Background In recent years, growing evidence has demonstrated the potential of anti-thymocyte globulin (ATG) combined with post-transplant cyclophosphamide (PTCY) as an effective strategy for graft-versus-host disease (GVHD) prophylaxis. This regimen appears to significantly reduce the incidence of both acute and chronic GVHD. However, the optimal dosing of ATG in combination with PTCY requires further investigation through well-designed clinical trials.

Methods Clinical data from 29 patients who underwent allo-HSCT at Yantai Yuhuangding Hospital between June 2022 and May 2025 were retrospectively analyzed (AML: 14 cases, MDS: 8 cases, ALL: 5 cases, MPAL: 2 cases; Haploidentical transplantation: 24 cases, Unrelated donor transplantation: 5 cases). The GVHD prophylaxis regimen consisted of low-dose ATG (2.5 mg/kg on days -2 and -1), fractionated low-dose PTCY (25 mg/kg on days +3 and +4), cyclosporine (2.5 mg/kg /day starting from day +5), and mycophenolate mofetil (0.5 g twice daily from day +5).

Results The median age of the 29 patients was 48.5 years (range: 16–65), with 16 males and 13 females. The median follow-up was 349 days. The median time to neutrophil engraftment was 12 days (range: 9–21), and the median time to platelet engraftment was 13 days (range: 9–38). One patient experienced primary graft failure (graft rejection) and underwent a second transplantation with a different donor on day +37, achieving successful engraftment. At D+100, the cumulative incidence of grade I–IV acute GVHD (aGVHD) was 8.4%, the incidence of grade III–IV aGVHD was 3.8%, with only one case of grade IV intestinal aGVHD. The 1-year Chronic GVHD (cGVHD) incidence: 17.4% (moderate-to-severe cGVHD: 5.9%). At D+100, non-relapse mortality (NRM): 7%, EBV reactivation: 48.3% (plasma EBV DNA >1000 copies/mL :7.4%; EBV-PTLD: one case), CMV reactivation: 51.7% (CMV DNA >1000 copies/mL :27.6%). D+30, The incidence of bloodstream infection (BSI) was 13.8%. The incidence of grade I–II hemorrhagic cystitis was 10.3%, with no grade III–IV cases. Grade I–II oral mucositis was observed in 31%, with no severe cases. No significant cardiac adverse events or grade ≥2 fluid overload (FO) were reported. The 1-year relapse rate was 17.2%. The 1-year overall survival (OS) and progression-free survival (PFS) rates were 77.3% and 62.5%. Among the 24 non-ALL patients, the 1-year OS and PFS were 80.9% and 70.3%. By the end of follow-up, six patients had died due to relapse (n=2), shock (n=1), cGVHD (n=1), TMA (n=1), and secondary graft failure (n=1).

Conclusion GVHD prophylaxis with low-dose ATG combined with fractionated low-dose PTCY in allogeneic hematopoietic stem cell transplantation demonstrated excellent tolerability, with a remarkably low incidence of grade III-IV GVHD and absence of cardiac adverse events. However, due to the small sample size and short follow-up, further prospective, large-scale, multicenter randomized controlled trials are needed to validate the superiority of this regimen.

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2025
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