Abstract

Despite major advances in recent years, graft-versus-host disease (GVHD) remains a major life-threatening complication of allogeneic hematopoietic cell transplantation (allo-HCT). To improve our therapeutic armory against GVHD, preclinical evidence is most frequently generated in mouse and large animal models of GVHD. However, because every model has shortcomings, it is important to understand how predictive the different models are and why certain findings in these models could not be translated into the clinic. Weaknesses of the animal GVHD models include the irradiation only-based conditioning regimen, the homogenous donor/recipient genetics in mice, canine or non-human primates (NHP), anatomic site of T cells used for transfer in mice, the homogenous microbial environment in mice housed under specific pathogen-free conditions, and the lack of pharmacologic GVHD prevention in control groups. Despite these major differences toward clinical allo-HCT, findings generated in animal models of GVHD have led to the current gold standards for GVHD prophylaxis and therapy. The homogenous nature of the preclinical models allows for reproducibility, which is key for the characterization of the role of a new cytokine, chemokine, transcription factor, microRNA, kinase, or immune cell population in the context of GVHD. Therefore, when carefully balancing reasons to apply small and large animal models, it becomes evident that they are valuable tools to generate preclinical hypotheses, which then have to be rigorously evaluated in the clinical setting. In this study, we discuss several clinical approaches that were motivated by preclinical evidence, novel NHP models and their advantages, and highlight the recent advances in understanding the pathophysiology of GVHD.

Introduction

Our understanding of the roles of the innate immune system, the adaptive immune system, and different epithelial and antigen-presenting cell types in graft-versus-host disease (GVHD) pathogenesis has made major advances over the last 2 decades. Despite these advances and the prophylactic treatment with a wider array of immunosuppressive medication, ∼50% of the patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT) develop grade 2-4 acute GVHD (aGVHD).1  aGVHD patients who are refractory to standard steroid treatment have a dismal long-term prognosis with only 5% to 30% overall survival (OS).2-4  Chronic GVHD (cGVHD) causes high morbidity, reduces the quality of life, and is associated with a significantly higher risk of treatment-related mortality and inferior OS.5  Clinical experience teaches that aGVHD and cGVHD in humans are multilayer diseases, which are hard to treat once they are fully established. The immunologic complexity of the disease and the role of donor and recipient cell types has been the focus of intensive research.6-10 

In this review we discuss different prophylactic and therapeutic approaches against aGVHD and cGVHD that have been developed in preclinical models and analyze how successful these approaches were later in clinical trials. We divide the preclinical approaches into pharmacologic and cellular therapy strategies and connect them to the resulting clinical studies. Additionally, promising novel approaches in mice and non-human primate (NHP) models of GVHD that have not yet entered clinical studies will be discussed.

Pharmacologic prophylaxis and therapy of aGVHD

Basics of aGVHD prophylaxis and therapy

The basic pharmacologic aGVHD prophylaxis with cyclosporine A (CyA) and methotrexate (MTX) that is still used in a large proportion of the currently applied immunosuppressive regiments following allo-HCT was first studied in the dog model, where it showed potent inhibitory effects on aGVHD.11  The studies in dogs were followed by a clinical study that revealed that the combination of CyA and MTX was superior to CyA alone with respect to protection from GVHD and survival, and therefore the calcineurin inhibitor CyA became the gold standard for GVHD prophylaxis.12  Later, the combination of tacrolimus and MTX after unrelated allo-HCT was shown to significantly decrease the risk for aGVHD, but not OS and relapse-free survival rates compared with CyA and MTX,13  and therefore both CyA and tacrolimus are the backbone of most immunosuppressive regimens for patients currently undergoing allo-HCT worldwide. Another established component for aGVHD prophylaxis is anti-thymocyte globulin (ATG), which was initially reported to be protective against GVHD in the canine model.14  Different types of ATG exist and for rabbit anti-thymocyte globulin Fresenius (ATG-F), a randomized, open-label, multicenter phase 3 trial was performed that showed a decreased incidence of aGVHD and cGVHD without an increase in relapse or nonrelapse mortality (NRM) when ATG-F was added to the standard GVHD prophylaxis.15  This was extended recently by a multicenter trial showing that the rate of a composite end point of cGVHD-free survival and relapse-free survival was higher with ATG.16  Besides ATG-F, thymoglobulin was also shown to be protective against GVHD.17  Steroids currently represent the gold-standard treatment of aGVHD based on multiple prospective trials.18,19  Early evidence supporting the use of corticosteroids against aGVHD was provided in the 1990s in a haploidentical parent into F1 mouse models of GVHD.20,21 

Cytokine and chemokine inhibition as acute aGVHD prophylaxis and therapy

To avoid the broad spectrum of side effects caused by corticosteroids and to be able to offer a therapeutic option for patients with GVHD that had failed corticosteroids, the role of multiple cytokines in the pathophysiology of aGVHD was investigated in the mouse model. Interleukin-11 (IL-11),22,23  IL-1β,24 tumor necrosis factor-α (TNF-α),25,26  and IL-627,28  among others were targeted in mouse models of GVHD leading to later clinical studies. In the mouse model of GVHD, IL-11 promoted T-cell polarization toward a T helper 2 (Th2) phenotype, was associated with a lower level of IL-12, and reduced GVHD-related mortality.22,23  Consequently, recombinant human IL-11 was then investigated in a phase 1/2 double-blind, placebo-controlled study for mucositis and aGVHD prevention.29  Of 10 evaluable patients who received IL-11 in this trial, 4 died by day 40 and 1 died on day 85 due to transplant-related toxicity.29  The major adverse side effect in patients receiving IL-11 was severe fluid retention that caused pulmonary edema.29  This trial was not able to determine whether IL-11 given in this schedule can reduce the rate of GVHD. The unexpected high mortality showed that a cytokine that was well-tolerated by the mice induced severe side effects in humans, sounding a note of caution for investigators translating findings from preclinical models into a trial on humans. IL-1β was shown to be a proinflammatory cytokine in intestinal inflammation,30  to be released upon tissue damage causing Nlrp3 inflammasome activation,31,32  which is connected to impaired suppressor function of myeloid-derived suppressor cells33  and to promote the severity of aGVHD in the mouse model.24  Conversely, other studies in major histocompatibility complex (MHC) disparate mouse models showed only a very modest effect of IL-1 antagonists.34  Although initial studies using IL-1 antagonism in the therapeutic setting suggested a benefit for patients suffering from GVHD,24,35  the later prospective, randomized, controlled trial failed to show a benefit from IL-1 blockade administered from day −4 to day +10 relative to allo-HCT.36  In different mouse models of GVHD, TNF-α antagonism reduced GVHD severity.37-39 

The murine studies showed that TNF-α was derived from donor T cells, regulated by microRNA-146a/TRAF638  and myeloid cells.25  Mechanistically, TNF-α was shown to directly damage the intestinal epithelium25,26  and to downmodulate the function of regulatory T cells (Tregs),39  which protect against GVHD.40-42  Consequently, clinical studies using TNF-α antagonism with etanercept43  or infliximab44  in the therapeutic setting against GVHD were performed. Infliximab in addition to steroids reduced GVHD severity; however, the reported NRM was unexpectedly high.44  Etanercept given as a combination therapy with inolimomab (anti–IL-2Rα) for the treatment of steroid-refractory aGVHD yielded a response rate of 48%.43  However, the estimated rates of 6-month and 2-year OS were 29% and 10%, respectively, leading the authors to conclude that the combination failed to improve the dismal prognosis of severe steroid-refractory aGVHD.43  These unfavorable results of TNF-α blockade are connected to a high NRM and relapse, which is consistent with reports showing a high incidence of fungal infections45  and reduced graft-versus-leukemia (GVL) effects46  when TNF-α is antagonized. These findings could have been predicted by mouse studies as TNF antagonism reduced GVL effects against P815 cells.25  IL-6 blockade was shown to potently reduce aGVHD in mice27,28  and with the availability of the IL-6R antagonist tocilizumab, a prospective single-institution phase 1/2 aGVHD prophylaxis trial was performed.47  This study showed an incidence of grade 2-4 aGVHD in patients treated with tocilizumab at day 100 of 12%, which is lower than expected.47  These results are very promising, and several controlled trials assessing tocilizumab in addition to standard GVHD prophylaxis or as GVHD therapy are currently active (www.clinicaltrials.gov: #NCT01757197, #NCT02447055, #NCT02206035, and #NCT02057770).

Besides cytokines that promote the activation of T cells, chemokines that guide the migration of T cells toward GVHD target organs were identified as a pharmacologic target in mouse models of aGVHD.48,49  However, this strategy is seen controversial as high radiation can break the principles of chemokine-mediated selected tissue migration and trapping. For example, CCR5 inhibition was protective against GVHD in a non-irradiated GVHD mouse model,48  whereas in the presence of total body irradiation (TBI) an earlier time to onset and a worsening of GVHD was observed when CCR5−/− T cells were used.50  This knowledge was later applied in a GVHD prophylaxis setting where a single institution phase 1 trial reported that CCR5 inhibition prevents aGVHD of the liver and gut before day 100,51  which has to be confirmed in a randomized prospective multicenter study. However, recent data using CCR5 inhibition in the setting of reduced-intensity conditioning revealed no protection from GVHD.52  Therefore, the potential efficacy of CCR5 inhibition may be context dependent and has yet to be fully tested. Inhibition of T-cell egress from the lymph node53,54  and dendritic cell (DC) migration55  was potently inhibited by the sphingosine 1-phosphate receptor agonist FTY720 in the mouse model of GVHD, a therapeutic concept that is currently investigated by using KRP-203, the sphingosine 1-phosphate receptor type 1 agonist,56  in a clinical study on patients undergoing allo-HCT (www.clinicaltrials.gov: #NCT01830010) with the advantage that upon discontinuation of the drug, T-cell effector function can be unleashed from suppression,57  as has been demonstrated for rodent T-effector responses in allo-bone marrow (BM) transplantation.18 

Besides blocking T-cell migration, the co-stimulation of T cells was recognized as a potential powerful target during aGVHD. In the 1990s, it was shown that CTLA4-immunoglobulin (Ig) reduces lethal murine GVHD,58  which later motivated a trial showing that CD28:CD80/86 co-stimulation blockade with abatacept leads to low GVHD rates.59  The opponent of CTLA4-Ig, the CTLA-4 blocking antibody ipilimumab was recently applied in the posttransplant setting for patients with refractory malignancies and did not lead to an unacceptable high GVHD rate when given at a median of 1 year (range, 125-2368 days) after the last allogeneic cell infusion.60  Recent studies on another negative regulator of T-cell activation, namely programmed death-1 using checkpoint inhibition showed promising results in the mouse model61,62  that should be further investigated in the clinic.

