Reduced-Dose PTCy Plus Post-Engraftment Low-Dose ATG for GVHD Prophylaxis in Haploidentical PBSC Transplantation

Area of Science:

• Hematopoietic Stem Cell Transplantation
• Immunosuppression Strategies
• Graft-versus-Host Disease Prevention

Background:

• Post-transplant cyclophosphamide (PTCy) and antithymocyte globulin (ATG) are common for GVHD prophylaxis in haploidentical HCT.
• Optimal PTCy and ATG dosing and timing require further investigation to balance efficacy and toxicity.
• This study evaluated a modified regimen of reduced-dose PTCy and delayed low-dose ATG.

Purpose of the Study:

• To assess the efficacy and safety of a modified GVHD prophylaxis regimen.
• To compare reduced-dose PTCy with delayed ATG against conventional ATG-based prophylaxis.
• To evaluate rates of acute GVHD, transplant-related toxicities, and survival outcomes.

Main Methods:

• Retrospective analysis of 99 patients undergoing myeloablative haploidentical HCT.
• Comparison between a modified PTCy-ATG group (n=30) and a conventional ATG group (n=69).
• Primary endpoint: cumulative incidence of grade II-IV acute GVHD.

Main Results:

• The PTCy-ATG group showed a significantly lower incidence of grade II-IV acute GVHD (13.8% vs. 36.7%).
• Reduced rates of hemorrhagic cystitis and bloodstream infections were observed in the PTCy-ATG group.
• No significant differences in grade III-IV acute GVHD, chronic GVHD, mortality, relapse, or survival were found between groups.

Conclusions:

• Reduced-dose PTCy with delayed low-dose ATG effectively reduces acute GVHD and certain toxicities post-haploidentical HCT.
• The modified regimen appears safe regarding relapse and survival outcomes.
• Prospective studies are warranted to confirm these findings with contemporary regimens.