Clinical impact of human Jurkat T-cell-line-derived antithymocyte globulin in multiple myeloma patients undergoing allogeneic stem cell transplantation

Background: Antithymocyte globulin or human Jurkat T-cell-line-derived antilymphocyte globulin is used in allogeneic stem cell transplantation to induce in vivo T-cell depletion to facilitate engraftment and lower graft-versus-host disease. In vitro studies suggest that antithymocyte globulin, besides causing T-cell depletion, has strong anti-myeloma activity. Design and Methods: We evaluated the anti-myeloma activity of antilymphocyte globulin in a melphalan/fludarabinebased reduced intensity conditioning regimen as well as the incidence of graft-versus-host disease in 138 multiple myeloma patients who underwent allogeneic stem cell transplantation with (n=79) or without (n=59) antilymphocyte globulin. Results: Leukocyte and platelet engraftment were faster in the group not receiving antilymphocyte globulin (13 vs. 16 days, p<0.001 and 11 vs. 19 days, p< 0.001, respectively). Inclusion of antithymocyte globulin led to a better day 100 overall response rate (93% vs. 78%, p=0.03) and complete response rate (59% vs. 39%, p=0.04), to a lower incidence of both acute grade III/IV graft-versus-host-disease (11% vs. 22%, p=0.10) and chronic graft-versus-host disease (23% vs. 65%, p<0.001) and to a trend to improved event-free survival at 3 years (39% vs. 27%, p=0.5). There was no difference in the estimated cumulative incidence of treatment-related mortality at 1 year between the groups receiving or not antilymphocyte globulin (25% vs. 26%). In a multivariate analysis treatment with antilymphocyte globulin was the only significant factor for achievement of a complete remission (RR:2.57, p=0.02). Conclusions: Inclusion of antithymocyte globulin in allogeneic stem cell transplantation protocols for patients with multiple myeloma may increase remission rates and at the same time prevent graft-versus-host disease with no increase of relapses.