Encouraging results with inolimomab (anti-IL-2 receptor) as treatment for refractory acute graft-versus-host disease

Second-line therapy for patients with steroid-refractory aGVHD: systematic review and meta-analysis of randomized controlled trials

Objective

Steroids-refractory (SR) acute graft-versus-host disease (aGVHD) is a life-threatening condition in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT), but the optimal second-line therapy still has not been established. We aimed to perform a systematic review and meta-analysis of randomized controlled trials (RCTs) to compare the efficacy and safety of different second-line therapy regimens.

Methods

Literature search in MEDLINE, Embase, Cochrane Library and China Biology Medicine databases were performed to retrieve RCTs comparing the efficacy and safety of different therapy regimens for patients with SR aGVHD. Meta-analysis was conducted with Review Manager version 5.3. The primary outcome is the overall response rate (ORR) at day 28. Pooled relative risk (RR) and 95% confidence interval (CI) were calculated with the Mantel-Haenszel method.

Results

Eight eligible RCTs were included, involving 1127 patients with SR aGVHD and a broad range of second-line therapy regimens. Meta-analysis of 3 trials investigating the effects of adding mesenchymal stroma cells (MSCs) to other second-line therapy regimens suggested that the addition of MSCs is associated with significantly improvement in ORR at day 28 (RR = 1.15, 95% CI = 1.01-1.32, P = 0.04), especially in patients with severe (grade III-IV or grade C-D) aGVHD (RR = 1.26, 95% CI = 1.04-1.52, P = 0.02) and patients with multiorgan involved (RR = 1.27, 95% CI = 1.05-1.55, P = 0.01). No significant difference was observed betwwen the MSCs group and control group in consideration of overall survival and serious adverse events. Treatment outcomes of the other trials were comprehensively reviewed, ruxolitinib showed significantly higher ORR and complete response rate at day 28, higher durable overall response at day 56 and longer failure-free survival in comparison with other regimens; inolimomab shows similar 1-year therapy success rate but superior long-term overall survial in comparison with anti-thymocyte globulin, other comparisons did not show significant differences in efficacy.

Conclusions

Adding MSCs to other second-line therapy regimens is associated with significantly improved ORR, ruxolitinib showed significantly better efficacy outcomes in comparison with other regimens in patients with SR aGVHD. Further well-designed RCTs and integrated studies are required to determine the optimal treatment.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022342487.

Meta-Analysis of Interleukin-2 Receptor Antagonists as the Treatment for Steroid-Refractory Acute Graft-Versus-Host Disease

Acute graft-versus-host disease (aGVHD) is a major complication after allogeneic hematopoietic stem cell transplantation (HSCT). Corticosteroid is the first-line treatment for aGVHD, but its response rate is only approximately 50%. At present, no uniformly accepted treatment for steroid-refractory aGVHD (SR-aGVHD) is available. Blocking interleukin-2 receptors (IL-2Rs) on donor T cells using pharmaceutical antagonists alleviates SR-aGVHD. This meta-analysis aimed to compare the efficacy and safety of four commercially available IL-2R antagonists (IL-2RAs) in SR-aGVHD treatment. A total of 31 studies met the following inclusion criteria (1): patients of any race, any sex, and all ages (2); those diagnosed with SR-aGVHD after HSCT; and (3) those using IL-2RA-based therapy as the treatment for SR-aGVHD. The overall response rate (ORR) at any time after treatment with basiliximab and daclizumab was 0.81 [95% confidence interval (CI): 0.74-0.87)] and 0.71 (95% CI: 0.56-0.82), respectively, which was better than that of inolimomab 0.54 (95% CI: 0.39-0.68) and denileukin diftitox 0.56 (95% CI: 0.35-0.76). The complete response rate (CRR) at any time after treatment with basiliximab and daclizumab was 0.55 (95% CI: 0.42-0.68) and 0.42 (95%CI: 0.29-0.56), respectively, which was better than that of inolimomab 0.30 (95% CI: 0.16-0.51) and denileukin diftitox 0.37 (95% CI: 0.24-0.52). The ORR and CRR were better after 1-month treatment with basiliximab and daclizumab than after treatment with inolimomab and denileukin diftitox. The incidence of the infection was higher after inolimomab treatment than after treatment with the other IL-2RAs. In conclusion, the efficacy and safety of different IL-2RAs varied. The response rate of basiliximab was the highest, followed by that of daclizumab. Prospective, randomized controlled trials are needed to compare the efficacy and safety of different IL-2RAs.

