Chronic graft-versus-host disease: toward mechanism-based prevention and treatment

Chronic graft-versus-host disease (cGVHD) is a major obstacle to long-term survival after allogeneic hematopoietic stem cell transplantation (HSCT). As transplantation becomes more common, the number of survivors living with this multisystem immune-mediated disorder has increased; these patients often endure cutaneous, mucosal, gastrointestinal, and pulmonary symptoms, recurrent infections, and significant psychological distress (1,2).

cGVHD pathogenesis involves autoimmune, alloimmune, inflammatory, and fibrotic pathways that progressively damage multiple organs. Although labeled a “late” complication the biological process starts early, during conditioning. Tissue injury leads to the release of cytokines and danger signals that activate antigen-presenting cells which prime donor T cells. Concomitantly, three mechanisms entrench chronicity: a reduction in regulatory T cells (Tregs), expansion of effector memory T cells, and proliferation of autoreactive B cells producing sustained autoantibodies. These immune mediators, together with profibrotic growth factors, stimulate fibroblasts and macrophages to deposit excess collagen and extracellular matrix. The result is inflammatory and fibrotic injury across multiple organs. Such complexity necessitates therapeutic strategies that target multiple immune and stromal pathways (1).

Corticosteroids remain the first-line treatment for cGVHD; however, when the disease becomes steroid-refractory or steroid-dependent, disease control is challenging and targeted therapies are required. Over the past decade four agents have been approved that exploit distinct facets of the immune-fibrotic network: ruxolitinib, belumosudil, ibrutinib, and axatilimab (3). Each therapy has a specific mechanism, dosing schedule and evidence base that must be understood to optimize patient care.

Ruxolitinib inhibits JAK1 and JAK2, key mediators of signaling downstream of cytokine receptors such as IL-2, IL-6, and interferon-γ receptors. By blocking JAK-STAT activation, ruxolitinib reduces T-cell activation, proliferation and cytokine production (4). In the phase 3 REACH3 trial, ruxolitinib achieved a higher overall response rate at week 24 than best available therapy and provided durable benefit. The three-year final analysis demonstrated a median failure-free survival of 38.4 months with ruxolitinib versus 5.7 months with standard therapy [hazard ratio (HR) 0.36; 95%, confidence interval (CI): 0.28–0.47], and 56.5% of ruxolitinib-treated patients remained failure-free at 36 months compared with 18.2% in the control arm. Among responders, 59.6% maintained their response at 36 months. Cytopenias and infections were common but manageable; therefore, careful monitoring and dose adjustments are required (5). The robust and sustained responses observed in REACH3 have established ruxolitinib as the standard first-line therapy for steroid-refractory cGVHD. In addition, in a large multicenter study by Escamilla-Gómez et al., ruxolitinib demonstrated sustained responses and long-term efficacy in both acute and chronic GVHD among adult and pediatric patients treated outside clinical trials. Safety signals mirrored previous reports, with cytopenias and infections as the most frequent adverse events, but no unexpected toxicities emerged during extended follow-up (6).

A complementary pathway involves Rho-associated coiled-coil-containing protein kinases (ROCK), master regulators of cytoskeletal dynamics, gene expression, and cell survival that influence T-cell phenotype and fibroblast behavior. ROCK2, in particular, amplifies Th17-driven inflammation and shifts the Th17/Treg balance toward chronic immune activation. Belumosudil selectively inhibits ROCK2, rebalancing Th17/Treg populations and attenuating pro-inflammatory cytokines [interleukin (IL)-17 and IL-21 via STAT3 modulation]. It also interferes with the Rho-ROCK-MRTF axis that links cytoskeletal stress to TGF-β signaling and downstream profibrotic gene expression, thereby targeting both the inflammatory and fibrotic components of cGVHD. Two oral dosing regimens were evaluated in the phase 2 ROCKstar trial: 200 mg once daily and 200 mg twice daily. Best overall response rates were 74% and 77% for the once-daily and twice-daily arms, respectively. Responses were seen across the skin, mouth, gastrointestinal tract, liver, and lungs, with a median time to response of five weeks and >90% of responses occurring within six months. Failure-free survival at six months was approximately 75%, and the median duration of response exceeded one year in the responder group. Adverse events included hypertension, hyperglycemia, and respiratory infections; about 12% of patients discontinued therapy because of adverse events (7). Given its dual immunomodulatory and antifibrotic actions, belumosudil is a compelling option for patients with steroid refractory cGVHD, especially those with sclerotic manifestations.