The multiple approaches developed from the mouse model into a clinical application for aGVHD are summarized in Figure 1 and the summary of translation of each application is provided in Tables 1 and 2.

Figure 1

aGVHD. Simplified sketch showing the mode of action of multiple immunosuppressive strategies that were all developed from animal models into a clinical application for aGVHD. Ab, antibody; ECP, extracorporal photophoresis; ITAM, immunoreceptor tyrosine-based activation motif; MMF, mycophenolate mofetil; MSC, mesenchymal stroma cells; mTOR, mammalian target of rapamycin complex; NKT, natural killer T cells.

Figure 1

aGVHD. Simplified sketch showing the mode of action of multiple immunosuppressive strategies that were all developed from animal models into a clinical application for aGVHD. Ab, antibody; ECP, extracorporal photophoresis; ITAM, immunoreceptor tyrosine-based activation motif; MMF, mycophenolate mofetil; MSC, mesenchymal stroma cells; mTOR, mammalian target of rapamycin complex; NKT, natural killer T cells.

Table 1

Translation of immunosuppressive strategies from animal models of GVHD into clinical trials

Main conclusion from the preclinical model of GVHD (y) Reference Main conclusion from the clinical trials (y) Reference 
CyA and MTX reduce GVHD in the canine GVHD model (1982) 11  MTX and CyA is superior to CyA alone for GVHD prophylaxis (1986). Phase 3 prospective, randomized trial 12  
ATG prevents GVHD in DLA haplotype mismatched littermate dogs (1979) 14  Different types of ATG reduce the risk of acute and cGVHD in patients (1979, 2009, 2016). Phase 3 prospective, randomized trials (2009, 2016) 15,16,127  
Corticosteroids reduce GVHD severity in mice (1990, 1995) 20,21  Corticosteroids are effective as first-line therapy for aGVHD in patients (1998, 2009). Phase 3 multicenter randomized trial (1998); retrospective analysis (2009) 18,19  
IL-11 downregulated IL-12, and reduced aGVHD-related mortality (1998, 1999) 22,23  IL-11 leads to increased mortality in patients (2002). Phase 1/2 double-blind, placebo-controlled study 29  
IL-1 blockade reduces GVHD in mice in some but not all models (1991) 24  IL-1 antagonist is not effective in the GVHD prophylaxis setting (2002). Phase 3 prospective placebo-controlled study 36  
TNF-α antagonism reduces GVHD (1999, 2003) 25,26  Infliximab and corticosteroids are effective as initial treatment of GVHD. Prospective phase 3 study (2009); retrospective analysis (2011) 44,128  
IL-6 blockade reduces aGVHD in mice (2009, 2011) 27,28  Early IL-6 inhibition with tocilizumab leads to a low risk of aGVHD (2014). Phase 1/2 single institution trial 47  
Anti-CCR5 antibody treatment protects against aGVHD-related mortality (1999, 2003) 48,49  CCR5 inhibition prevents aGVHD of liver and gut before day 100 (2012). Phase 1/2 single institution trial 129  
The sphingosine 1-phosphate receptor agonist FTY720 reduces GVHD (2003, 2007) 53,54  Active clinical study on KRP203 in patients undergoing allo-HCT (2016). Randomized, open-label phase 1/2 study 57  
CTLA4-Ig reduces lethal murine GVHD (1994) 58  CD28:CD80/86 co-stimulation blockade with abatacept leads to low GVHD rates (2013). Single-arm feasibility study 59  
KGF reduces but does not uniformly eliminate GVHD lethality in mice (1998, 1999) 63,64  Palifermin does not reduce aGVHD severity (2012) but there is a need for parenteral nutrition after TBI (2013). Radomized, double-blind, placebo-controlled trial (2012); retrospective analysis (2013) 65,66  
Memory CD4+ T cells cause less aGVHD and cGVHD (2003, 2007, 2009) 68,69,113  Naive T-cell–depleted stem cell graft transfer is connected to less cGVHD and no change aGVHD incidence though more steroid responsiveness (2015). Single-arm, 2 site clinical trial 70  
Photoinactivation of T-cell function with psoralen and UV radiation suppresses GVHD in mice (1991) 71  ECP is an effective therapy for aGVHD (2000, 2015). Pilot study (2000); meta-analysis of prospective studies for ECP (2015) 72,73  
Statins reduce GVHD severity (2007, 2009) 75,76  Statin intake is connected to reduced GVHD incidence in patients (2010, 2010, 2013). Retrospective analysis (2010); prospective phase 2 trial, donor and recipient treatment (2013) 77,78-79  
HDAC inhibition reduced GVHD severity in mice (2008) 81  Vorinostat in combination with standard GVHD prophylaxis is associated with a low incidence of severe aGVHD (2014). 82  
Phase 1/2 trial 
JAK1/2 inhibition reduces aGVHD (2014, 2015) 83,84  JAK1/2 inhibition reduces aGVHD in patients refractory to multiple therapies (2015). Retrospective analysis 85  
Proteasome inhibition with bortezomib reduces GVHD (2004) 87  Short-course, bortezomib-based GVHD prophylaxis yields low aGVHD rates (2009, 2012). Phase 1 trial (2009); prospective phase 1/2 trial (2012) 88,89  
α-GalCer reduces GVHD (2005) 92  RGI-2001 is tested for GVHD prevention (2016). Phase 1/2 trial 51  
CP can induce tolerance toward skin allografts (1989)93  and posttransplant CP reduced GVHD severity in mice (2014)95  93,95  Posttransplantation CP is effective as single-agent aGVHD prophylaxis (2014). Open label multi-institutional trial 97,98  
Main conclusion from the preclinical model of GVHD (y) Reference Main conclusion from the clinical trials (y) Reference 
CyA and MTX reduce GVHD in the canine GVHD model (1982) 11  MTX and CyA is superior to CyA alone for GVHD prophylaxis (1986). Phase 3 prospective, randomized trial 12  
ATG prevents GVHD in DLA haplotype mismatched littermate dogs (1979) 14  Different types of ATG reduce the risk of acute and cGVHD in patients (1979, 2009, 2016). Phase 3 prospective, randomized trials (2009, 2016) 15,16,127  
Corticosteroids reduce GVHD severity in mice (1990, 1995) 20,21  Corticosteroids are effective as first-line therapy for aGVHD in patients (1998, 2009). Phase 3 multicenter randomized trial (1998); retrospective analysis (2009) 18,19  
IL-11 downregulated IL-12, and reduced aGVHD-related mortality (1998, 1999) 22,23  IL-11 leads to increased mortality in patients (2002). Phase 1/2 double-blind, placebo-controlled study 29  
IL-1 blockade reduces GVHD in mice in some but not all models (1991) 24  IL-1 antagonist is not effective in the GVHD prophylaxis setting (2002). Phase 3 prospective placebo-controlled study 36  
TNF-α antagonism reduces GVHD (1999, 2003) 25,26  Infliximab and corticosteroids are effective as initial treatment of GVHD. Prospective phase 3 study (2009); retrospective analysis (2011) 44,128  
IL-6 blockade reduces aGVHD in mice (2009, 2011) 27,28  Early IL-6 inhibition with tocilizumab leads to a low risk of aGVHD (2014). Phase 1/2 single institution trial 47  
Anti-CCR5 antibody treatment protects against aGVHD-related mortality (1999, 2003) 48,49  CCR5 inhibition prevents aGVHD of liver and gut before day 100 (2012). Phase 1/2 single institution trial 129  
The sphingosine 1-phosphate receptor agonist FTY720 reduces GVHD (2003, 2007) 53,54  Active clinical study on KRP203 in patients undergoing allo-HCT (2016). Randomized, open-label phase 1/2 study 57  
CTLA4-Ig reduces lethal murine GVHD (1994) 58  CD28:CD80/86 co-stimulation blockade with abatacept leads to low GVHD rates (2013). Single-arm feasibility study 59  
KGF reduces but does not uniformly eliminate GVHD lethality in mice (1998, 1999) 63,64  Palifermin does not reduce aGVHD severity (2012) but there is a need for parenteral nutrition after TBI (2013). Radomized, double-blind, placebo-controlled trial (2012); retrospective analysis (2013) 65,66  
Memory CD4+ T cells cause less aGVHD and cGVHD (2003, 2007, 2009) 68,69,113  Naive T-cell–depleted stem cell graft transfer is connected to less cGVHD and no change aGVHD incidence though more steroid responsiveness (2015). Single-arm, 2 site clinical trial 70  
Photoinactivation of T-cell function with psoralen and UV radiation suppresses GVHD in mice (1991) 71  ECP is an effective therapy for aGVHD (2000, 2015). Pilot study (2000); meta-analysis of prospective studies for ECP (2015) 72,73  
Statins reduce GVHD severity (2007, 2009) 75,76  Statin intake is connected to reduced GVHD incidence in patients (2010, 2010, 2013). Retrospective analysis (2010); prospective phase 2 trial, donor and recipient treatment (2013) 77,78-79  
HDAC inhibition reduced GVHD severity in mice (2008) 81  Vorinostat in combination with standard GVHD prophylaxis is associated with a low incidence of severe aGVHD (2014). 82  
Phase 1/2 trial 
JAK1/2 inhibition reduces aGVHD (2014, 2015) 83,84  JAK1/2 inhibition reduces aGVHD in patients refractory to multiple therapies (2015). Retrospective analysis 85  
Proteasome inhibition with bortezomib reduces GVHD (2004) 87  Short-course, bortezomib-based GVHD prophylaxis yields low aGVHD rates (2009, 2012). Phase 1 trial (2009); prospective phase 1/2 trial (2012) 88,89  
α-GalCer reduces GVHD (2005) 92  RGI-2001 is tested for GVHD prevention (2016). Phase 1/2 trial 51  
CP can induce tolerance toward skin allografts (1989)93  and posttransplant CP reduced GVHD severity in mice (2014)95  93,95  Posttransplantation CP is effective as single-agent aGVHD prophylaxis (2014). Open label multi-institutional trial 97,98  

CP, cyclophosphamide; DLA, dog leukocyte antigen.