Treatment and unmet needs in steroid-refractory acute graft-versus-host disease

Acute graft-versus-host disease (aGVHD) is a common complication of allogeneic hematopoietic stem cell transplantation (alloHCT) and is a major cause of morbidity and mortality. Systemic steroid therapy is the first-line treatment for aGVHD, although about half of patients will become refractory to treatment. As the number of patients undergoing alloHCT increases, developing safe and effective treatments for aGVHD will become increasingly important, especially for those whose disease becomes refractory to systemic steroid therapy. This paper reviews current treatment options for patients with steroid-refractory aGVHD and discusses data from recently published clinical studies to outline emerging therapeutic strategies.

Advance in Targeted Immunotherapy for Graft-Versus-Host Disease

Graft-versus-host disease (GVHD) is a serious and deadly complication of patients, who undergo hematopoietic stem cell transplantation (HSCT). Despite prophylactic treatment with immunosuppressive agents, 20–80% of recipients develop acute GVHD after HSCT. And the incidence rates of chronic GVHD range from 6 to 80%. Standard therapeutic strategies are still lacking, although considerable advances have been gained in knowing of the predisposing factors, pathology, and diagnosis of GVHD. Targeting immune cells, such as regulatory T cells, as well as tolerogenic dendritic cells or mesenchymal stromal cells (MSCs) display considerable benefit in the relief of GVHD through the deletion of alloactivated T cells. Monoclonal antibodies targeting cytokines or signaling molecules have been demonstrated to be beneficial for the prevention of GVHD. However, these remain to be verified in clinical therapy. It is also important and necessary to consider adopting individualized treatment based on GVHD subtypes, pathological mechanisms involved and stages. In the future, it is hoped that the identification of novel therapeutic targets and systematic research strategies may yield novel safe and effective approaches in clinic to improve outcomes of GVHD further. In this article, we reviewed the current advances in targeted immunotherapy for the prevention of GVHD.

Treatment Options in Steroid-Refractory Acute Graft-Versus-Host Disease Following Hematopoietic Stem Cell Transplantation

Objective:

To evaluate the treatment options in steroid-refractory acute graft-versus-host disease (GVHD) following hematopoietic stem cell transplantation.

Data Sources:

Literature was obtained by searching MEDLINE (1966–May 2007) and EMBASE (1980–May 2007).

Study Selection and Data Extraction:

All pertinent clinical trials, retrospective studies, case reports, and compassionate use studies were identified and evaluated for safety and efficacy of the pharmacologic agents.

Data Synthesis:

Steroid-refractory acute GVHD is associated with high rates of morbidity and mortality. Although various pharmacologic agents have been studied in the treatment of steroid-refractory acute GVHD, no treatments have been established as a salvage therapy. Preliminary data on different pharmacologic agents have been identified and evaluated for their efficacy and tolerability in the treatment of steroid-refractory acute GVHD. The effects of the pharmacologic agents varied significantly among patients: severity of the disease, involvement of different organs, and the patient's age seem to be the major factors that affect an individual's response to drug therapy. In addition, the treatments are further challenged by the high incidence of potentially fatal opportunistic infections that occur during the therapy.

Conclusions:

Selection of pharmacologic agents for the treatment of steroid-refractory acute GVHD should be based on the target organs, adverse drug reactions, and economic factors. Further studies with larger sample sizes are warranted to better understand the roles of these agents in the treatment of steroid-refractory acute GVHD.

A phase 3 randomized trial comparing inolimomab vs usual care in steroid-resistant acute GVHD

Treatment of steroid-resistant acute graft-versus-host disease (GVHD) remains an unmet clinical need. Inolimomab, a monoclonal antibody to CD25, has shown encouraging results in phase 2 trials. This phase 3 randomized, open-label, multicenter trial compared inolimomab vs usual care in adult patients with steroid-refractory acute GVHD. Patients were randomly selected to receive treatment with inolimomab or usual care (the control group was treated with antithymocyte globulin [ATG]). The primary objective was to evaluate overall survival at 1 year without changing baseline allocated therapy. A total of 100 patients were randomly placed: 49 patients in the inolimomab arm and 51 patients in the ATG arm. The primary criteria were reached by 14 patients (28.5%) in the inolimomab and 11 patients (21.5%) in the ATG arms, with a hazard ratio of 0.874 (P = .28). With a minimum follow-up of 1 year, 26 (53%) and 31 (60%) patients died in the inolimomab and ATG arms, respectively. Adverse events were similar in the 2 arms, with fewer viral infections in the inolimomab arm compared with the ATG arm. The primary end point of this randomized phase 3 trial was not achieved. The lack of a statistically significant effect confirms the need for development of more effective treatments for acute GVHD. This trial is registered to https://www.clinicaltrialsregister.eu/ctr-search/search as EUDRACT 2007-005009-24.

