Horse ATG Superior to Rabbit ATG for Severe Aplastic Anemia

Higher hematological response, survival rate with horse antithymocyte globulin and cyclosporine

WEDNESDAY, Aug. 3 (HealthDay News) -- In patients with severe aplastic anemia, rabbit antithymocyte globulin (ATG) and cyclosporine is inferior to horse ATG and cyclosporine as a first-line treatment, according to a study published in the Aug. 4 issue of the New England Journal of Medicine.

Phillip Scheinberg, M.D., from the National Heart, Lung, and Blood Institute in Bethesda, Md., and colleagues compared the efficacy of horse ATG with rabbit ATG in patients with severe aplastic anemia who had not received previous treatment. The study was designed to enroll 120 patient to be randomly allocated to either rabbit ATG and cyclosporine (60 patients), or horse ATG and cyclosporine (60 patients), between 2005 and 2010. The study design had the capacity to detect a difference of 25 percentage points in the response rate. The main outcome of the study was hematological response determined by blood counts at six months.

The investigators found that, at six months, the horse ATG showed an unexpectedly greater rate of hematologic response than rabbit ATG (68 versus 37 percent). The horse ATG group showed a significantly higher overall survival rate at three years than the rabbit ATG group, when the data were censored during stem-cell transplantation (96 versus 76 percent) and at the time of uncensored stem-cell transplantation (94 versus 70 percent).

"In a randomized study, rabbit ATG was inferior to horse ATG as a first treatment for severe aplastic anemia, as indicated by hematologic response and survival," the authors write.

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