Novel targeted therapies for autoimmunity

Clair EW. Solving the puzzle of autoimmunity: critical questions

Despite recent advances in delineating the pathogenic mechanisms of autoimmune disease, the puzzle that reveals the true picture of these diverse immunological disorders is yet to be solved. We know that the human leukocyte antigen (HLA) loci as well as many different genetic susceptibility loci with relatively small effect sizes predispose to various autoimmune diseases and that environmental factors are involved in triggering disease. Models for mechanisms of disease become increasingly complex as relationships between components of both the adaptive and innate immune systems are untangled at the molecular level. In this article, we pose some of the important questions about autoimmunity where the answers will advance our understanding of disease pathogenesis and improve the rational design of novel therapies. How is autoimmunity triggered, and what components of the immune response drive the clinical manifestations of disease? What determines whether a genetically predisposed individual will develop an autoimmune disease? Is restoring immune tolerance the secret to finding cures for autoimmune disease? Current research efforts seek answers to these big questions.

Restoring the balance: immunotherapeutic combinations for autoimmune disease

Autoimmunity occurs when T cells, B cells or both are inappropriately activated, resulting in damage to one or more organ systems. Normally, high-affinity self-reactive T and B cells are eliminated in the thymus and bone marrow through a process known as central immune tolerance. However, low-affinity self-reactive T and B cells escape central tolerance and enter the blood and tissues, where they are kept in check by complex and non-redundant peripheral tolerance mechanisms. Dysfunction or imbalance of the immune system can lead to autoimmunity, and thus elucidation of normal tolerance mechanisms has led to identification of therapeutic targets for treating autoimmune disease. In the past 15 years, a number of disease-modifying monoclonal antibodies and genetically engineered biologic agents targeting the immune system have been approved, notably for the treatment of rheumatoid arthritis, inflammatory bowel disease and psoriasis. Although these agents represent a major advance, effective therapy for other autoimmune conditions, such as type 1 diabetes, remain elusive and will likely require intervention aimed at multiple components of the immune system. To this end, approaches that manipulate cells ex vivo and harness their complex behaviors are being tested in preclinical and clinical settings. In addition, approved biologic agents are being examined in combination with one another and with cell-based therapies. Substantial development and regulatory hurdles must be overcome in order to successfully combine immunotherapeutic biologic agents. Nevertheless, such combinations might ultimately be necessary to control autoimmune disease manifestations and restore the tolerant state.

Orientation-specific attachment of polymeric microtubes on cell surfaces

Tubular particles presenting heterogeneous regions of chemistry on the tube-ends versus the side are fabricated and are shown to control the particle orientation on the surface of live lymphocytes. Controlling the orientation of anisotropic microparticles on cell surfaces is of interest for biomedical applications and drug delivery in particular, since it can be used to promote or resist particle internalization.

Synergistic activation of inflammatory cytokine genes by interferon-γ-induced chromatin remodeling and toll-like receptor signaling

Synergistic activation of inflammatory cytokine genes by interferon-γ (IFN-γ) and Toll-like receptor (TLR) signaling is important for innate immunity and inflammatory disease pathogenesis. Enhancement of TLR signaling, a previously proposed mechanism, is insufficient to explain strong synergistic activation of cytokine production in human macrophages. Rather, we found that IFN-γ induced sustained occupancy of transcription factors STAT1, IRF-1, and associated histone acetylation at promoters and enhancers at the TNF, IL6, and IL12B loci. This priming of chromatin did not activate transcription but greatly increased and prolonged recruitment of TLR4-induced transcription factors and RNA polymerase II to gene promoters and enhancers. Priming sensitized cytokine transcription to suppression by Jak inhibitors. Genome-wide analysis revealed pervasive priming of regulatory elements by IFN-γ and linked coordinate priming of promoters and enhancers with synergistic induction of transcription. Our results provide a synergy mechanism whereby IFN-γ creates a primed chromatin environment to augment TLR-induced gene transcription.

Lessons for the clinic from rituximab pharmacokinetics and pharmacodynamics

The anti-CD20 antibody rituximab (RTX; