*Purpose: Monoclonal antibody therapy causes profound and sustained lymphocyte depletion thus increasing the risk of viral infections. While studies exist evaluating the outcomes of alemtuzumab and rabbit anti-thymocyte globulin (rATG), there is limited data evaluating the differences in the rate of viral infections between these two agents. The goal of this study was to evaluate the incidence of viral infections between patients receiving alemtuzumab and rATG for induction immunosuppression.

*Methods: This was a retrospective, single center study of adult kidney transplant recipients (KTRs) who received either rATG from 11/2011 to 12/2015 or alemtuzumab from 1/2015 to 7/2017 for induction immunosuppression. The primary outcome was the incidence of the composite endpoint between the two cohorts. The composite endpoint included cytomegalovirus (CMV) viremia, BK viremia, BK nephropathy and adenovirus viremia.

*Results: Of the 624 KTRs included, 400 (64.1%) received alemtuzumab and 224 (35.9%) received rATG. The rATG cohort contained a significantly higher proportion of sensitized patients, recipients of living donor allografts, and more likely to be on prednisone at discharge (Table 1). The alemtuzumab cohort had a significantly higher incidence of the composite endpoint compared to rATG (31% vs 21.4%, p=0.01). The composite endpoint was primarily driven by the incidence of CMV viremia (20.8% vs. 13.8%, p=0.03). The difference was largely seen during the first 120 days post-transplant (8% vs 1.7%, p<0.001), which may be related to the profound leukopenia seen in patients who received alemtuzumab (Figure 1). Further analysis found CMV moderate risk KTRs who received alemtuzumab had a 2-fold increased risk of developing CMV viremia compared to rATG (23.2% vs 10.5%, p=0.001).

*Conclusions: Viral infections, specifically CMV viremia, occurred at significantly higher rates in the setting of alemtuzumab induction, compared to rATG.

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