Table 2

Translation of cellular therapies from aGVHD mouse models into clinical trials

Main conclusion from the mouse model of GVHD Reference Clinical trial Reference 
Treg transfer reduces GVHD (2002, 2003) 40,42,100  Treg transfer is associated with low GVHD rates (2011, 2011, 2016). Open label and phase 1 trials 101,102-103  
Th2 cells generated by rapamycin exposure cause GVHD protection (2005) 107  Rapamycin-resistant donor CD4+ Th2/Th1 transfer after allo-HCT is well-tolerated and connected to low aGVHD day 100 (2013). Phase 2 clinical trial 108  
MSCs reduce GVHD (2012) 130  MSC reduces GVHD in open-label studies and phase 2 trials (2004, 2014) 110,111  
Main conclusion from the mouse model of GVHD Reference Clinical trial Reference 
Treg transfer reduces GVHD (2002, 2003) 40,42,100  Treg transfer is associated with low GVHD rates (2011, 2011, 2016). Open label and phase 1 trials 101,102-103  
Th2 cells generated by rapamycin exposure cause GVHD protection (2005) 107  Rapamycin-resistant donor CD4+ Th2/Th1 transfer after allo-HCT is well-tolerated and connected to low aGVHD day 100 (2013). Phase 2 clinical trial 108  
MSCs reduce GVHD (2012) 130  MSC reduces GVHD in open-label studies and phase 2 trials (2004, 2014) 110,111  

Targeting multiple layers of aGVHD

In contrast to the approaches against GVHD that aim at targeting T cells or their cytokines, other studies were performed in the 1990s that aimed at improving the regeneration of the epithelial barrier by using a growth factor called keratinocyte growth factor (KGF).63,64  KGF reduced aGVHD in mouse models as shown by different groups.63,64  However, the survival benefit did vary between the different reports, raging from a modest improvement of the survival63  to highly protective effects.64  The drug palifermin did not reduce aGVHD in patients, but it did reduce the need for parenteral nutrition after TBI.65,66  The concept of enhancing epithelial regeneration via stimulation of intestinal stem cells, eg, via R-spondin-167  is still actively investigated and may have the advantage of sparing GVL effects as donor T cells are not blocked.

Another approach aimed at leaving effector T cells that mediate GVL effects intact was based on studies in the mouse model of aGVHD showing that memory CD4+ T cells cause less or almost no aGVHD but mediate GVL effects.68,69,113  The clinical study showed that the use of naive T-cell–depleted stem cell grafts with tacrolimus only suppression was connected to the same incidence of but more steroid responsive aGVHD, along with a markedly reduced cGVHD incidence, the latter consistent with rodent studies of Tn depletion in a cGVHD model.70,113  An early study performed in 1991 in mice showed that photoinactivation of T-cell function with psoralen and UV radiation suppresses aGVHD.71  Meanwhile, extracorporal photophoresis has become an important treatment option for patients with aGVHD.72,73  Statins that inhibit the rate-limiting enzyme of the l-mevalonate pathway were shown to reduce farnesyl- and geranylgeranyl-residues that are required for the correct attachment of different small GTPases to the cell membrane and thereby modulate the allogeneic immune response.74  Consistently different independent groups could show that statins reduce aGVHD in mouse models.75,76  In patients undergoing allo-HCT, some studies showed that statin intake by the donor77  or host78  was connected to a reduced GVHD incidence,77-79  whereas another trial showed that the addition of atorvastatin to standard aGVHD prophylaxis did not provide a benefit with respect to GVHD rates.80  Comparable to statins that have a broad range of inhibitory effects, histone deacetylase (HDAC) inhibitors were shown to modify multiple layers of the allogeneic immune response. Mechanistically, it was shown that not only the phenotype of T cells was polarized toward Tregs but also that DCs treated ex vivo with HDAC inhibitors displayed increased expression of indoleamine 2,3-dioxygenase, which reduces both DC and T-cell function.81  Consistently, administration of the HDAC inhibitor vorinostat in combination with standard aGVHD prophylaxis in a phase 1/2 study after related-donor reduced-intensity conditioning allo-HCT was associated with a relatively low incidence of grade 2-4 aGVHD by day 100 of 22%.82 

Signaling of multiple cytokine receptors requires intact Janus kinase 1/2 (JAK1/2) activity (Figure 1) and different groups could show that pharmacologic inhibition of JAK1/2 reduced aGVHD in the mouse.83,84  In a retrospective survey, 19 stem cell transplant centers in Europe and the United States reported their data on the use of the JAK1/2 inhibitor ruxolitinib for steroid refractory GVHD.85  The overall response rate was 81.5% (44/54) in steroid refractory aGVHD including 25 complete responses (46.3%), whereas for steroid refractory cGVHD the overall response rate was 85.4% (35/41), consistent with data in a cGVHD mouse model.85  Ruxolitinib will be investigated in a prospective trial in Germany (#NCT02396628) and a clinical trial using the JAK1 selective inhibitor INCB39110 has begun for the treatment of GVHD (#NCT02614612). Potential differences between JAK1 and JAK2 inhibition include a potentially lower risk of cytopenia when only JAK1 is inhibited, although this may come with a reduced efficacy as JAK2 inhibition alone was shown to reduce GVHD. Also, a recent study suggests that topical ruxolitinib suppresses GVHD and protects skin follicular stem cells, whereas topical corticosteroids inhibit skin stem cells and niche pre-adipocytes.86  A promising approach to reduce aGVHD is the proteasome inhibitor bortezomib that was shown to reduce aGVHD in the mouse model.87  Mechanistically bortezomib inhibits nuclear factor-κB, thereby reducing inflammatory protein production. Clinical studies using a short-course, bortezomib-based GVHD prophylaxis yielded low aGVHD rates.88,89 

α-GalCer is a glycolipid that functions as a CD1d ligand. Because α-GalCer was found to expand and activate natural killer T cells, and subsequently Tregs,90  it was developed as an immune modulator. Preclinical models have demonstrated efficacy of α-GalCer in many autoimmune disorders and GVHD.91,92  Although inhibition was found when the N-acyl variant C20:2 was used, another form of α-GalCer exacerbated GVHD.91  Based on these preclinical studies, the liposomal formulation of α-GalCer named RGI-2001 is currently investigated in a phase 1/2a, open-label, multicenter, dose-escalation study for patients undergoing allo-HCT (www.clinicaltrials.gov: #NCT01379209).51 

An important observation made in murine BM chimera was that CP given on day 2 after transplantation induced tolerance toward skin allografts.93  The authors concluded that the form of CP posttransplantation conditioning most likely decreased the number of MHC-alloreactive T cells.93  Consistent with that concept, analyses of T-cell receptor Vβ subunits that recognize endogenous super-antigens in disparate murine allo-combinations showed that CP deletes alloreactive T cells.94  Posttransplant CP reduced aGVHD severity in mice in a Treg-dependent manner, which was shown by using transgenic mice in whom Foxp3+ Tregs can be selectively depleted.95  In patients, it was shown that posttransplant CP is highly effective in preserving human Tregs, and in aGVHD prophylaxis96  when used in combination with sirolimus or as a single agent.97-99  The multiple approaches developed from the mouse model into a clinical application for aGVHD are summarized in Figure 1.

A goal of preclinical models is to develop new approaches to prevent and treat GVHD. Although numerous reagents and cell therapies have progressed from preclinical studies into clinical trials, these were predominantly phase 1 and 2 studies. Alternatively, some approaches have been moved into the clinic based upon biological underpinnings and targets without in vivo preclinical testing. Although both approaches have merit and the true predictive value of either for successfully completing phase 3 studies or changing practice has yet to be determined, there are as yet a paucity of examples in which uniformly negative data in preclinical models have proven to be robustly positive in clinical studies. However, it is also true that well-designed phase 1 and 2 clinical trials are fundamentally important in deciding whether and how to best move forward new advances in GVHD prevention and therapy.

Cellular approaches to prevent or treat aGVHD translated from the mouse into the clinic

In contrast to pharmacologic approaches against aGVHD, that are by their nature short lived unless a state of deep tolerance is acquired during drug therapy, the transfer of a tolerogenic cell population that persists in the body could ideally lead to long-term tolerance. To exploit this concept, the transfer of tolerogenic Foxp3+ Tregs in mice was performed and led to an impressive reduction of aGVHD.40,42,100  Clinical studies using Treg transfer in the prophylactic setting was found to be connected to low aGVHD rates and adequate immune reconstitution.101-103 

The administration of mogamulizumab besides reducing adult T-cell leukemia cells also induced prolonged suppression of normal Tregs.104  Consistent with a suppressive role of Tregs against GVHD in patients undergoing allo-HCT, pretransplant use of mogamulizumab induces severe aGVHD.105  This observation supports the clinical relevance of the finding in the mouse model that Tregs are potent suppressors of GVHD.

