Calcineurin Inhibitor–Free Graft-versus-Host Disease Prophylaxis with Post-Transplantation Cyclophosphamide and Brief-Course Sirolimus Following Reduced-Intensity Peripheral Blood Stem Cell Transplantation

• Calcineurin inhibitor (CNI)-free GVHD prophylaxis with post-transplant cyclophosphamide (Cy) and brief course sirolimus appears to be a safe and effective alternative to standard CNI-based immunosuppression following reduced-intensity allogeneic peripheral blood stem cell transplantation.
• Potential benefits include reduced renal toxicity, improved immune reconstitution manifested by low risk of infectious complications, modest rates of GVHD, and more rapid discontinuation of immunosuppressive therapy.

Calcineurin inhibitors (CNIs) form the foundation of current graft-versus-host disease (GVHD) prophylaxis regimens. We hypothesized that a CNI-free regimen consisting of post-transplantation cyclophosphamide (PTCy) and brief-course sirolimus would reduce chronic GVHD and nonrelapse mortality (NRM) after reduced-intensity conditioning allogeneic peripheral blood stem cell transplantation (PBSCT). Twenty-six patients (median age, 61 years) underwent unmanipulated PBSCT from an 8/8 locus-matched donor (matched related donor, n = 17; natched unrelated donor, n = 9). GVHD prophylaxis consisted of PTCy and brief-course sirolimus. Donor engraftment occurred in all patients. The cumulative incidence (CI) of grade II-IV acute GVHD, grade III-IV acute GVHD, and chronic GVHD was 46%, 15%, and 31% respectively. One-year NRM was 4%. The median time to immunosuppression discontinuation was day +138. With a median follow-up of 20 months, the estimated 2-year overall survival was 71%, estimated disease-free survival was 64%, and estimated relapse incidence was 32%. In patients with a lymphoid malignancy (eg, chronic lymphoblastic leukemia, non-Hodgkin lymphoma, Hodgkin disease), 2-year disease-free survival was 100%, and there were no relapses. Good immune reconstitution was evidenced by low cytomegalovirus reactivation rate of 21% (4 of 19 at-risk patients). GVHD prophylaxis with PTCy and sirolimus achieves consistent donor engraftment, low rates of chronic GVHD and NRM, and excellent outcomes in recipients of HLA-identical related and unrelated donor allogeneic PBSCT.