*Purpose: Alemtuzumab is a lymphocyte-depleting monoclonal antibody used for renal transplant induction, and is associated with significant leukopenia, increased infections and malignancy. Multiple dosing strategies have been utilized, including weight-based regimens, however, the most common is a fixed-dose of 30mg. This study assesses safety outcomes of fixed-dose alemtuzumab when administered to recipients of lower weight when compared to their higher weight counterparts.

*Methods: This was a single-center, retrospective, cohort analysis in adult renal transplant recipients who received alemtuzumab for induction from Jan 2013-Oct 2018. Data was collected via chart review. Descriptive statistics were used for analysis. Patients received a single 30mg dose of alemtuzumab, followed by tacrolimus, MMF and early steroid withdrawal. Patients were divided into weight-based cohorts. The primary outcome was serious infections. Secondary outcomes included CMV infection, BK viremia, malignancy, graft loss, and death from transplant to present; rejection, graft function, WBC, filgrastim use, and hospital days were reported for the first year. Immunosuppression with tacrolimus and MMF was collected.

*Results: This study included 568 patients [48 (9%) <60 kg, 383 (67%) 60-100 kg, 137 (24%) >100 kg]. Baseline characteristics between the groups were similar, except the highest weight cohort had more men and DM, whereas the lowest weight cohort was more likely to have SLE. Despite the lowest weight cohort receiving 0.56 mg/kg of alemtuzumab compared to the 0.27 mg/kg administered to the highest weight cohort, there was no difference in safety outcomes. Conversely, the highest weight cohort did not have more rejection. The lowest weight cohort had a higher eGFR at 3 & 6 months post-transplant, which may be explained by a greater number of living donors (p=0.077), but this difference was not maintained at 1-yr.

*Conclusions: Fixed dose alemtuzumab was safe and effective across cohorts of varying weights. Despite variations in dosing practices, administration of a fixed-dose minimizes cost, reduces risk of dosing errors and allows for a simple single-dose induction regimen.

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