Rapamycin (sirolimus) was shown to be more potent in suppressing conventional T-cell expansion compared with Treg expansion due to differential dependence on mammalian target of rapamycin complex/Akt expanded Treg cells106  and to polarize T cells toward a Th2 cytokine profile that was protective against aGVHD in mice.107  Motivated by these and other preclinical murine studies, a phase 2 multicenter clinical trial of ex vivo expanded rapamycin-resistant donor CD4+ Th2/Th1 cells after allogeneic-matched sibling donor HCT was performed.108  The cumulative incidence probability of aGVHD was 20% and 40% at days 100 and 180 post–allo-HCT indicating a potential benefit of this strategy that will have to be compared with other immunosuppressive interventions in future studies. Another cell population that holds promise to protect from aGVHD are MSCs, based on findings in a humanized mouse model of T-cell activation.109  However, the mouse data are controversial and differ between groups, which was also the case for the later studies in humans, as MSCs reduced aGVHD in some trials and a randomized trial failed to show a benefit against aGVHD for patients undergoing allo-HCT.110,111  The reported controversies could be due to the differences in the preparation process of the MSCs, as well as the time point of transfer.

Pharmacologic prophylaxis and therapy of cGVHD translated from the mouse into the clinic

In a mouse model of cGVHD, it was shown that animals lacking Bruton tyrosine kinase (BTK) in B cells or IL-2 inducible kinase in T cells did not develop cGVHD, indicating that these molecules play a central role in the pathophysiology of cGVHD.134  In addition to the findings in the cGVHD mouse model, activation of T and B cells from patients with active cGVHD was inhibited by BTK and IL-2 inducible kinase blockade by ibrutinib.134  Based on these data, a multicenter open-label phase 1b/2 study of ibrutinib in GVHD is being performed.112  Based on a potent inhibitor effect of ruxolitinib in an aGVHD mouse model,83  patients with cGVHD having failed multiple previous therapies were treated with the JAK1/2 inhibitor and yielded a response rate of more than 80%85 ; however, these results need to be confirmed in a prospective trial. Studies in mice showed that IL-2 is critical for Treg expansion, activity, and survival during GVHD,41  which was later followed by a phase 1/2 study showing that exogenous IL-2 increases Treg numbers and improves disease in patients with cGVHD.114  A central role for B cells in the pathogenesis of cGVHD was shown by studies in a mouse model of non-sclerodermatous cGVHD,115  which motivated the successful use of the B-cell–depleting antibody rituximab in patients with cGVHD.116,117  Posttransplant CP applied as described above was shown to reduce rates of cGVHD. Additionally, the synthetic retinoid tamibarotene (AM80G) was found to reduce skin scores and pathology of cGVHD in a mouse model,118  and has been tested consecutively in a phase 2 trial for cGVHD (#UMIN 000020363) in Japan. The multiple approaches developed from the mouse model into a clinical application for cGVHD are summarized in Figure 2 and the summary of translation of each approach is provided in Tables 3 and 4.

Figure 2

cGVHD. Simplified sketch showing the mode of action of multiple immunosuppressive strategies that were all developed from animal models into a clinical application for cGVHD. BCR, B-cell receptor; M, M phase; S, S phase; SYK, spleen tyrosine kinase.

Figure 2

cGVHD. Simplified sketch showing the mode of action of multiple immunosuppressive strategies that were all developed from animal models into a clinical application for cGVHD. BCR, B-cell receptor; M, M phase; S, S phase; SYK, spleen tyrosine kinase.

Table 3

Translation of immunosuppressive strategies from animal models of cGVHD into clinical trials

Main conclusion from the mouse model of cGVHD Reference Clinical trial Reference 
BTK inhibition reduces cGVHD in mice (2014) 134  BTK inhibition reduces cGVHD in patients (2016). Phase 1b/2 study 112  
IL-2 is critical for Treg expansion, activity, and survival during GVHD (2004, 2006) 41,131  Exogenous IL-2 increases Treg numbers and improves disease in patients with cGVHD (2011). Phase 1/2 study 114  
B cells play a central role in the pathogenesis of cGVHD (2006) 115  The B-cell–depleting antibody rituximab is effective in patients with cGVHD. Retrospective analysis (2003); phase 1/2 study (2006) 116,117  
JAK1/2 inhibition reduces cGVHD in the mouse (2015, Supplemental Figures) 85  JAK1/2 inhibition reduces cGVHD in patients refractory to multiple therapies (2015). Retrospective analysis 85  
Syk inhibition reduces cGVHD in the mouse (2014, 2015) 124,125,132  Open clinical trials for Syk inhibitors (fostamatinib, entospletinib) (2016) 135  
Main conclusion from the mouse model of cGVHD Reference Clinical trial Reference 
BTK inhibition reduces cGVHD in mice (2014) 134  BTK inhibition reduces cGVHD in patients (2016). Phase 1b/2 study 112  
IL-2 is critical for Treg expansion, activity, and survival during GVHD (2004, 2006) 41,131  Exogenous IL-2 increases Treg numbers and improves disease in patients with cGVHD (2011). Phase 1/2 study 114  
B cells play a central role in the pathogenesis of cGVHD (2006) 115  The B-cell–depleting antibody rituximab is effective in patients with cGVHD. Retrospective analysis (2003); phase 1/2 study (2006) 116,117  
JAK1/2 inhibition reduces cGVHD in the mouse (2015, Supplemental Figures) 85  JAK1/2 inhibition reduces cGVHD in patients refractory to multiple therapies (2015). Retrospective analysis 85  
Syk inhibition reduces cGVHD in the mouse (2014, 2015) 124,125,132  Open clinical trials for Syk inhibitors (fostamatinib, entospletinib) (2016) 135  
Table 4

Translation of cellular therapies from cGVHD mouse models into clinical trials

Main conclusion from the mouse model of GVHD Reference Clinical trial Reference 
Treg transfer reduces cGVHD in mice (2007) 133  Treg transfer in human cGVHD (2015). Open label trial 119  
Main conclusion from the mouse model of GVHD Reference Clinical trial Reference 
Treg transfer reduces cGVHD in mice (2007) 133  Treg transfer in human cGVHD (2015). Open label trial 119  

Cellular therapy approaches against cGVHD

Because Tregs were shown to reduce aGVHD in the mouse model,40,42,100  investigators used human donor Tregs that were cultivated for 7 to 12 days and then given to patients with cGVHD.118  Two of 5 patients showed a clinical response with improvement of cGVHD symptoms and 3 patients showed stable cGVHD symptoms for up to 21 months.119 

Trials are in progress and planned to extend these studies, and to incorporate low-dose IL-2 to treat cGVHD resistant to conventional therapies.

Novel promising targets and approaches

In order to generate hypotheses that match the human situation as closely as possible, recent studies on novel targets for GVHD, the RNA expression profiles of CD3+ T cells from NHP with aGVHD were analyzed.20  The study included cohorts of allo-HCT as an untreated control and recipients were given autologous HCT or allo-HCT with no immunoprophylaxis, sirolimus monotherapy, or tacrolimus-MTX.20  The authors found that aurora kinase A was more abundant in the GVHD group, and then directly applied this knowledge in the mouse model of GVHD where they could show that pharmacologic inhibition of aurora kinase A reduced GVHD severity. One strength of this study lies in the fact that the NHP used were evolutionary closer to resembling humans and therefore, the identified targets will most likely match the human situation much better than targets found in mice developing GVHD. Another potent strategy of GVHD prevention is the common γ-chain blockade,120  as this chain is a subunit of the receptors for IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21. However, although GVHD is reduced, the effect on T cells that reject allogeneic leukemia cells needs to be considered, making this approach most interesting for patients undergoing allo-HCT for nonmalignant diseases. Other lines of promising future translation for aGVHD are: besides others, natural killer T-cell therapy,121  IL-22 proteins that help to protect the intestinal stem cell mice,122  and modifications of the microbiome.123  cGVHD promising approaches include among others: Syk inhibitors that were shown to reduce disease severity in the mouse model124,125  and are currently developed into a clinical trial, BTK inhibition, targeting of IL-21, and B-cell activating factor that may help to control this major complication after allo-HCT.

Conclusion

It is unlikely that the mouse model will ever fully reflect the human situation even if chemotherapy based conditioning, minor antigen mismatch models, and granulocyte colony-stimulating factor mobilized peripheral blood stem cells will be used in humanized mouse models, because the situation in humans is much more complex, in particular with respect to genetic differences that lie outside the MHC loci and environmental conditions. Additionally, a major reason why certain novel pharmacologic approaches against GVHD that were shown to be successful in the mouse model then failed in the clinical setting is that they were applied to patients as treatment of steroid-refractory GVHD, which shares some similarities with severe murine GVHD but is per se a different disease. Moreover, generally, mouse models use BM that contains few T cells and are supplemented typically by splenocytes or purified T cells from secondary lymphoid organs. In contrast, patients will receive BM grafts that are “contaminated” with peripheral blood T cells, mobilized peripheral blood grafts, or cord blood grafts. T cells in each instance may have distinct functional characteristics compared with mouse T cells situated in secondary lymphoid organs. Therefore, it may be advisable to directly search for correlates in patient samples when a finding in the mouse model of GVHD has been made. This can be done by a prospective quantification of the potential target (eg, a cytokine or a kinase such as BTK) in human material, and a correlation with the incidence and severity of GVHD. Conversely, the novel “omics”-driven approaches (eg, proteomics, genomics) applied to human samples that are now increasingly used in many areas of medicine will still need a counterpart to functionally address the role of the identified candidate molecules before a translation into the clinic is possible. Additionally, there is now increasing use of “omics”-based discovery approaches in animal models that may provide new mechanisms and insights for interrogation and potential validation in GVHD patients. There are multiple examples for proteomics- or genomics-based approaches in mice driving human studies.20,21,126  Finally, another important aspect to potentially improve the predictive value of preclinical GVHD models may be to incorporate GVHD treatment models into testing rather than GVHD prevention models alone, because GVHD treatment has been and continues to be an important research field in the future, in particular with the high medical need for GVHD patients who have failed conventional therapies such as steroids. By combining insights from small and large animal models, as well as human clinical laboratory and interventional studies, we believe that this collective approach will have the highest likelihood for success in improving the outcome for patients who are in need of new therapies.