Combination Therapy with Inolimomab and Etanercept for Severe Steroid-Refractory Acute Graft-versus-Host Disease

Steroid-refractory acute graft-versus-host disease (aGVHD) remains an important cause of morbidity and mortality after allogeneic stem cell transplantation (SCT). A protocol on the management of aGVHD was introduced in our center that incorporated a prospective study on combination therapy with inolimomab (anti-IL-2Rα) and etanercept (anti-tumor necrosis factor-α) for steroid-refractory aGVHD. We evaluated the efficacy and safety in 21 consecutively treated patients. The patients had developed refractory aGVHD after SCT (n = 16) or donor lymphocyte infusion (n = 5), and aGVHD was classified as severe in all patients, mostly due to gastrointestinal involvement stages 2 to 4. No drug-related side effects were observed apart from the infections expected to occur in these severely immunocompromised patients. Overall response at day 28 of second-line therapy was 48% (10/21), with 6 and 4 patients achieving a complete and partial response, respectively. Eventually, 19 patients died (90%), with early mortality (<6 months) predominantly resulting from refractory aGVHD and secondary infections and late mortality resulting from relapse of the underlying disease. With a median follow-up of 55 days, the estimated rates of 6-month and 2-year overall survival were dismal, 29% and 10%, respectively. In conclusion, the combination of inolimomab and etanercept for steroid-refractory aGVHD failed to improve the dismal prognosis of severe steroid-refractory aGVHD.

Preemptive administration of human αβ T cell receptor-targeting monoclonal antibody GZ-αβTCR potently abrogates aggressive graft-versus-host disease in vivo

GVHD, both acute and chronic, remains the major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Thus, there is still a great need for therapeutic tools for the prevention and treatment of GVHD. Several biologics have shown promising results in salvage therapies but are attendant on an increased risk for opportunistic infections, lymphoproliferative disorders, and relapse. This is partly due to efficient T cell elimination that neither dissects alloreactive from non-alloreactive T cells nor considers functional and structural distinctiveness of pathogen- and malignancy-reactive γδ and iNKT T cells. A novel, humanized monoclonal antibody, GZ-αβTCR, specific for the human αβ T cell receptor, was evaluated in a xenogeneic GVHD model for its potential to prevent or ameliorate GVHD and prolong survival. We could show that GZ-αβTCR significantly attenuated clinical signs of GVHD and prolonged survival by preferential depletion of CD4 cells and the naïve T cell compartment, the trigger and driver of GVHD. In a regimen that included a preemptive dose, GZ-αβTCR treatment sufficiently abrogated GVHD. Importantly, GZ-αβTCR's specificity spared host cell-mediated immune competence of cell types other than αβT cells: namely γδT cells. GZ-αβTCR's outstanding capacity to prevent GVHD and ameliorate an ongoing GVHD while sparing immune cells other than αβT cells strongly recommends GZ-αβTCR for the prevention and treatment of acute GVHD in clinical settings.

Treatment and management of graft-versus-host disease: improving response and survival

Graft-versus-host disease (GVHD) is a significant cause of morbidity and mortality following allogenic haematopoietic stem-cell transplantation and thus the focus of much ongoing research. Despite considerable advances in our understanding of the pathophysiology, diagnosis and predisposing factors for both acute and chronic forms of the disease, a standardised therapeutic strategy is still lacking. There is good evidence for initial treatment of both acute and chronic forms of the disease with corticosteroid therapy. However, the most effective approach to steroid-refractory disease remains controversial, with current practice based mainly on smaller studies and varying considerably between local institutions. Timely diagnosis, multidisciplinary working and good supportive care, including infection prophylaxis, are clearly important in optimizing response and survival in such patients. It is hoped that in the future systematic research strategies and the identification of novel therapeutic targets may improve outcome further. The following review aims to outline some of the existing options for the treatment and management of acute and chronic GVHD.

