Use of an anti-interleukin-2 receptor monoclonal antibody for GVHD prophylaxis in unrelated donor BMT.

Severe acute GVHD remains the main complication in unrelated donor BMT (UD-BMT). The previous encouraging reports on the use of anti-IL-2 receptor monoclonal Ab (33B31) for GVHD prophylaxis in genoidentical BMT led us to add this Ab to the standard GVHD prophylaxis regimen (MTX plus CsA). Sixty-four consecutive patients received 33B31, 20 mg on days 1 and 2, then 10 mg per day from day 3 to day 28 in association with CsA and MTX. They were compared with a historical control group of 89 patients who received conventional GVHD prophylaxis. The 33B31 was well tolerated. We did not find any statistical difference in terms of incidence and time of onset of severe GVHD, occurrence of chronic GVHD, engraftment, relapse or survival among the two groups. Immunization occurred but did not influence serum levels of 33B31. No correlation was found between the severity of GVHD and serum Ab levels. We conclude that other approaches for reducing acute GVHD should be developed to improve UD-BMT results.