Acknowledgments

This study was supported by a grant from the Deutsche Forschungsgemeinschaft Germany (DFG); Heisenberg professorship to R.Z. (DFG ZE 872/3-1); a DFG individual grant to R.Z. (DFG ZE 872/1-2); a European Research Council consolidator grant to R.Z. (681012 GVHDCure); grants from the National Institutes of Health, National Heart, Lung and Blood Institute (R01 HL56067, HL11879), National Institute of Allergy and Infectious Diseases (AI 34495 and AI 056299), and National Cancer Institute (P01 CA142106); and a Leukemia and Lymphoma Translational Research grant (6458). The authors apologize to those investigators whose work could not be cited due to space restrictions.

Authorship

Contribution: Both R.Z. and B.R.B. collected literature, discussed the studies, and contributed equally to the writing of the manuscript.

Conflict-of-interest disclosure: The authors declare no competing financial interests.

Correspondence: Robert Zeiser, Department of Hematology and Oncology, Freiburg University Medical Center, Albert-Ludwigs University, Hugstetter Strasse 55, 79106 Freiburg, Germany; e-mail: robert.zeiser@uniklinik-freiburg.de; and Bruce R. Blazar, Department of Pediatrics, Division of Blood and Marrow Transplantation, MMC 366, 420 Delaware St SE, Minneapolis, MN 55455; e-mail: blaza001@umn.edu.

References

References
1
Jacobsohn
DA
Vogelsang
GB
Acute graft versus host disease.
Orphanet J Rare Dis
2007
, vol. 
2
 (pg. 
35
-
44
)
2
MacMillan
ML
DeFor
TE
Weisdorf
DJ
The best endpoint for acute GVHD treatment trials.
Blood
2010
, vol. 
115
 
26
(pg. 
5412
-
5417
)
3
Westin
JR
Saliba
RM
De Lima
M
, et al. 
Steroid-refractory acute GVHD: predictors and outcomes.
Adv Hematol
2011
, vol. 
2011
 pg. 
601953
 
4
Martin
PJ
Rizzo
JD
Wingard
JR
, et al. 
First- and second-line systemic treatment of acute graft-versus-host disease: recommendations of the American Society of Blood and Marrow Transplantation.
Biol Blood Marrow Transplant
2012
, vol. 
18
 
8
(pg. 
1150
-
1163
)
5
Socié
G
Ritz
J
Current issues in chronic graft-versus-host disease.
Blood
2014
, vol. 
124
 
3
(pg. 
374
-
384
)
6
Ferrara
JL
Levine
JE
Reddy
P
Holler
E
Graft-versus-host disease.
Lancet
2009
, vol. 
373
 
9674
(pg. 
1550
-
1561
)
7
Shlomchik
WD
Graft-versus-host disease.
Nat Rev Immunol
2007
, vol. 
7
 
5
(pg. 
340
-
352
)
8
Alpdogan
O
van den Brink
MR
Immune tolerance and transplantation.
Semin Oncol
2012
, vol. 
39
 
6
(pg. 
629
-
642
)
9
Socié
G
Blazar
BR
Acute graft-versus-host disease: from the bench to the bedside.
Blood
2009
, vol. 
114
 
20
(pg. 
4327
-
4336
)
10
Blazar
BR
Murphy
WJ
Abedi
M
Advances in graft-versus-host disease biology and therapy.
Nat Rev Immunol
2012
, vol. 
12
 
6
(pg. 
443
-
458
)
11
Deeg
HJ
Storb
R
Weiden
PL
, et al. 
Cyclosporin A and methotrexate in canine marrow transplantation: engraftment, graft-versus-host disease, and induction of intolerance.
Transplantation
1982
, vol. 
34
 
1
(pg. 
30
-
35
)
12
Storb
R
Deeg
HJ
Whitehead
J
, et al. 
Methotrexate and cyclosporine compared with cyclosporine alone for prophylaxis of acute graft versus host disease after marrow transplantation for leukemia.
N Engl J Med
1986
, vol. 
314
 
12
(pg. 
729
-
735
)
13
Nash
RA
Antin
JH
Karanes
C
, et al. 
Phase 3 study comparing methotrexate and tacrolimus with methotrexate and cyclosporine for prophylaxis of acute graft-versus-host disease after marrow transplantation from unrelated donors.
Blood
2000
, vol. 
96
 
6
(pg. 
2062
-
2068
)
14
Kolb
HJ
Rieder
I
Rodt
H
, et al. 
Antilymphocytic antibodies and marrow transplantation. VI. Graft-versus-host tolerance in DLA-incompatible dogs after in vitro treatment of bone marrow with absorbed antithymocyte globulin.
Transplantation
1979
, vol. 
27
 
4
(pg. 
242
-
245
)
15
Finke
J
Bethge
WA
Schmoor
C
, et al. 
ATG-Fresenius Trial Group
Standard graft-versus-host disease prophylaxis with or without anti-T-cell globulin in haematopoietic cell transplantation from matched unrelated donors: a randomised, open-label, multicentre phase 3 trial.
Lancet Oncol
2009
, vol. 
10
 
9
(pg. 
855
-
864
)
16
Kröger
N
Solano
C
Wolschke
C
, et al. 
Antilymphocyte globulin for prevention of chronic graft-versus-host disease.
N Engl J Med
2016
, vol. 
374
 
1
(pg. 
43
-
53
)
17
Huang
W
Zhao
X
Tian
Y
, et al. 
Outcomes of peripheral blood stem cell transplantation patients from HLA-mismatched unrelated donor with antithymocyte globulin (ATG)-thymoglobulin versus ATG-fresenius: a single-center study.
Med Oncol
2015
, vol. 
32
 
2
(pg. 
465
-
473
)
18
Taylor
PA
Kelly
RM
Bade
ND
Smith
MJ
Stefanski
HE
Blazar
BR
FTY720 markedly increases alloengraftment but does not eliminate host anti-donor T cells that cause graft rejection on its withdrawal.
Biol Blood Marrow Transplant
2012
, vol. 
18
 
9
(pg. 
1341
-
1352
)
19
Mielcarek
M
Storer
BE
Boeckh
M
, et al. 
Initial therapy of acute graft-versus-host disease with low-dose prednisone does not compromise patient outcomes.
Blood
2009
, vol. 
113
 
13
(pg. 
2888
-
2894
)
20
Furlan
SN
Watkins
B
Tkachev
V
, et al. 
Transcriptome analysis of GVHD reveals aurora kinase A as a targetable pathway for disease prevention.
Sci Transl Med
2015
, vol. 
7
 
315
pg. 
315ra191
 
21
You-Ten
KE
Seemayer
TA
Wisse
B
Bertley
FM
Lapp
WS
Induction of a glucocorticoid-sensitive F1-anti-parental mechanism that affects engraftment during graft-versus-host disease.
J Immunol
1995
, vol. 
155
 (pg. 
172
-
180
)
22
Hill
GR
Cooke
KR
Teshima
T
, et al. 
Interleukin-11 promotes T cell polarization and prevents acute graft-versus-host disease after allogeneic bone marrow transplantation.
J Clin Invest
1998
, vol. 
102
 
1
(pg. 
115
-
123
)
23
Teshima
T
Hill
GR
Pan
L
, et al. 
IL-11 separates graft-versus-leukemia effects from graft-versus-host disease after bone marrow transplantation.
J Clin Invest
1999
, vol. 
104
 
3
(pg. 
317
-
325
)
24
McCarthy
PL
Jr
Abhyankar
S
Neben
S
, et al. 
Inhibition of interleukin-1 by an interleukin-1 receptor antagonist prevents graft-versus-host disease.
Blood
1991
, vol. 
78
 
8
(pg. 
1915
-
1918
)
25
Hill
GR
Teshima
T
Gerbitz
A
, et al. 
Differential roles of IL-1 and TNF-alpha on graft-versus-host disease and graft versus leukemia.
J Clin Invest
1999
, vol. 
104
 
4
(pg. 
459
-
467
)
26
Schmaltz
C
Alpdogan
O
Muriglan
SJ
, et al. 
Donor T cell-derived TNF is required for graft-versus-host disease and graft-versus-tumor activity after bone marrow transplantation.
Blood
2003
, vol. 
101
 
6
(pg. 
2440
-
2445
)
27
Chen
X
Das
R
Komorowski
R
, et al. 
Blockade of interleukin-6 signaling augments regulatory T-cell reconstitution and attenuates the severity of graft-versus-host disease.
Blood
2009
, vol. 
114
 
4
(pg. 
891
-
900
)
28
Tawara
I
Koyama
M
Liu
C
, et al. 
Interleukin-6 modulates graft-versus-host responses after experimental allogeneic bone marrow transplantation.
Clin Cancer Res
2011
, vol. 
17
 
1
(pg. 
77
-
88
)
29
Antin
JH
Lee
SJ
Neuberg
D
, et al. 
A phase I/II double-blind, placebo-controlled study of recombinant human interleukin-11 for mucositis and acute GVHD prevention in allogeneic stem cell transplantation.
Bone Marrow Transplant
2002
, vol. 
29
 
5
(pg. 
373
-
377
)
30
Coccia
M
Harrison
OJ
Schiering
C
, et al. 
IL-1β mediates chronic intestinal inflammation by promoting the accumulation of IL-17A secreting innate lymphoid cells and CD4(+) Th17 cells.
J Exp Med
2012
, vol. 
209
 
9
(pg. 
1595
-
1609
)
31
Jankovic
D
Ganesan
J
Bscheider
M
, et al. 
The Nlrp3 inflammasome regulates acute graft-versus-host disease.
J Exp Med
2013
, vol. 
210
 
10
(pg. 
1899
-
1910
)
32
Chen
S
Smith
BA
Iype
J
, et al. 
MicroRNA-155-deficient dendritic cells cause less severe GVHD through reduced migration and defective inflammasome activation.
Blood
2015
, vol. 
126
 
1
(pg. 
103
-
112
)
33
Koehn
BH
Apostolova
P
Haverkamp
JM
, et al. 
GVHD-associated, inflammasome-mediated loss of function in adoptively transferred myeloid-derived suppressor cells.
Blood
2015
, vol. 
126
 
