Editor’s Note: Hematopoietic stem cell transplantation (HSCT) is an important treatment modality for various hematological malignancies. With the widespread application of haploidentical hematopoietic stem cell transplantation (Haplo-HSCT), limitations related to donor availability have been substantially overcome. However, graft-versus-host disease (GVHD), particularly clinically significant acute GVHD, remains an important complication affecting outcomes in transplant recipients. As an oral JAK1/2 inhibitor, ruxolitinib has demonstrated clear efficacy in the treatment of steroid-refractory GVHD, although long-term outcomes following salvage therapy remain an area for further improvement. Based on its ability to regulate inflammatory signaling and T-cell activation, ruxolitinib has increasingly been investigated for early GVHD prophylaxis in recent years. However, previous evidence has mainly come from exploratory studies, with prospective randomized controlled evidence remaining limited.Recently, The Lancet Haematology published a Chinese multicenter, open-label, randomized phase III trial jointly led by Professor Yanmin Zhao, Professor He Huang, and Chief Physician Jimin Shi from the Bone Marrow Transplantation Center of the First Affiliated Hospital of Zhejiang University School of Medicine, who served as co-corresponding authors. In this study, low-dose ruxolitinib was used in place of mycophenolate mofetil (MMF) on top of a GVHD prophylaxis regimen consisting of anti-thymocyte globulin (ATG), a calcineurin inhibitor (CNI), and short-course methotrexate (MTX). The results showed that ruxolitinib significantly reduced the risk of grade II–IV acute GVHD after haploidentical HSCT, while also reducing moderate-to-severe chronic GVHD and non-relapse mortality (NRM), and significantly improving GVHD-free, relapse-free survival (GRFS).
This study provides new high-level evidence supporting the early incorporation of JAK1/2 inhibition into GVHD prophylaxis and offers important insights for further optimizing GVHD prevention strategies in haploidentical HSCT.
Study Design
Phase III Randomized Controlled Trial of Ruxolitinib Replacing MMF
This study (ClinicalTrials.gov identifier: NCT04838704) was conducted across five centers in China. Eligible patients were aged 12–70 years, had hematological malignancies requiring allogeneic HSCT, had good performance status (Karnofsky Performance Status [KPS] ≥70; Lansky score ≥70 for patients younger than 16 years), and were undergoing their first myeloablative haploidentical peripheral blood stem cell transplantation. Patients were randomly assigned in a 1:1 ratio to receive ruxolitinib-based prophylaxis or standard prophylaxis.
Both groups received a common prophylactic backbone consisting of ATG, a calcineurin inhibitor (CNI; cyclosporine or tacrolimus), and short-course methotrexate (MTX). The key difference was that low-dose ruxolitinib replaced MMF in the ruxolitinib group, whereas patients in the standard group received conventional MMF prophylaxis. Ruxolitinib was initiated on day 1 after transplantation at a dose of 5 mg twice daily for patients weighing ≥50 kg and 5 mg once daily for those weighing <50 kg. Treatment continued through day 60 and, provided that grade II–IV acute GVHD had not occurred, was gradually tapered and discontinued on day 90. The primary endpoint was the cumulative incidence of grade II–IV acute GVHD within 100 days after transplantation. Efficacy and safety were analyzed in the modified intention-to-treat (mITT) population.
Study Results
Significant Benefit in the Primary Endpoint and Broad Improvement in Long-Term Outcomes
Between April 2021 and December 2023, a total of 277 patients were screened, of whom 215 were randomly assigned to treatment. Ultimately, 206 patients (103 in each group) were included in the mITT analysis. The median recipient age was 40 years, 48% of patients were female, and the median follow-up duration was 26.4 months. Baseline characteristics were well balanced between the two groups.
The primary endpoint demonstrated a significant benefit: Within 100 days after transplantation, grade II–IV acute GVHD occurred in only 7 patients in the ruxolitinib group, corresponding to a cumulative incidence of 6.8% (95% CI, 1.9–11.7), significantly lower than the 38 cases observed in the standard prophylaxis group (36.9%; 95% CI, 27.5–46.3). The subdistribution hazard ratio (sHR) was 0.15 (95% CI, 0.07–0.34; P<0.0001), corresponding to an approximately 85% reduction in relative risk.
Organ-specific analyses showed that the incidence of grade ≥2 GVHD involving the skin (8% vs 38%), gastrointestinal tract (2% vs 19%), and liver (0% vs 3%) was also substantially lower in the ruxolitinib group. After multivariable adjustment, ruxolitinib prophylaxis remained significantly associated with a lower incidence of grade II–IV acute GVHD by day 100 (sHR, 0.15; 95% CI, 0.06–0.33; P<0.0001), with consistent findings across all prespecified subgroup analyses.
Secondary Endpoints Confirmed the Benefit, with Durable Effects
The benefits observed for the primary endpoint were consistently confirmed across secondary endpoints and remained durable over time. The cumulative incidence of grade II–IV acute GVHD at 180 days after transplantation was 10.7% in the ruxolitinib group versus 38.8% in the standard prophylaxis group (sHR=0.22, P<0.0001), with the between-group difference remaining significant at 12 months (sHR=0.22, P<0.0001). Among patients who developed acute GVHD, the median time to onset was significantly delayed in the ruxolitinib group compared with the standard group (32.5 vs 21.5 days, P=0.038).