Ibrutinib irreversibly inhibits Bruton tyrosine kinase, a key mediator of B-cell receptor signaling, and also targets IL-2-inducible T-cell kinase. Early studies using 420 mg orally once daily reported an overall response rate of 67% with a sustained response for >20 weeks and allowing corticosteroid tapering or discontinuation (8). However, a larger real-world cohort found that the six-month response rate was closer to 45% with modest failure-free survival. Additionally, they showed that drug discontinuation was common, 58% of the patients discontinued the treatment with ibrutinib due to progressive cGVHD or toxicity (9). A randomized phase III iNTEGRATE trial combining ibrutinib with prednisone as first-line therapy did not improve outcomes, so ibrutinib is generally reserved as a later-line option (10).

Axatilimab is a humanized IgG4 monoclonal antibody directed against the colony-stimulating factor 1 receptor (CSF-1R) expressed on monocytes and macrophages and is essential for their survival, migration, and stimulation. Macrophages in cGVHD secrete inflammatory cytokines and profibrotic mediators; by blocking CSF-1R signaling, axatilimab reduces monocyte/macrophage activation and downstream fibrosis. In the phase 2 AGAVE-201 study, overall response rates at cycle 7 day 1 were dose dependent: 74% for 0.3 mg/kg every two weeks, 67% for 1 mg/kg every two weeks and 50% for 3 mg/kg every four weeks. Symptom improvement, defined as ≥7-point reduction in the modified Lee Symptom Scale, occurred in 55%, 54% and 36% of patients in these respective cohorts. Adverse events included infusion reactions, periorbital edema, and elevations in creatine phosphokinase, liver enzymes, amylase, and lipase. Drug discontinuation due to adverse events was relatively low at 6% in the 0.3 mg/kg cohort but higher at larger doses (11,12).

Beyond small-molecule and antibody therapies, cellular therapies have emerged as a novel approach in steroid-refractory/dependent cGVHD. Tregs play a central role in immune tolerance, and impaired recovery of donor-derived Tregs is implicated in the persistence and severity of cGVHD. A combined Phase I/II donor-derived Treg infusion trial demonstrated feasibility and safety of Treg adoptive transfer in steroid-refractory or -dependent cGVHD. In this study, 33 patients received freshly isolated donor Tregs, and infusions were well-tolerated; global responses were observed in 71% of patients, with 52% achieving at least a two-point improvement on the NIH cGVHD severity scale. Importantly, improvements in cGVHD symptoms permitted reductions or discontinuation of concomitant immunosuppressive agents: corticosteroids were reduced in 58%, ruxolitinib in 83%, mycophenolate in 33%, and calcineurin inhibitors were stopped in 75% of patients. Exploratory analyses detected infused Treg clonotypes up to 12 months post-infusion and suggested increased circulating Treg numbers, supporting biological activity of the intervention (13). These findings underscore the potential utility of cellular immune modulation as a complement to pharmacologic therapy in cGVHD that is refractory to steroids. While the approach requires further validation in larger, controlled studies, Treg infusion represents a promising strategy that addresses a root immunoregulatory defect rather than only downstream inflammation or fibrosis.

Because cGVHD negatively affects quality of life, event-free survival, and overall survival, considerable efforts have been directed toward prevention. Traditional strategies have been in vivo and ex vivo T-cell depletion; however, these approaches have not eliminated cGVHD, and incidence rates remain substantial. Therefore, novel preventive strategies aim to mitigate chronic immune dysregulation while preserving the graft-versus-leukemia effect.

