Antithymocyte globulin treatment in patients with aplastic anemia: a prospective randomized trial.

We evaluated the efficacy of antithymocyte globulin for the treatment of moderate to severe aplastic anemia in a randomized controlled study. Eleven of 21 patients initially randomized to receive antithymocyte globulin (given intravenously on eight consecutive days) had sustained improvement in hematopoiesis within three months of treatment; none of 21 control patients who received supportive care alone improved (P = 0.0005). Six of 12 control patients who subsequently received antithymocyte globulin improved. Responders had gradual improvement in hematopoiesis, but none recovered completely normal peripheral-blood counts. The severity of bone-marrow failure, age, cause of aplastic anemia, and transfusion history had no apparent bearing on treatment outcome. The interval from diagnosis to antithymocyte globulin treatment correlated inversely with the chance of a treatment response, although this correlation was not statistically significant. These data indicate that antithymocyte globulin is effective in improving hematopoiesis in some patients with aplastic anemia.