The reduction in severe acute GVHD was even more pronounced. The cumulative incidences of grade III–IV acute GVHD at 100 days, 180 days, and 12 months were 1.9% vs 19.4% (sHR=0.09), 4.9% vs 20.4% (sHR=0.21), and 4.9% vs 21.4% (sHR=0.20), respectively, with all differences reaching statistical significance. Ruxolitinib prophylaxis also reduced the incidence of severe acute GVHD involving the skin, liver, or gastrointestinal tract.
Regarding chronic GVHD, there was no significant difference in the overall incidence between the two groups (44.1% vs 51.4%; sHR=0.79, P=0.27). However, the cumulative incidence of moderate-to-severe chronic GVHD was significantly lower in the ruxolitinib group (5.0% vs 19.1%; sHR=0.24, P=0.0024).
Long-term outcomes and safety: No non-relapse deaths occurred in the ruxolitinib group, compared with six in the standard prophylaxis group (sHR=0.16, P=0.014). There was no significant difference in cumulative relapse incidence between the two groups (15 vs 11 events; sHR=1.42, P=0.38). Relapse-free survival (HR=0.87, P=0.70) and overall survival (11 vs 14 deaths; HR=0.76, P=0.49) were comparable between groups. However, the composite endpoint of GVHD-free, relapse-free survival (GRFS) was significantly improved with ruxolitinib prophylaxis, with substantially fewer events than in the standard prophylaxis group (22 vs 47 events; HR=0.37, P<0.0001).
Engraftment and Safety
Regarding engraftment, all patients successfully achieved engraftment. The median time to neutrophil engraftment was delayed by one day in the ruxolitinib group compared with the standard prophylaxis group (12 vs 11 days, P=0.0015), while there was no significant difference in platelet engraftment between the two groups. No patients in either group experienced poor graft function.
Overall, the safety profile was manageable and comparable between the two groups, with adverse events occurring at similar rates (97% vs 98%). The most common grade 3–4 adverse events were thrombocytopenia (17% vs 11%), neutropenia (14% vs 9%), and anemia (12% vs 9%). No fatal adverse events occurred in the ruxolitinib group; the three deaths in the standard prophylaxis group were considered unrelated to the study drug.
The incidence of infectious complications was also similar between groups, including cytomegalovirus reactivation (53% vs 49%) and Epstein–Barr virus reactivation (47% vs 41%). Notably, no cases of transplant-associated thrombotic microangiopathy (TA-TMA) occurred in the ruxolitinib group.
Exploratory Analysis
Exploratory analyses showed that on day 21 after transplantation, the absolute peripheral blood counts of CD3⁺ and CD8⁺ T cells were significantly higher in the ruxolitinib group than in the standard prophylaxis group (267.9 vs 81.1 cells/μL and 173.6 vs 52.5 cells/μL, respectively). On day 14, the level of the acute GVHD biomarker ST2 was significantly lower with ruxolitinib (87.2 vs 328.3 pg/mL). These findings suggest that ruxolitinib may suppress early allogeneic inflammatory amplification while potentially supporting immune reconstitution.
Study Significance
Ushering in a Targeted Era of GVHD Prophylaxis in ATG-Based Haploidentical Transplantation
This study is the first randomized controlled phase III trial to demonstrate the efficacy of ruxolitinib for GVHD prevention in an ATG-based haploidentical HSCT platform. Several findings stand out.
First, the magnitude of benefit was unprecedented. The absolute reduction in grade II–IV acute GVHD at day 100 was approximately 30 percentage points, with consistent benefits observed in moderate-to-severe chronic GVHD, non-relapse mortality, and GRFS.
Second, the low-dose regimen balanced efficacy and safety. The dose used in this study (5 mg twice daily) was substantially lower than the doses used in REACH2 (median 16.8 mg/day) and REACH3 (10 mg twice daily). Given that cytopenias represent a dose-limiting toxicity of ruxolitinib, the low-dose strategy may help reduce hematological adverse events.
Third, the lack of an increased relapse rate helps address concerns that JAK inhibition might compromise the graft-versus-tumor (GVT) effect.
Several limitations should nevertheless be acknowledged. The study had an open-label design, enrolled exclusively Chinese patients, and its findings are applicable to ATG-based prophylaxis platforms rather than post-transplant cyclophosphamide (PTCy)-based regimens. The absence of a statistically significant overall survival benefit may be related to the study not being powered for overall survival as an efficacy endpoint. In addition, the exploratory biomarker analyses should be regarded as hypothesis-generating rather than definitive evidence. Longer follow-up, validation across different prophylaxis platforms and patient populations, and further optimization of the optimal dose and treatment duration will be necessary.
Conclusion
From its established role as salvage therapy for steroid-refractory GVHD to its emerging role in first-line post-transplant prophylaxis, ruxolitinib has undergone a notable shift in therapeutic positioning in this phase III study. With the publication of these phase III data, the ATG + CNI + short-course MTX + low-dose ruxolitinib regimen may emerge as a new prophylactic option for GVHD after haploidentical HSCT, offering renewed potential to improve transplant safety and long-term quality of life for patients with hematological malignancies.
Reference
Wu H, Shi W, Shi Z, et al. Low-dose ruxolitinib for graft-versus-host disease prevention in haploidentical haematopoietic stem-cell transplantation: a multicentre, open-label, randomised, controlled, phase 3 trial. Lancet Haematol. 2026 Aug;13(8):e533-e544. doi: 10.1016/S2352-3026(26)00167-5. PMID: 42532067.
