney transplant recipients, some patients have significant side effects related to TAC. Conversion from TAC to belatacept (BELA, a co-stimulation blockade) may be associated with a high incidence of acute rejection (AR) in the first few months of conversion. We report successful conversion of 7 adolescents and young adults from TAC to BELA using a modified protocol since there is a very limited data in this age group.

*Methods: Seven adolescents and young adults were converted from TAC to BELA. Indication for conversion was high creatinine in 3, TAC intolerance in 2, non-adherence and development of de-novo insulin dependent diabetes mellitus (IDDM) in 1 each. These patients received IV BELA (5mg/kg on day 1, 15, 30 and 60) and then monthly thereafter. TAC dose was reduced by 50% on day 30, tapered between day 30-60 and discontinued at day 60. Renal function, CMV, EBV and BKV PCR were monitored at the time of each infusion for the first 6 months. Donor specific antibodies (DSA) were monitored at 3 and 6 months and annually thereafter. Other maintenance immunosuppressive medications (mycophenolate mofetil in 5/7 and sirolimus in 2/7 and low dose prednisone in all except in a patient with IDDM) were continued.

*Results: These patients were between 16.6-20.7 (mean 18.2) years of age at the time of conversion. There were 4 living related and 3 deceased donor transplant recipients. All were EBV seropositive at transplant. Of the 7 patients, 5 were <6 months and 2 were 3 years post-transplant at conversion. Estimated GFR at conversion was 75.5 +16.6 ml min/1.73m² and was 75.1 +18.1ml/min/1.73m² after a mean follow up of 15 (4-40) months. One CMV mismatched patient developed asymptomatic CMV viremia 2 months after conversion and responded to oral valganciclovir. Two patients had transient low grade EBV replication. No patient had AR, hospitalization or development of de novo DSA during the follow up period. Patient with IDDM had 25% reduction in insulin dose and improvement in hemoglobin A1C from 8.5 to 6.6 after 5 months of conversion and 3 months of stopping tacrolimus.

*Conclusions: Conversion from TAC to BELA is safe and effective in adolescents and young adults without AR and infections. Since non-adherence and poor long-term graft survival is very prevalent in this age group, IV infusion of BELA as a long-term maintenance immunosuppression may be particularly useful in this population and needs to be studied.

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