Long-Term Outcomes of ATG With or Without PTCy for GVHD Prophylaxis

By Patrick Daly - Last Updated: October 3, 2022

A recent study reported that a modified anti-thymocyte globulin and post-transplant cyclophosphamide (ATG/PTCy) regimen appeared to reduce the risk of acute and chronic graft-versus-host disease (GVHD) compared with standard ATG protocol. However, the authors found no differences in long-term outcomes between the 2 strategies.

The study, published in Frontiers in Immunology, retrospectively enrolled 118 patients up to 60 years of age with acute leukemia from the authors’ center. All patients received the same myeloablative conditioning regimen prior to haploidentical peripheral blood stem cell transplantation (haplo-PBSCT).

Seventy-eight patients received the modified combination of ATG 2.5 mg/kg/day on the 3 days prior to transplant and PTCy 40 mg/kg/day on day 3 and 4 after transplant. The remaining 40 patients received standard ATG 2.5 mg/kg/day on the 4 days prior to transplant.

Modified Anti-Thymocyte Globulin and Post-Transplant Cyclophosphamide Regimen

Over a median follow-up time of 5.36 years, the authors observed cumulative incidences of neutrophil and platelet engraftment and cytomegalovirus (CMV) reactivation were comparable between the groups. The rates of 5-year overall, disease-free, and GVHD-free relapse-free survival were also similar at 53.34%, 49.77%, and 36.04%, respectively, for ATG/PTCy compared to 47.5%, 42.5%, and 22.5%, respectively, for ATG.

Notably, compared with the ATG group, the ATG/PTCy group had noticeably lower cumulative incidences of grade II-IV acute GVHD (aGVHD), grade III-IV aGVHD, and chronic GVHD at 34.6% versus 57.5%; 8.97% versus 30%; and 13.63% versus 38.23%, respectively. However, the authors noted that the modified ATG/PTCy regimen was also associated with an increased risk of relapse (hazard ratio, 2.23; P=.039).

Overall, the researchers showed that a modified ATG/PTCy regimen has the potential to improve GVHD prophylaxis versus a standard ATG regimen—though long-term outcomes in the study’s retrospective cohorts were not statistically different. Despite that finding, the authors suggested that “certain adjustments in the immunosuppression protocol are warranted to improve the outcome.”

Related: Individualized Anti-Thymocyte Globulin for GVHD Prevention in Pediatric HSCT