A new induction protocol for the control of steroid refractory/dependent acute graft versus host disease with alefacept and tacrolimus

Hepatic graft-versus-host disease: what we know, when to biopsy, and how to diagnose

Graft-versus-host disease (GVHD) is one of the serious complications that may develop after hematopoietic cell transplantation (HCT), for hematologic malignancies, solid organ transplantation, and other hematologic disorders. GVHD develops due to T lymphocytes present in the graft attacking the host antigens, which results in tissue damage. A significant number of HCT patients develop acute or chronic GVHD, which may affect multiple organs including the liver. The diagnosis of hepatic GVHD (hGVHD) is challenging as many other conditions in HCT patients may lead to liver dysfunction. Particularly challenging among the various conditions that give rise to liver dysfunction is differentiating sinusoidal obstruction syndrome and drug-induced liver injury (DILI) from hGVHD on clinical grounds and laboratory tests. Despite the minimal risks involved in performing a liver biopsy, the information gleaned from the histopathologic changes may help in the management of these very complex patients. There is a spectrum of histologic features found in hGVHD, and most involve histopathologic changes affecting the interlobular bile ducts. These include nuclear and cytoplasmic abnormalities including dysmorphic bile ducts, apoptosis, and cholangiocyte necrosis, among others. The hepatitic form of hGVHD typically shows severe acute hepatitis. With chronic hGVHD, there is progressive bile duct loss and eventually fibrosis. Accurate diagnosis of hGVHD is paramount so that timely treatment and management can be initiated. Techniques to prevent and lower the risk of GVHD from developing have recently evolved. If a diagnosis of acute GVHD is made, the first-line of treatment is steroids. Recurrence is common and steroid resistance or dependency is not unusual in this setting. Second-line therapies differ among institutions and have not been uniformly established. The development of GVHD, particularly hGVHD, is associated with increased morbidity and mortality.

Activation and regulation of alloreactive T cell immunity in solid organ transplantation

Transplantation is the only curative treatment for patients with kidney failure but it poses unique immunological challenges that must be overcome to prevent allograft rejection and ensure long-term graft survival. Alloreactive T cells are important contributors to graft rejection, and a clearer understanding of the mechanisms by which these cells recognize donor antigens - through direct, indirect or semi-direct pathways - will facilitate their therapeutic targeting. Post-T cell priming rejection responses can also be modified by targeting pathways that regulate T cell trafficking, survival cytokines or innate immune activation. Moreover, the quantity and quality of donor-reactive memory T cells crucially shape alloimmune responses. Of note, many fundamental concepts in transplant immunology have been derived from models of infection. However, the programmed differentiation of allograft-specific T cell responses is probably distinct from that of pathogen-elicited responses, owing to the dearth of pathogen-derived innate immune activation in the transplantation setting. Understanding the fundamental (and potentially unique) immunological pathways that lead to allograft rejection is therefore a prerequisite for the rational development of therapeutics that promote transplantation tolerance.

A structural perspective on the design of decoy immune modulators

Therapeutic mAbs have dominated the class of immunotherapeutics in general and immune checkpoint inhibitors in particular. The high specificity of mAbs to the target molecule as well as their extended half-life and (or) the effector functions raised by the Fc part are some of the important aspects that contribute to the success of this class of therapeutics. Equally potential candidates are decoys and their fusions that can address some of the inherent limitations of mAbs, like immunogenicity, resistance development, low bio-availability and so on, besides maintaining the advantages of mAbs. The decoys are molecules that trap the ligands and prevent them from interacting with the signaling receptors. Although a few FDA-approved decoy immune modulators are very successful, the potential of this class of drugs is yet to be fully realized. Here, we review various strategies employed in fusion protein therapeutics with a focus on the design of decoy immunomodulators from the structural perspective and discuss how the information on protein structure and function can strategically guide the development of next-generation immune modulators.

Graft Versus Host Disease After Liver Transplantation in Adults: A Case series, Review of Literature, and an Approach to Management

BACKGROUND

Graft-versus-host-disease (GVHD) after liver transplantation (LT) is a deadly complication with very limited data on risk factors, diagnosis and management. We report a case series and a comprehensive review of the literature.

METHODS

Data were systematically extracted from reports of GVHD after LT, and from the United Network for Organ Sharing database. Group comparisons were performed.

RESULTS

One hundred fifty-six adult patients with GVHD after LT have been reported. Median time to GVHD onset was 28 days. Clinical features were skin rash (92%), pancytopenia (78%), and diarrhea (65%). Six-month mortality with GVHD after LT was 73%. Sepsis was the most common cause of death (60%). Enterobacter bacteremia, invasive aspergillosis, and disseminated Candida infections were frequently reported. Recipient age over 50 years is a risk factor for GVHD after LT. Hepatocellular carcinoma was overrepresented, whereas chronic hepatitis C was underrepresented, in reported United States GVHD cases relative to all United Network for Organ Sharing database LT cases. Mortality rate with treatment of GVHD after LT was 84% with high-dose steroids alone, 75% to 100% with regimens using dose increases of calcineurin inhibitors, and 55% with IL-2 antagonists. Mortality was 25% in small case series using the CD2-blocker alefacept or TNF-α antagonists.

CONCLUSIONS

Age older than 50 years and hepatocellular carcinoma appear to be risk factors for GVHD. Hepatitis C may be protective. High-dose steroids and calcineurin inhibitors are ineffective in the treatment of GVHD after LT. CD2-blockers and TNF-α antagonists appear promising. We propose a diagnostic algorithm to assist clinicians in managing adults with GVHD after LT.

Role of Memory T Cells in Allograft Rejection and Tolerance

Memory T cells are characterized by their low activation threshold, robust effector functions, and resistance to conventional immunosuppression and costimulation blockade. Unlike their naïve counterparts, memory T cells reside in and recirculate through peripheral non-lymphoid tissues. Alloreactive memory T cells are subdivided into different categories based on their origins, phenotypes, and functions. Recipients whose immune systems have been directly exposed to allogeneic major histocompatibility complex (MHC) molecules display high affinity alloreactive memory T cells. In the absence of any prior exposure to allogeneic MHC molecules, endogenous alloreactive memory T cells are regularly generated through microbial infections (heterologous immunity). Regardless of their origin, alloreactive memory T cells represent an essential element of the allograft rejection process and a major barrier to tolerance induction in clinical transplantation. This article describes the different subsets of alloreactive memory T cells involved in transplant rejection and examine their generation, functional properties, and mechanisms of action. In addition, we discuss strategies developed to target deleterious allospecific memory T cells in experimental animal models and clinical settings.

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.

Future prospects in immunosuppression for liver transplantation

1. Our increasing understanding of signaling pathways and cellular interactions in transplant immunobiology and the availability of novel immunosuppressive agents have facilitated targeted strategies. 2. The driving forces behind the development of new immunosuppressive regimens are the long-term complications of current immunosuppressive regimens (particularly renal dysfunction and metabolic disturbances). 3. By regulatory mandate, the requirement for the primary endpoint to be a composite of death, graft loss, and rejection remains intact; however, current and future clinical trials could incorporate key secondary endpoints that address renal and metabolic derangements.

Stem Cell Transplantation for Hematological Malignancies: Prospects for Personalized Medicine and Co-therapy with Mesenchymal Stem Cells

Bone marrow transplantation is a form of cell therapy that has been in practice for decades for the treatment of hematological disorders and solid tumors. Immunosuppressive therapy has been a mainstay for treatment, but the severity of the adverse effects has made it an undesirable choice. Mesenchymal stem cells (MSCs), which reside in the vascular regions of the bone marrow, have been shown to serve as cellular support for the hematopoietic stem cell (HSC) niche. Furthermore, the immune suppressive properties of MSCs have been explored in the treatment of inflammatory and autoimmune disorders. Thus, co-therapy with MSCs has been shown to facilitate engraftment of hematopoietic cells by suppressive graft versus host disease (GvHD). Although the mechanism by which MSCs suppress GvHD is unclear, the experimental evidence suggests that this partly occurs by modulation of immune response such as the induction of regulatory T cells. This paper discusses the role of MSCs as co-therapy for the future of stem cell transplantation, with the overarching theme of personalized medicine for cell-based health interventions.

Treatment of graft-versus-host disease with monoclonal antibodies and related fusion proteins

Allogeneic hematopoietic stem cell transplantation has evolved from an experimental treatment approach to a widely used, curative therapy to treat malignant and nonmalignant diseases of the hematopoietic system. Despite advances in donor selection, conditioning regimens and supportive care, acute and chronic graft-versus-host disease (GvHD) remain a major cause of morbidity and mortality. Steroids are the standard first-line treatment and are able to control GvHD in approximately 50% of patients. Those who fail on steroids have a poor long-term prognosis. Therefore, a large number of drugs and procedures have been evaluated as second-line therapy. Monoclonal antibodies have increasingly been used to treat malignancy and autoimmune disease during the last 20 years. Their unique ability to target specific antigens theoretically enables them to directly interfere with cellular mechanisms that are involved in GvHD pathology. For this reason, monoclonal antibodies have been studied extensively as a second-line treatment for acute and chronic GvHD. The purpose of this article is to collect published data on clinical trials from the current literature and to give an overview on efficacy and toxicity of monoclonal antibody treatment for GvHD.