Recent progress in managing graft-versus-host disease and viral infections following allogeneic stem cell transplantation

Despite recent reductions in transplant-related mortality, post-transplant complications such as graft-versus-host disease (GvHD) remain major obstacles to the successful application of allogeneic hematopoietic transplantation. Steroid-refractory GvHD has a poor outcome. Although there are a variety of new approaches to the treatment of refractory GvHD, many have limited evidence of efficacy. Other approaches appear to be unacceptably toxic. It would be preferable to improve GvHD prophylaxis. There is good evidence that rates of GvHD can be reduced without unacceptable reduction of the graft-versus-leukemia effect or compromising overall survival. However, prophylactic measures aimed at reducing T-cell numbers or functions are associated with high rates of reactivation of latent viruses. New technologies that allow rapid generation of virus-specific T-cells show promise to reduce the frequency and severity of such reactivations and have the potential to revolutionize the approach to post-transplant infectious complications.

Updated experience with inolimomab as treatment for corticosteroid-refractory acute graft-versus-host disease

Refractory acute graft-versus-host disease (aGVHD) remains an important cause of mortality after allogeneic stem cell transplantation. No standard therapy exists once steroids fail to obtain a good response. In 2006, our group published a series of patients who received inolimomab, an anti-interleukin-2 receptor monoclonal antibody, as salvage therapy with initial encouraging results. In this update, we analyzed a larger group of patients with prolonged follow-up. Ninety-two consecutive patients were treated with inolimomab at our center between April 1999 and December 2011. Overall response rate was 42% (complete response in 14%) on day +30. Predictors of failure to respond in the multivariate analysis were overall aGVHD grade IV, instauration of inolimomab before day 15 of aGVHD diagnosis, and severe lymphopenia. Patients without gastrointestinal involvement appeared to do better, with a 70% response rate compared with 39% in patients with gastrointestinal involvement (P = .06). However, the 2-year overall survival rate was of 18% for the entire cohort (95% confidence interval, 10% to 26%) and 33% for day 30 responders (95% confidence interval, 25% to 40%) and Acute GVHD was the main cause of death (49%) followed by opportunistic infections (27%). Results of this update show that although inolimomab is a well-tolerated drug with a moderate number of short-term responses, it is associated with long-term survival in only one-third of responding patients. These data highlight the need to investigate new rescue treatments with sustained effect and the importance of reporting long-term outcomes in GVHD studies.

Secondary treatment of acute graft-versus-host disease: a critical review

Management of steroid-resistant or steroid-refractory acute graft-versus-host disease (aGVHD) poses one of the most vexing and difficult problems faced by transplantation physicians. In the current study, we used 10 criteria to evaluate 67 reports describing secondary treatment of patients with aGVHD. The goal of this exercise was not only to provide a critical summary of the literature but also to offer suggestions that could improve future studies. Areas especially in need of improvement include the use of a consistent treatment regimen, the assessment of response at a consistent prespecified time point, consideration of concomitant treatment in assessing response, documentation that selection bias was minimized, and the use of methods that test a formal statistical hypothesis based on a contemporaneous or historical benchmark. Our results suggest that previous published reports collectively offer little guidance in discerning the most effective treatments for patients with steroid-resistant or steroid-refractory aGVHD. Adherence to the proposed criteria in future reports would enable meaningful comparisons across studies and thereby accelerate progress in evaluating new treatments for patients with aGVHD.

In vivo depletion of lymphotoxin-alpha expressing lymphocytes inhibits xenogeneic graft-versus-host-disease

Graft-versus-host disease (GVHD) is a major barrier to successful allogeneic hematopoietic cell transplantation and is largely mediated by activated donor lymphocytes. Lymphotoxin (LT)-α is expressed by subsets of activated T and B cells, and studies in preclinical models demonstrated that targeted depletion of these cells with a mouse anti-LT-α monoclonal antibody (mAb) was efficacious in inhibiting inflammation and autoimmune disease. Here we demonstrate that LT-α is also upregulated on activated human donor lymphocytes in a xenogeneic model of GVHD and targeted depletion of these donor cells ameliorated GVHD. A depleting humanized anti-LT-α mAb, designated MLTA3698A, was generated that specifically binds to LT-α in both the soluble and membrane-bound forms, and elicits antibody-dependent cellular cytotoxicity (ADCC) activity in vitro. Using a human peripheral blood mononuclear cell transplanted SCID (Hu-SCID) mouse model of GVHD, the anti-human LT-α mAb specifically depleted activated LT-expressing human donor T and B cells, resulting in prolonged survival of the mice. A mutation in the Fc region, rendering the mAb incapable of mediating ADCC, abolished all in vitro and in vivo effects. These data support a role for using a depleting anti-LT-α antibody in treating immune diseases such as GVHD and autoimmune diseases.

