High-dose Alemtuzumab-Cyclosporine vs Tacrolimus-Methotrexate-Sirolimus for Chronic Graft-versus-Host Disease Prevention

• High-dose alemtuzumab led to effective suppression of chronic GVHD.

• Lymphodepletion delays Tn recovery resulting in lower TCR repertoire and higher Treg:Tn.

Chronic graft-versus-host disease (cGVHD) remains a significant problem for patients after allogeneic hematopoietic stem cell transplants (allo-HSCT). While in vivo lymphodepletion by antibodies for cGVHD prophylaxis has been explored in the myeloablative setting, its effects after reduced intensity conditioning (RIC) are not well described. Patients (n=83) with hematologic malignancies underwent targeted lymphodepletion chemotherapy followed by a RIC allo-HSCT using peripheral blood stem cells from unrelated donors. Patients were randomized to two GVHD prophylaxis arms: high-dose alemtuzumab/cyclosporine (AC, n=44) and tacrolimus/methotrexate/sirolimus (TMS, n=39) with the primary endpoint of cumulative incidence of severe cGVHD. The incidence of severe cGVHD was lower with AC vs TMS prophylaxis at 1- and 5-years (0% vs 10.3% and 4.5% vs 28.5%, overall p=0.0002), as well as any grade (p=0.003) and moderate-severe (p<0.0001) cGVHD. AC was associated with higher rates of grade III-IV infections (p=0.02) and relapse (52% vs 21%, p=0.003) with a shorter 5-year PFS (18% vs 41%, p=0.01) and no difference in 5-year GRFS, OS, or NRM. AC severely depleted naïve T-cells reconstitution, resulting in reduced TCR repertoire diversity, smaller populations of CD4 Treg and CD8 Tscm, but a higher ratio of Treg to naïve T-cells at 6 months. In summary, an alemtuzumab-based regimen successfully reduced the rate and severity of cGVHD after RIC allo-HSCT and resulted in a distinct immunomodulatory profile which may have reduced cGVHD incidence and severity. However, increased infections and relapse resulted in a lack of survival benefit after long-term follow-up. ClinicalTrials.gov identifier: NCT00520130