Mycophenolate pharmacokinetics and association with response to acute graft-versus-host disease treatment from the Blood and Marrow Transplant Clinical Trials Network

There are limited data as to the effectiveness of mycophenolate mofetil (MMF) plus high-dose corticosteroids for the treatment of acute graft-versus-host disease (aGVHD), and even less data regarding the pharmacokinetic disposition and exposure-response relationship of MMF in individuals with GVHD. MMF pharmacokinetics were studied in a multicenter Blood and Marrow Transplant Clinical Trials Network randomized phase II trial evaluating the effectiveness of MMF as one of 4 agents added to corticosteroids as treatment of aGVHD. Thirty-two of the patients randomized to receive MMF underwent pharmacokinetic sampling in weeks 1 and 2 were studied. Mean age was 41 +/- 13.6 years. Twenty one (65.6%), 5 (15.6%), 6 (18.8%) patients had a complete response (CR), partial response (PR) or lesser response by day 28, respectively. Twenty-five (78.1%), 2 (6.3%), 5 (15.6%) patients had a CR, PR, or other response by day 56 to treatment, respectively. Mycophenolic acid (MPA) pharmacokinetic measurements from weeks 1 and 2 did not correlate with CR at either day 28 or day 56 (P > .07); however, if the mean of weeks 1 and 2 total MPA troughs was >0.5 microg/mL or that of an unbound trough was >0.015 microg/mL, then a significantly greater proportion achieved CR + PR at days 28 and 56. CR + PR at day 28 was observed in 19 of 19 patients (100%) with a mean total trough >0.5 mg/mL, but in only 7 of 13 (54%) with a mean total trough < or =0.5 microg/mL (P = .002). Similarly, CR + PR at day 28 was seen in 15 of 15 patients (100%) with an unbound trough concentration >0.015 microg/mL, but in only 11 of 17 (65%) with an unbound trough concentration < or =0.015 microg/mL (P = .02). There was no association between the pharmacokinetic measures and risk of infection by day 90 or overall survival (OS) at day 180 postrandomization. About one-half of subjects did not achieve the favorable MPA total and unbound trough concentrations. The current practice of MMF 1 gm twice daily dosing provides low plasma concentrations in many patients. Higher doses may improve the efficacy of MMF as aGVHD therapy.

Alefacept: where it stands today

IMPORTANCE OF THE FIELD

The use of biologics that target a subset of immune cells in the treatment of immune-mediated ailments is an emerging field. Alefacept is one of the first biologics in the treatment of psoriasis. It selectively reduces CD45RO(+) memory T cells and inhibits T-cell activation. Clinical data support its safety and efficacy in a substantial subset of patients with psoriasis.

AREAS COVERED IN THIS REVIEW

This article reviews the mechanism of action and the pharmacokinetic and pharmacodynamic properties of alefacept. It also presents the available data about its effectiveness, modes of treatment as well as safety and efficacy in the treatment of psoriasis and other immune-based dermatologic disorders.

WHAT THE READER WILL GAIN

An overview of the published data about the clinical and adverse effects of alefacept in the treatment of psoriasis and a myriad of immunologically-based disorders.

TAKE HOME MESSAGE

Ongoing literature supports that alefacept is a safe alternative for the treatment of psoriasis. However, it remains the least prescribed medication in this group of drugs, mainly because it is only effective in a small proportion of patients. Nonetheless, its long-lasting effects and tolerability make it an excellent choice for those who do respond.

Graft-vs-host disease after small bowel transplantation in children

PURPOSE

Graft-vs-host disease (GVHD) is a rare complication of transplantation of organs rich in immunocompetent cells. The goal of this study was to report the features of GVHD after small bowel transplantation (SBTx) in children.

METHODS

The study involved a retrospective review of patients undergoing SBTx between 1999 and 2009 who had GVHD.

RESULTS

Of 46 children receiving 52 intestinal grafts (2 liver-intestine and 3 multivisceral), 5 (10%) developed GVHD. Median age at transplant was 42 (19-204) months. Baseline immunosupression consisted of tacrolimus and steroids supplemented with thymoglobulin (n = 2) or basiliximab (n = 3) for induction. Median time between transplantation and GVHD was 47 (16-333) days. All patients had generalized rash, 2 had diarrhea, and 2 had respiratory symptoms. Other symptoms were glomerulonephritis (n = 1) and conjunctivitis (n = 1). Four developed severe hematologic disorders. The diagnosis was confirmed by skin biopsy in 4 patients and supported by chimerism studies in two. Colonoscopy and opthalmoscopic findings were also suggestive in one. Treatment consisted of steroids and decrease of tacrolimus, with partial response in four. Other immunosuppressants were used in refractory or recurrent cases. Three patients died within 4 months after diagnosis.

CONCLUSION

Graft-vs-host disease is a devastating complication of SBTx, with high mortality probably associated with severe immunologic dysregulation.

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.