A randomized trial of antihuman thymocyte globulin versus murine monoclonal antihuman T-cell antibodies as immunosuppressive therapy for aplastic anemia.

A prospective randomized trial was undertaken to compare the efficacy and toxicity of murine antihunman T-cell monoclonal antibody (mcAb) therapy to that of horse antihuman thymocyte globulin (ATG) in the treatment of severe aplastic anemia (AA). Patients were randomized into one of the two treatment groups as well as to receive or not receive androgens. Median duration of aplasia prior to treatment was 1.5 and 2.2 months for the mcAb and ATG groups, respectively. One of 12 patients who received mcAb therapy had a partial response, whereas four of 13 patients receiving ATG had a complete or partial response. Of the 11 patients who failed mcAb treatment, six were subsequently treated with ATG and two improved. Ten of 13 patients who received ATG are surviving compared with seven of 12 patients who received mcAb. Toxicity of mcAb therapy was less than that of ATG. Future studies are needed to determine whether mcAbs known to be immunosuppressive are of benefit as therapy for patients with AA.