The use of monoclonal antibodies for the treatment of graft-versus-host disease following allogeneic stem cell transplantation

INTRODUCTION

Graft-versus-host disease (GVHD) remains the leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Steroids along with calcineurin inhibitors remain the standard initial therapy, however, less than half of the patients completely respond and there is no uniformly accepted therapy for patients with steroid-resistant GVHD.

AREAS COVERED

This paper reviews the current role and ongoing development of mAbs in the treatment of GVHD. Various mAbs to cell surface antigens on GVHD effector cells have been investigated for the treatment of acute GVHD: these include anti-TNF-α antibodies, IL-2 receptor antagonists, anti-CD3 and anti-CD52 mAbs, while anti-CD20 mAb has been extensively investigated in the setting of chronic GVHD. Overall, response rates have been reported to be greater than 60%, although it should be emphasized that the long-term survival still remains suboptimal, mainly due to the detrimental side effects of infectious complications, progressive GVHD and relapse of underlying malignancy.

EXPERT OPINION

Future challenges will include more appropriate definition of these agents in the therapeutic scenario of GVHD. Combinations of mAbs or mAb combined with newer immunosuppressive drugs might potentially achieve greater success, especially if used early in the disease process.

Rapamycin for refractory acute graft-versus-host disease

BACKGROUND

Rapamycin, an inhibitor of mammalian target of rapamycin kinase, is a potent immunosuppressive drug that also displays antineoplastic properties and expands regulatory T cells. Steroid-refractory acute graft-versus-host disease (GVHD) remains a significant cause of mortality after allogeneic stem-cell transplantation and therapeutic options are not codified. We retrospectively evaluated the role of rapamycin in this setting.

METHODS

In this retrospective single-center study, 22 patients were identified, from October 2004 to February 2008, as having received rapamycin for acute GVHD refractory to one or more lines of treatment. We analyzed the efficacy and tolerance of rapamycin and the outcome of these 22 patients in this setting.

RESULTS

Rapamycin resulted in a rapid and sustained complete remission of GVHD in 72% of heavily pretreated patients. Cytopenias were frequent but did not require treatment interruption. Thrombotic microangiopathy developed in 36% of patients when rapamycin was associated with calcineurin inhibitors and frequently resolved after interruption of one or both drugs. At a median follow-up of 13 months, overall survival was 41%. Previous treatment with high-dose steroid pulses was associated with a worse outcome (survival 12% vs. 69%). The major cause of death was infectious complications (77%).

CONCLUSION

Despite a small and heterogeneous population of patients, these results are encouraging and provide a rationale for prospective studies that use rapamycin in steroid-refractory acute GVHD as a second- or third-line agent.

Acute graft-versus-host disease: new treatment strategies

PURPOSE OF REVIEW

Graft-versus-host disease (GVHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT), despite improvements in our understanding of its pathophysiology as well as the generation of new monoclonal antibodies, immunomodulatory chemotherapy, cellular therapeutics and supportive care. Herein, we review therapies that have proven effective as well as newer agents that have recently improved GVHD response rates and survival following HCT.

RECENT FINDINGS

Novel approaches to prevent or treat GVHD are often based on evidence from experimental models. Our understanding of the pathophysiology of GVHD may lead to the development of innovative strategies that target both soluble and cellular effectors. Among such agents are sirolimus, anti-tumor necrosis factor antibodies, anti-LFA-3-IgG fusion protein, extracorporeal photopheresis, mesenchymal stem cells and regulatory T cells.

SUMMARY

Obstacles to the improvement of HCT include the tight linkage between GVHD toxicity and the beneficial graft-versus-leukemia (GVL) effect, as well as the impairment of immune reconstitution by immunomodulatory drugs leading to life-threatening infections. The design of newer phase I/II clinical trials are underway. Future therapies are likely to include modulation of cell types that play key roles in the GVH process, including regulatory T cells, dendritic cells, natural killer T cells and B cells.

Safety profile and clinical outcomes in a phase I, placebo-controlled study of siplizumab in acute graft-versus-host disease

BACKGROUND

Acute graft-versus-host disease (GVHD) is a major complication of both bone marrow and hematologic stem cell allografts. T cells and natural killer (NK) cells have been linked to the development of GVHD. Modulation of these cells via the CD2 receptor may be a potentially important approach to the management of this disease.