13
(pg. 
1621
-
1628
)
34
Vallera
DA
Taylor
PA
Vannice
JL
Panoskaltsis-Mortari
A
Blazar
BR
Interleukin-1 or tumor necrosis factor-alpha antagonists do not inhibit graft-versus-host disease induced across the major histocompatibility barrier in mice.
Transplantation
1995
, vol. 
60
 
11
(pg. 
1371
-
1374
)
35
McCarthy
PL
Jr
Williams
L
Harris-Bacile
M
, et al. 
A clinical phase I/II study of recombinant human interleukin-1 receptor in glucocorticoid-resistant graft-versus-host disease.
Transplantation
1996
, vol. 
62
 
5
(pg. 
626
-
631
)
36
Antin
JH
Weisdorf
D
Neuberg
D
, et al. 
Interleukin-1 blockade does not prevent acute graft-versus-host disease: results of a randomized, double-blind, placebo-controlled trial of interleukin-1 receptor antagonist in allogeneic bone marrow transplantation.
Blood
2002
, vol. 
100
 
10
(pg. 
3479
-
3482
)
37
Nestel
FP
Price
KS
Seemayer
TA
Lapp
WS
Macrophage priming and lipopolysaccharide-triggered release of tumor necrosis factor alpha during graft-versus-host disease.
J Exp Med
1992
, vol. 
175
 
2
(pg. 
405
-
413
)
38
Stickel
N
Prinz
G
Pfeifer
D
, et al. 
MiR-146a regulates the TRAF6/TNF-axis in donor T cells during GVHD.
Blood
2014
, vol. 
124
 
16
(pg. 
2586
-
2595
)
39
Valencia
X
Stephens
G
Goldbach-Mansky
R
Wilson
M
Shevach
EM
Lipsky
PE
TNF downmodulates the function of human CD4+CD25hi T-regulatory cells.
Blood
2006
, vol. 
108
 
1
(pg. 
253
-
261
)
40
Edinger
M
Hoffmann
P
Ermann
J
, et al. 
CD4+CD25+ regulatory T cells preserve graft-versus-tumor activity while inhibiting graft-versus-host disease after bone marrow transplantation.
Nat Med
2003
, vol. 
9
 
9
(pg. 
1144
-
1150
)
41
Zeiser
R
Nguyen
VH
Beilhack
A
, et al. 
Inhibition of CD4+CD25+ regulatory T-cell function by calcineurin-dependent interleukin-2 production.
Blood
2006
, vol. 
108
 
1
(pg. 
390
-
399
)
42
Taylor
PA
Lees
CJ
Blazar
BR
The infusion of ex vivo activated and expanded CD4(+)CD25(+) immune regulatory cells inhibits graft-versus-host disease lethality.
Blood
2002
, vol. 
99
 
10
(pg. 
3493
-
3499
)
43
van Groningen
LF
Liefferink
AM
de Haan
AF
, et al. 
Combination therapy with inolimomab and etanercept for severe steroid-refractory acute graft-versus-host disease.
Biol Blood Marrow Transplant
2016
, vol. 
22
 
1
(pg. 
179
-
182
)
44
Couriel
DR
Saliba
R
de Lima
M
, et al. 
A phase III study of infliximab and corticosteroids for the initial treatment of acute graft-versus-host disease.
Biol Blood Marrow Transplant
2009
, vol. 
15
 
12
(pg. 
1555
-
1562
)
45
Hahn
J
Erdmann
A
Grube
M
, et al. 
High incidence of invasive aspergillosis after treatment of acute GvHD with the combination of OKT3 and infliximab [abstract].
Bone Marrow Transplant
2001
, vol. 
27
 (pg. 
203
-
208
)
46
Veeraputhiran
M
Mangan
K
Sudden loss of the GVL effect following use of the TNF inhibitor infliximab in a chronic myelogenous leukemia patient with chronic GVHD.
Bone Marrow Transplant
2010
, vol. 
45
 
6
(pg. 
1113
-
1114
)
47
Kennedy
GA
Varelias
A
Vuckovic
S
, et al. 
Addition of interleukin-6 inhibition with tocilizumab to standard graft-versus-host disease prophylaxis after allogeneic stem-cell transplantation: a phase 1/2 trial.
Lancet Oncol
2014
, vol. 
15
 
13
(pg. 
1451
-
1459
)
48
Murai
M
Yoneyama
H
Harada
A
, et al. 
Active participation of CCR5(+)CD8(+) T lymphocytes in the pathogenesis of liver injury in graft-versus-host disease.
J Clin Invest
1999
, vol. 
104
 
1
(pg. 
49
-
57
)
49
Murai
M
Yoneyama
H
Ezaki
T
, et al. 
Peyer’s patch is the essential site in initiating murine acute and lethal graft-versus-host reaction.
Nat Immunol
2003
, vol. 
4
 
2
(pg. 
154
-
160
)
50
Wysocki
CA
Burkett
SB
Panoskaltsis-Mortari
A
, et al. 
Differential roles for CCR5 expression on donor T cells during graft-versus-host disease based on pretransplant conditioning.
J Immunol
2004
, vol. 
173
 
2
(pg. 
845
-
854
)
51
National Institutes of Health
A phase 1/2a, open-label, multicenter, dose-escalation study to evaluate the safety and tolerability of intravenous administration of RGI-2001 in patients undergoing allogeneic hematopoietic stem cell transplantation (AHSCT).
 
Available at: https://clinicaltrials.gov/show/NCT01379209. Accessed March 10, 2016
52
Hammond
WA
Heckman
M
Finn
L
, et al. 
No evidence of impact of maraviroc on outcome after allogeneic hematopoietic stem cell transplant with reduced intensity conditioning (RIC).
Biol Blood Marrow Transplant
2016
, vol. 
22
 
3
(pg. 
S396
-
S397
)
53
Hashimoto
D
Asakura
S
Matsuoka
K
, et al. 
FTY720 enhances the activation-induced apoptosis of donor T cells and modulates graft-versus-host disease.
Eur J Immunol
2007
, vol. 
37
 
1
(pg. 
271
-
281
)
54
Kim
YM
Sachs
T
Asavaroengchai
W
Bronson
R
Sykes
M
Graft-versus-host disease can be separated from graft-versus-lymphoma effects by control of lymphocyte trafficking with FTY720.
J Clin Invest
2003
, vol. 
111
 
5
(pg. 
659
-
669
)
55
Taylor
PA
Ehrhardt
MJ
Lees
CJ
, et al. 
Insights into the mechanism of FTY720 and compatibility with regulatory T cells for the inhibition of graft-versus-host disease (GVHD).
Blood
2007
, vol. 
110
 
9
(pg. 
3480
-
3488
)
56
Potì
F
Gualtieri
F
Sacchi
S
, et al. 
KRP-203, sphingosine 1-phosphate receptor type 1 agonist, ameliorates atherosclerosis in LDL-R-/- mice.
Arterioscler Thromb Vasc Biol
2013
, vol. 
33
 
7
(pg. 
1505
-
1512
)
57
National Institutes of Health
A two-part study to evaluate the safety, tolerability, pharmacokinetics, and efficacy of KRP203 in patients undergoing stem cell transplant for hematological malignancies.
 
Available at: https://clinicaltrials.gov/ct2/show/NCT01830010. Accessed March 10, 2016
58
Blazar
BR
Taylor
PA
Linsley
PS
Vallera
DA
In vivo blockade of CD28/CTLA4: B7/BB1 interaction with CTLA4-Ig reduces lethal murine graft-versus-host disease across the major histocompatibility complex barrier in mice.
Blood
1994
, vol. 
83
 
12
(pg. 
3815
-
3825
)
59
Koura
DT
Horan
JT
Langston
AA
, et al. 
In vivo T cell costimulation blockade with abatacept for acute graft-versus-host disease prevention: a first-in-disease trial.
Biol Blood Marrow Transplant
2013
, vol. 
19
 
11
(pg. 
1638
-
1649
)
60
Bashey
A
Medina
B
Corringham
S
, et al. 
CTLA4 blockade with ipilimumab to treat relapse of malignancy after allogeneic hematopoietic cell transplantation.
Blood
2009
, vol. 
113
 
7
(pg. 
1581
-
1588
)
61
Asakura
S
Hashimoto
D
Takashima
S
, et al. 
Alloantigen expression on non-hematopoietic cells reduces graft-versus-leukemia effects in mice.
J Clin Invest
2010
, vol. 
120
 
7
(pg. 
2370
-
2378
)
62
Michonneau
D
Sagoo
P
Breart
B
Garcia
Z
Celli
S
Bousso
P
The PD-1 axis enforces an anatomical segregation of CTL activity that creates tumor niches after allogeneic hematopoietic stem cell transplantation.
Immunity
2016
, vol. 
44
 
1
(pg. 
143
-
154
)
63
Panoskaltsis-Mortari
A
Lacey
DL
Vallera
DA
Blazar
BR
Keratinocyte growth factor administered before conditioning ameliorates graft-versus-host disease after allogeneic bone marrow transplantation in mice.
Blood
1998
, vol. 
92
 
10
(pg. 
3960
-
3967
)
64
Krijanovski
OI
Hill
GR
Cooke
KR
, et al. 
Keratinocyte growth factor separates graft-versus-leukemia effects from graft-versus-host disease.
Blood
1999
, vol. 
94
 
2
(pg. 
825
-
831
)
65
Jagasia
MH
Abonour
R
Long
GD
, et al. 
Palifermin for the reduction of acute GVHD: a randomized, double-blind, placebo-controlled trial.
Bone Marrow Transplant
2012
, vol. 
47
 
10
(pg. 
1350
-
1355
)
66
Goldberg
JD
Zheng
J
Castro-Malaspina
H
, et al. 
Palifermin is efficacious in recipients of TBI-based but not chemotherapy-based allogeneic hematopoietic stem cell transplants.
Bone Marrow Transplant
2013
, vol. 
48
 