One of the earliest opportunities to modify cGVHD risk is to prevent acute gut injury. The gut is a major amplifier of systemic inflammation because intestinal epithelial damage allows translocation of microbial products and stimulates allogenic donor T-cells. The α4β7 integrin directs T cells to the gut via recognition of the mucosal addressin cell-adhesion molecule 1 (MAdCAM-1). Vedolizumab, a humanized monoclonal antibody, binds α4β7 integrin and blocks its interaction with MAdCAM-1 on the endothelial cells of gastrointestinal lymphoid tissue. In a randomized phase 3 trial, 333 HSCT recipients received standard GVHD prophylaxis plus either vedolizumab 300 mg or placebo on days 0 and 14. Vedolizumab significantly improved lower-gastrointestinal acute GVHD-free survival at day 180: 85.5% of vedolizumab-treated patients remained free of lower gastrointestinal acute GVHD compared with 70.9% of placebo recipients, yielding a HR of 0.45 (95% CI: 0.27–0.73). The trial confirmed that vedolizumab is well tolerated, though its long-term effect on cGVHD incidence is unknown. Because intestinal inflammation can propagate systemic immunity, early gut protection may indirectly reduce subsequent chronic disease; however, additional studies with longer follow-up are needed to confirm durable benefit (14).

Given the central role of B cells in cGVHD pathobiology, B-cell-targeted preventive strategies have also been investigated. In the latest years investigators are evaluating obinutuzumab, a glycoengineered anti-CD20 antibody with enhanced cytotoxicity, as a potential prophylactic strategy. In the randomized, double-blind NCT# 02867384 trial, 4 doses of obinutuzumab were compared with placebo in addition to tacrolimus-based primary prophylaxis. The obinutuzumab group demonstrated significantly lower rates of steroid-requiring cGVHD at 12 months post-transplant compared with placebo (11% vs. 38%, P=0.008) (15).

Ruxolitinib, an oral JAK1/2 inhibitor, dampens the JAK-STAT pathway downstream of multiple pro-inflammatory cytokines, thereby curbing T-cell activation, trafficking, and cytokine output (4). Beyond salvage therapy, ruxolitinib has also been evaluated as a preventive strategy. In a prospective, multicenter phase II study (NCT03286530), maintenance ruxolitinib was started between day +30 and +100 after reduced-intensity HSCT (with tacrolimus/methotrexate prophylaxis) and continued in 28-day cycles for up to 24 cycles. Among patients who received ruxolitinib (median start day +45), the most common grade ≥3 adverse events were neutropenia, thrombocytopenia, and anemia, with some severe infections. Outcomes were encouraging: one-year GVHD-free, relapse-free survival reached approximately 70%; grade III–IV acute GVHD at 6 months was 4.8%, and moderate-to-severe cGVHD at 2 years was 16%, with systemic therapy needed in 10–13% by one to two years. Two-year overall and progression-free survival were 76% and 68%, respectively (16). Taken together, these findings support continued exploration of peri-transplant JAK inhibition within prophylaxis strategies. These data reinforce ruxolitinib as a standard second-line option in routine practice while suggesting a potential preventive role.

Integrating these agents into practice requires careful consideration of both mechanism and timing. Combining gut-homing inhibition with B-cell depletion or costimulation blockade may reduce acute GVHD and thereby lower chronic risk, but excessive early immunosuppression could increase infection and relapse. Personalizing prophylaxis according to donor type, conditioning intensity, and individual immune risk profiles may optimize outcomes. Maintenance JAK inhibition may preserve immune surveillance while suppressing cytokine signaling, but no single agent prevents all cGVHD, so multimodal approaches are needed.