METHODS

The safety profile and tolerability of siplizumab (MEDI-507), a humanized anti-CD2 IgG-1kappa monoclonal antibody, in the treatment of GVHD were evaluated in a phase I, double-blind, multiple-dose, placebo-controlled study. Thirty-four subjects with at least grade II acute GVHD were randomized to receive four doses of 0.012, 0.04, 0.12, or 0.4 mg/kg siplizumab or placebo intravenously every 3 days. Subjects received concurrent 2 mg/kg per day methylprednisolone for more than or equal to 10 days.

RESULTS

No meaningful difference occurred between siplizumab and placebo groups in the incidence or severity of adverse events or laboratory test results. No increase in incidence of infection secondary to siplizumab treatment was observed. During 100 days postinitial infusion, a modest increase in resolution of GVHD, grade 0 (67% vs. 54%, P=0.0629), was reported for the siplizumab-treated group.

CONCLUSION

Siplizumab administered with corticosteroid therapy for grade II or higher acute GVHD treatment exhibited an acceptable safety profile that would support further clinical development.

Daclizumab therapy for children with corticosteroid-resistant acute graft-vs.-host disease

MAbs such as daclizumab have shown promising results in the treatment of corticosteroid-resistant aGVHD. Data describing the efficacy of MAbs in children are limited. We describe the efficacy of daclizumab in children with corticosteroid-resistant aGVHD. Seventeen children (0.4-16.2 yr) received daclizumab for aGVHD. Safety was evaluated in all 17. Response was evaluated in the 15 children who received a full course of daclizumab. A PR was defined as improvement of aGVHD symptoms in at least one organ without worsening in other organs. We observed an overall response rate (CR plus PR) of 40% (6/15). Four children had a CR and two had a PR. aGVHD involving the gut had the highest response rate (five of 10; 50%). Adverse effects attributed to daclizumab were limited to an episode of reactive arthritis. Mortality was high (47%; eight of 17) though five of the six responders to daclizumab survived. The mean length of follow-up in the surviving nine patients was 32 months (range seven to 48). We conclude that daclizumab is effective in the treatment of children with corticosteroid-resistant aGVHD, especially in patients with gut involvement.

Immunomodulation and pharmacological strategies in the treatment of graft-versus-host disease

BACKGROUND

Allogeneic hematopoietic stem cell transplantation offers great promise for the treatment of a variety of diseases including malignancies and other diseases of hematopoietic origin. However, morbidity and mortality due to graft-versus-host disease (GVHD) remain a major barrier to its application.

OBJECTIVE

This review will provide an overview of the pathophysiology of GVHD and discuss the recent advances in GVHD management in both preclinical and clinical studies.

METHODS

An extensive literature search on PubMed from 1995 to 2008 was performed.

RESULTS/CONCLUSION

There has been much progress in our understanding of GVHD and finding new means to control acute GVHD. While these approaches hold promise, as yet none has been able to replace the standard methods we may use routinely to decrease the incidence of the condition.

Current and novel therapies in acute GVHD

Despite improvements in our understanding of transplant immunology and clinical and supportive care, acute graft-versus-host disease (GVHD) remains a clinical challenge and a major cause of morbidity and mortality for patients after allogeneic hematopoietic stem-cell transplantation. While systemic corticosteroid is standard primary therapy for acute GVHD, there is no established standard treatment in the steroid-refractory setting. New generations of monoclonal antibodies, biologics, and chemotherapeutics with immunomodulatory effects have been developed over the past decade, and are being tested as novel therapies in this disease. Many of these agents - including, among others, mycophenolate mofetil, anti-tumor necrosis factor-alpha antibodies, denileukin diftitox, and anti-interleukin-2Ralpha-chain antibodies - have demonstrated promising activity in steroid-refractory acute GVHD. Despite the high response rates, however, long-term survival remains poor due to a high incidence of infections. The key to improving acute GVHD outcomes may, in fact, rest upon successful initial therapy, and timely taper of corticosteroids to promote healthier immune reconstitution. Clinical trials combining these newer agents with systemic corticosteroids as initial treatment are under way, and will determine whether fortifying initial therapy will indeed reduce the development of steroid-refractory GVHD and improve long-term outcomes. In this article, we review current and novel agents available for acute GVHD, and discuss newer investigational approaches - such as phototherapy and cellular therapies - in the management of this common transplant complication.