1
(pg. 
99
-
104
)
67
Takashima
S
Kadowaki
M
Aoyama
K
, et al. 
The Wnt agonist R-spondin1 regulates systemic graft-versus-host disease by protecting intestinal stem cells.
J Exp Med
2011
, vol. 
208
 
2
(pg. 
285
-
294
)
68
Anderson
BE
McNiff
J
Yan
J
, et al. 
Memory CD4+ T cells do not induce graft-versus-host disease.
J Clin Invest
2003
, vol. 
112
 
1
(pg. 
101
-
108
)
69
Chen
BJ
Deoliveira
D
Cui
X
, et al. 
Inability of memory T cells to induce graft-versus-host disease is a result of an abortive alloresponse.
Blood
2007
, vol. 
109
 
7
(pg. 
3115
-
3123
)
70
Bleakley
M
Heimfeld
S
Loeb
KR
, et al. 
Outcomes of acute leukemia patients transplanted with naive T cell-depleted stem cell grafts.
J Clin Invest
2015
, vol. 
125
 
7
(pg. 
2677
-
2689
)
71
Ullrich
SE
Photoinactivation of T-cell function with psoralen and UVA radiation suppresses the induction of experimental murine graft-versus-host disease across major histocompatibility barriers.
J Invest Dermatol
1991
, vol. 
96
 
3
(pg. 
303
-
308
)
72
Zhang
H
Chen
R
Cheng
J
Jin
N
Chen
B
Systematic review and meta-analysis of prospective studies for ECP treatment in patients with steroid-refractory acute GVHD.
Patient Prefer Adherence
2015
, vol. 
9
 (pg. 
105
-
111
)
73
Greinix
HT
Volc-Platzer
B
Kalhs
P
, et al. 
Extracorporeal photochemotherapy in the treatment of severe steroid-refractory acute graft-versus-host disease: a pilot study.
Blood
2000
, vol. 
96
 
7
(pg. 
2426
-
2431
)
74
Hechinger
AK
Maas
K
Dürr
C
, et al. 
Inhibition of protein geranylgeranylation and farnesylation protects against graft-versus-host disease via effects on CD4 effector T cells.
Haematologica
2013
, vol. 
98
 
1
(pg. 
31
-
40
)
75
Zeiser
R
Youssef
S
Baker
J
Kambhan
N
Steinman
L
Negrin
RS
Preemptive HMG-CoA reductase inhibition provides graft-versus-host disease protection by Th-2 polarization while sparing graft-versus-leukemia activity.
Blood
2007
, vol. 
110
 
13
(pg. 
4588
-
4598
)
76
Wang
Y
Li
D
Jones
D
, et al. 
Blocking LFA-1 activation with lovastatin prevents graft-versus-host disease in mouse bone marrow transplantation.
Biol Blood Marrow Transplant
2009
, vol. 
15
 
12
(pg. 
1513
-
1522
)
77
Rotta
M
Storer
BE
Storb
RF
, et al. 
Donor statin treatment protects against severe acute graft-versus-host disease after related allogeneic hematopoietic cell transplantation.
Blood
2010
, vol. 
115
 
6
(pg. 
1288
-
1295
)
78
Rotta
M
Storer
BE
Storb
R
, et al. 
Impact of recipient statin treatment on graft-versus-host disease after allogeneic hematopoietic cell transplantation.
Biol Blood Marrow Transplant
2010
, vol. 
16
 
10
(pg. 
1463
-
1466
)
79
Hamadani
M
Gibson
LF
Remick
SC
, et al. 
Sibling donor and recipient immune modulation with atorvastatin for the prophylaxis of acute graft-versus-host disease.
J Clin Oncol
2013
, vol. 
31
 
35
(pg. 
4416
-
4423
)
80
Efebera
YA
Geyer
S
Andritsos
L
, et al. 
Atorvastatin for the prophylaxis of acute graft-versus-host disease in patients undergoing HLA-matched related donor allogeneic hematopoietic stem cell transplantation (allo-HCT).
Biol Blood Marrow Transplant
2016
, vol. 
22
 
1
(pg. 
71
-
79
)
81
Reddy
P
Sun
Y
Toubai
T
, et al. 
Histone deacetylase inhibition modulates indoleamine 2,3-dioxygenase-dependent DC functions and regulates experimental graft-versus-host disease in mice.
J Clin Invest
2008
, vol. 
118
 
7
(pg. 
2562
-
2573
)
82
Choi
SW
Braun
T
Chang
L
, et al. 
Vorinostat plus tacrolimus and mycophenolate to prevent graft-versus-host disease after related-donor reduced-intensity conditioning allogeneic haemopoietic stem-cell transplantation: a phase 1/2 trial.
Lancet Oncol
2014
, vol. 
15
 
1
(pg. 
87
-
95
)
83
Spoerl
S
Mathew
NR
Bscheider
M
, et al. 
Activity of therapeutic JAK 1/2 blockade in graft-versus-host disease.
Blood
2014
, vol. 
123
 
24
(pg. 
3832
-
3842
)
84
Carniti
C
Gimondi
S
Vendramin
A
, et al. 
Pharmacologic inhibition of JAK1/JAK2 signaling reduces experimental murine acute GVHD while preserving GVT effects.
Clin Cancer Res
2015
, vol. 
21
 
16
(pg. 
3740
-
3749
)
85
Zeiser
R
Burchert
A
Lengerke
C
, et al. 
Ruxolitinib in corticosteroid-refractory graftversus-host disease after allogeneic stem cell transplantation: a multicenter survey.
Leukemia
2015
, vol. 
29
 
10
(pg. 
2062
-
2068
)
86
Takahashi
S
Hashimoto
D
Hayase
E
Teshima
T
Topical ruxolitinib protects LGR5+ stem cells in the hair follicle and ameliorates skin graft-versus-host disease.
Biol Blood Marrow Transplant
2016
, vol. 
22
 
3
(pg. 
S21
-
S22
)
87
Sun
K
Welniak
LA
Panoskaltsis-Mortari
A
, et al. 
Inhibition of acute graft-versus-host disease with retention of graft-versus-tumor effects by the proteasome inhibitor bortezomib [published correction appears in Proc Natl Acad Sci USA. 2004;101(34):12777].
Proc Natl Acad Sci USA
2004
, vol. 
101
 
21
(pg. 
8120
-
8125
)
88
Koreth
J
Stevenson
KE
Kim
HT
, et al. 
Bortezomib, tacrolimus, and methotrexate for prophylaxis of graft-versus-host disease after reduced-intensity conditioning allogeneic stem cell transplantation from HLA-mismatched unrelated donors.
Blood
2009
, vol. 
114
 
18
(pg. 
3956
-
3959
)
89
Koreth
J
Stevenson
KE
Kim
HT
, et al. 
Bortezomib-based graft-versus-host disease prophylaxis in HLA-mismatched unrelated donor transplantation.
J Clin Oncol
2012
, vol. 
30
 
26
(pg. 
3202
-
3208
)
90
Liu
R
La Cava
A
Bai
XF
, et al. 
Cooperation of invariant NKT cells and CD4+CD25+ T regulatory cells in the prevention of autoimmune myasthenia.
J Immunol
2005
, vol. 
175
 
12
(pg. 
7898
-
7904
)
91
Kuns
RD
Morris
ES
Macdonald
KP
, et al. 
Invariant natural killer T cell-natural killer cell interactions dictate transplantation outcome after alpha-galactosylceramide administration.
Blood
2009
, vol. 
113
 
23
(pg. 
5999
-
6010
)
92
Hashimoto
D
Asakura
S
Miyake
S
, et al. 
Stimulation of host NKT cells by synthetic glycolipid regulates acute graft-versus-host disease by inducing Th2 polarization of donor T cells.
J Immunol
2005
, vol. 
174
 
1
(pg. 
551
-
556
)
93
Mayumi
H
Good
RA
Long-lasting skin allograft tolerance in adult mice induced across fully allogeneic (multimajor H-2 plus multiminor histocompatibility) antigen barriers by a tolerance-inducing method using cyclophosphamide.
J Exp Med
1989
, vol. 
169
 
1
(pg. 
213
-
238
)
94
Eto
M
Mayumi
H
Tomita
Y
, et al. 
Specific destruction of host-reactive mature T cells of donor origin prevents graft-versus-host disease in cyclophosphamide-induced tolerant mice.
J Immunol
1991
, vol. 
146
 
5
(pg. 
1402
-
1409
)
95
Ganguly
S
Ross
DB
Panoskaltsis-Mortari
A
, et al. 
Donor CD4+ Foxp3+ regulatory T cells are necessary for posttransplantation cyclophosphamide-mediated protection against GVHD in mice.
Blood
2014
, vol. 
124
 
13
(pg. 
2131
-
2141
)
96
Kanakry
CG
Ganguly
S
Zahurak
M
, et al. 
Aldehyde dehydrogenase expression drives human regulatory T cell resistance to posttransplantation cyclophosphamide.
Sci Transl Med
2013
, vol. 
5
 
211
pg. 
211ra157
 
97
Kanakry
CG
O’Donnell
PV
Furlong
T
, et al. 
Multi-institutional study of post-transplantation cyclophosphamide as single-agent graft-versus-host disease prophylaxis after allogeneic bone marrow transplantation using myeloablative busulfan and fludarabine conditioning.
J Clin Oncol
2014
, vol. 
32
 
31
(pg. 
3497
-
3505
)
98
Luznik
L
Bolaños-Meade
J
Zahurak
M
, et al. 
High-dose cyclophosphamide as single-agent, short-course prophylaxis of graft-versus-host disease.
Blood
2010
, vol. 
115
 
16
(pg. 
3224
-
3230
)
99
Solomon
SR
Sanacore
M
Zhang
X
, et al. 
Calcineurin inhibitor--free graft-versus-host disease prophylaxis with post-transplantation cyclophosphamide and brief-course sirolimus following reduced-intensity peripheral blood stem cell transplantation.
Biol Blood Marrow Transplant
2014
, vol. 
20
 