For established cGVHD, sequential or combination therapy may optimize outcomes. Ruxolitinib should be considered the backbone for second-line treatment given its proven durability; however, not all patients respond or maintain responses. Switching to belumosudil may be rational in cases characterized by prominent fibrosis and Th17/Treg disbalance, and early data suggest that sequential therapy after JAK inhibition is feasible. Axatilimab offers another option for patients with fibrotic or macrophage-driven disease and may be particularly useful after multiple prior lines given its distinct mechanism and favorable toxicity profile. Ibrutinib may still benefit selected patients with prominent B-cell involvement or those who cannot tolerate other agents, but its modest real-world efficacy warrants caution use. Combination regimens, such as ruxolitinib plus belumosudil (17) or ruxolitinib plus axatilimab (18), are appealing because they target complementary immune pathways; however, additive toxicity must be carefully monitored and prospective trials are required. Importantly, supportive measures such as infection prophylaxis, vaccination, physical therapy and psychosocial support remain critical to improving quality of life for cGVHD patients.

Looking ahead, the field is moving toward personalized, mechanism-driven prophylaxis and treatment strategies (Figure 1). Biomarker-based risk stratification could identify patients who would benefit most from early integrin blockade, costimulation inhibition or B-cell depletion. Longitudinal immune profiling may reveal which pathways are dominant at various stages, guiding the choice and sequence of targeted agents. Emerging cellular therapies may further improve outcomes by restoring immune tolerance and preventing fibrosis.

Figure 1 Pathogenesis, prevention and treatment strategies for steroid-refractory or steroid-resistant GVHD. Chronic GVHD arises following tissue injury induced by conditioning regimens, leading to the release of inflammatory cytokines and DAMPs. These signals activate host APC, which migrate to lymphoid organs and prime donor-derived T cells. Activated T cells recognize the antigens and infiltrate multiple target tissues, while concomitant immune dysregulation (characterized by reduced Treg, expansion of effector memory and Th17 cells and expansion of autoreactive B cells) drives chronic inflammation and fibrosis. The incidence of cGVHD remains significant despite conventional preventive approaches; consequently, emerging strategies seek to attenuate chronic immune dysregulation while preserving the graft-versus-leukemia effect. The figure highlights selected contemporary prophylactic interventions, including vedolizumab (which inhibits α4β7-mediated T-cell homing to the gastrointestinal tract), obinutuzumab (a B-cell-depleting anti-CD20 monoclonal antibody), and ruxolitinib (a JAK1/2 inhibitor that suppresses pathogenic T-cell activation). When neither preventive strategies nor corticosteroid therapy are sufficient, four treatments approved by the U.S. Food and Drug Administration are available for the management of cGVHD, as shown in the third column. These agents include belumosudil (a selective ROCK2 inhibitor that modulates Th17/Treg differentiation and reduces profibrotic signaling), ibrutinib (a BTK inhibitor that suppresses B-cell activation), axatilimab (a monoclonal antibody targeting CSF-1R that attenuates macrophage-driven profibrotic signaling) and ruxolitinib (previously described). Original figure. Created in https://BioRender.com. APC, antigen-presenting cells; BTK, Bruton tyrosine kinase; cGVHD, chronic graft‑versus‑host disease; CSF-1R, colony-stimulating factor 1 receptor; DAMPs, damage-associated molecular patterns; MAdCAM‑1, mucosal addressin cell‑adhesion molecule 1; Treg, regulatory T cells.

In conclusion, cGVHD stems from conditioning-induced tissue injury and subsequent dysregulation of immune and fibrotic pathways. Early prophylaxis with vedolizumab, rituximab or obinutuzumab and possibly ruxolitinib maintenance may blunt the priming events that lead to chronic disease. For established cGVHD, mechanistic therapies such as ruxolitinib, belumosudil, axatilimab and, in selected cases, ibrutinib provide meaningful control. The future of cGVHD management will rely on personalized, multimodal approaches guided by biomarkers and ongoing clinical research to optimize prevention and treatment while preserving the graft-versus-leukemia effect.

Acknowledgments

The authors gratefully acknowledge all foundations that support the fight against cancer, especially Fundación Cris Contra el Cáncer and Fundación Caíco, for their dedication and invaluable contribution to advancing cancer research and patient care.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Annals of Blood. The article has undergone external peer review.

Peer Review File: Available at https://aob.amegroups.com/article/view/10.21037/aob-2025-1-61/prf

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://aob.amegroups.com/article/view/10.21037/aob-2025-1-61/coif). The authors have no conflicts of interest to declare.

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