Can only partial T-cell depletion of the graft before hematopoietic stem cell transplantation mitigate graft-versus-host disease while preserving a graft-versus-leukemia reaction? A prospective phase II study.

The study comprised 37 consecutive patients who underwent transplantation with a Campath-1H in vitro T cell–depleted granulocyte colony-stimulating factor–mobilized peripheral blood stem cell graft from an HLA-identical sibling, followed 24 hours later by an unmanipulated graft. Acute graft-versus-host disease (GVHD) was limited to grade I to II, whereas chronic graft-versus-host disease occurred in 9 patients, mostly (n = 7) with limited disease. Molecular relapses (8 chronic myeloid leukemia [CML] and 1 non-Hodgkin lymphoma) that occurred not earlier than the sixth month after transplantation were treated with donor lymphocyte infusion (DLI), which induced complete remission in all but 1 CML patient with persistent very low BCR-ABL molecular levels. With a median follow-up of 54 months (range, 29-84 months), the actuarial 5-year overall survival, disease-free survival, and transplant-related mortality are 78% (95% confidence interval [CI], 52%-88%), 78% (95% CI, 52%-86%), and 6% (95% CI, 1.5%-32%), respectively. All CML patients are alive and free of disease. The results of this prospective, nonrandomized study show that incomplete T-cell depletion in vitro with Campath-1H (in combination with DLI for molecular relapses in CML) may decrease the incidence of GVHD and transplant-related mortality with no adverse effect on disease-free survival. The described method decreases the number of T cells to an extent that severe GVHD is prevented while relapse is postponed to a time when the patient can be treated with DLI without severe side effects.