11
(pg. 
1828
-
1834
)
100
Hoffmann
P
Ermann
J
Edinger
M
Fathman
CG
Strober
S
Donor-type CD4(+)CD25(+) regulatory T cells suppress lethal acute graft-versus-host disease after allogeneic bone marrow transplantation.
J Exp Med
2002
, vol. 
196
 
3
(pg. 
389
-
399
)
101
Di Ianni
M
Falzetti
F
Carotti
A
, et al. 
Tregs prevent GVHD and promote immune reconstitution in HLA-haploidentical transplantation.
Blood
2011
, vol. 
117
 
14
(pg. 
3921
-
3928
)
102
Brunstein
CG
Miller
JS
Cao
Q
, et al. 
Infusion of ex vivo expanded T regulatory cells in adults transplanted with umbilical cord blood: safety profile and detection kinetics.
Blood
2011
, vol. 
117
 
3
(pg. 
1061
-
1070
)
103
Brunstein
CG
Miller
JS
McKenna
DH
, et al. 
Umbilical cord blood-derived T regulatory cells to prevent GVHD: kinetics, toxicity profile, and clinical effect.
Blood
2016
, vol. 
127
 
8
(pg. 
1044
-
1051
)
104
Ishida
T
Joh
T
Uike
N
, et al. 
Defucosylated anti-CCR4 monoclonal antibody (KW-0761) for relapsed adult T-cell leukemia-lymphoma: a multicenter phase II study.
J Clin Oncol
2012
, vol. 
30
 
8
(pg. 
837
-
842
)
105
Inoue
Y
Fuji
S
Tanosaki
R
Fukuda
T
Pretransplant mogamulizumab against ATLL might increase the risk of acute GVHD and non-relapse mortality [published online ahead of print December 21, 2015].
Bone Marrow Transplant
106
Zeiser
R
Leveson-Gower
DB
Zambricki
EA
, et al. 
Differential impact of mammalian target of rapamycin inhibition on CD4+CD25+Foxp3+ regulatory T cells as compared to conventional CD4+ T cells.
Blood
2008
, vol. 
111(1)
 (pg. 
453
-
462
)
107
Foley
JE
Jung
U
Miera
A
, et al. 
Ex vivo rapamycin generates donor Th2 cells that potently inhibit graft-versus-host disease and graft-versus-tumor effects via an IL-4-dependent mechanism.
J Immunol
2005
, vol. 
175
 
9
(pg. 
5732
-
5743
)
108
Fowler
DH
Mossoba
ME
Steinberg
SM
, et al. 
Phase 2 clinical trial of rapamycin-resistant donor CD4+ Th2/Th1 (T-Rapa) cells after low-intensity allogeneic hematopoietic cell transplantation.
Blood
2013
, vol. 
121
 
15
(pg. 
2864
-
2874
)
109
Maitra
B
Szekely
E
Gjini
K
, et al. 
Human mesenchymal stem cells support unrelated donor hematopoietic stem cells and suppress T-cell activation.
Bone Marrow Transplant
2004
, vol. 
33
 
6
(pg. 
597
-
604
)
110
Kordelas
L
Rebmann
V
Ludwig
AK
, et al. 
MSC-derived exosomes: a novel tool to treat therapy-refractory graft-versus-host disease.
Leukemia
2014
, vol. 
28
 
4
(pg. 
970
-
973
)
111
Le Blanc
K
Rasmusson
I
Sundberg
B
, et al. 
Treatment of severe acute graft-versus-host disease with third party haploidentical mesenchymal stem cells.
Lancet
2004
, vol. 
363
 
9419
(pg. 
1439
-
1441
)
112
Study of the Bruton’s tyrosine kinase inhibitor in subjects with chronic graft versus host disease. ClinicalTrials.gov Identifier: NCT02195869. Available at: https://clinicaltrials.gov/ct2/show/NCT02195869. Accessed March 10, 2016.
113
Zheng
H
Matte-Martone
C
Jain
D
McNiff
J
Shlomchik
WD
Central memory CD8+ T cells induce graft-versus-host disease and mediate graft-versus-leukemia.
J Immunol
2009
, vol. 
182
 
10
(pg. 
5938
-
5948
)
114
Koreth
J
Matsuoka
K
Kim
HT
, et al. 
Interleukin-2 and regulatory T cells in graft-versus-host disease.
N Engl J Med
2011
, vol. 
365
 
22
(pg. 
2055
-
2066
)
115
Zhang
C
Todorov
I
Zhang
Z
, et al. 
Donor CD4+ T and B cells in transplants induce chronic graft-versus-host disease with autoimmune manifestations.
Blood
2006
, vol. 
107
 
7
(pg. 
2993
-
3001
)
116
Ratanatharathorn
V
Ayash
L
Reynolds
C
, et al. 
Treatment of chronic graft-versus-host disease with anti-CD20 chimeric monoclonal antibody.
Biol Blood Marrow Transplant
2003
, vol. 
9
 
8
(pg. 
505
-
511
)
117
Cutler
C
Miklos
D
Kim
HT
, et al. 
Rituximab for steroid-refractory chronic graft-versus-host disease.
Blood
2006
, vol. 
108
 
2
(pg. 
756
-
762
)
118
Nishimori
H
Maeda
Y
Teshima
T
, et al. 
Synthetic retinoid Am80 ameliorates chronic graft-versus-host disease by down-regulating Th1 and Th17.
Blood
2012
, vol. 
119
 
1
(pg. 
285
-
295
)
119
Theil
A
Tuve
S
Oelschlägel
U
, et al. 
Adoptive transfer of allogeneic regulatory T cells into patients with chronic graft-versus-host disease.
Cytotherapy
2015
, vol. 
17
 
4
(pg. 
473
-
486
)
120
Hechinger
AK
Smith
BA
Flynn
R
, et al. 
Therapeutic activity of multiple common γ-chain cytokine inhibition in acute and chronic GVHD.
Blood
2015
, vol. 
125
 
3
(pg. 
570
-
580
)
121
Schneidawind
D
Baker
J
Pierini
A
, et al. 
Third-party CD4+ invariant natural killer T cells protect from murine GVHD lethality.
Blood
2015
, vol. 
125
 
22
(pg. 
3491
-
3500
)
122
Hanash
AM
Dudakov
JA
Hua
G
, et al. 
Interleukin-22 protects intestinal stem cells from immune-mediated tissue damage and regulates sensitivity to graft versus host disease.
Immunity
2012
, vol. 
37
 
2
(pg. 
339
-
350
)
123
Jenq
RR
Ubeda
C
Taur
Y
, et al. 
Regulation of intestinal inflammation by microbiota following allogeneic bone marrow transplantation.
J Exp Med
2012
, vol. 
209
 
5
(pg. 
903
-
911
)
124
Leonhardt
F
Zirlik
K
Buchner
M
, et al. 
Spleen tyrosine kinase (Syk) is a potent target for GvHD prevention at different cellular levels.
Leukemia
2012
, vol. 
26
 
7
(pg. 
1617
-
1629
)
125
Flynn
R
Allen
JL
Luznik
L
, et al. 
Targeting Syk-activated B cells in murine and human chronic graft-versus-host disease.
Blood
2015
, vol. 
125
 
26
(pg. 
4085
-
4094
)
126
Schwab
L
Goroncy
L
Palaniyandi
S
, et al. 
Neutrophil granulocytes recruited upon translocation of intestinal bacteria enhance graft-versus-host disease via tissue damage.
Nat Med
2014
, vol. 
20
 
6
(pg. 
648
-
654
)
127
Weiden
PL
Doney
K
Storb
R
Thomas
ED
Antihuman thymocyte globulin for prophylaxis of graft-versus-host disease. A randomized trial in patients with leukemia treated with HLA-identical sibling marrow grafts.
Transplantation
1979
, vol. 
27
 
4
(pg. 
227
-
230
)
128
Rager
A
Frey
N
Goldstein
SC
, et al. 
Inflammatory cytokine inhibition with combination daclizumab and infliximab for steroid-refractory acute GVHD.
Bone Marrow Transplant
2011
, vol. 
46
 
3
(pg. 
430
-
435
)
129
Reshef
R
Luger
SM
Hexner
EO
, et al. 
Blockade of lymphocyte chemotaxis in visceral graft-versus-host disease.
N Engl J Med
2012
, vol. 
367
 
2
(pg. 
135
-
145
)
130
Gregoire-Gauthier
J
Selleri
S
Fontaine
F
, et al. 
Therapeutic efficacy of cord blood-derived mesenchymal stromal cells for the prevention of acute graft-versus-host disease in a xenogenic mouse model.
Stem Cells Dev
2012
, vol. 
21
 
10
(pg. 
1616
-
1626
)
131
Malek
TR
Bayer
AL
Tolerance, not immunity, crucially depends on IL-2.
Nat Rev Immunol
2004
, vol. 
4
 
9
(pg. 
665
-
674
)
132
Le Huu
D
Kimura
H
Date
M
, et al. 
Blockade of Syk ameliorates the development of murine sclerodermatous chronic graft-versus-host disease.
J Dermatol Sci
2014
, vol. 
74
 
3
(pg. 
214
-
221
)
133
Giorgini
A
Noble
A
Blockade of chronic graft-versus-host disease by alloantigen-induced CD4+CD25+Foxp3+ regulatory T cells in nonlymphopenic hosts.
J Leukoc Biol
2007
, vol. 
82
 
5
(pg. 
1053
-
1061
)
134
Dubovsky
JA
Flynn
R
Du
J
, et al. 
Ibrutinib treatment ameliorates murine chronic graft-versus-host disease.
J Clin Invest
2014
, vol. 
124
 (pg. 
4867
-
4876
)
135
National Institutes of Health. Evaluation of fostamatinib in patients with cGVHD after allogeneic stem cell transplant. Available at: www.clinicaltrials.gov/ct2/show/ NCT02611063. Assessed March 10, 2016.

Author notes

*

R.Z. and B.R.B. are equal contributors to this study.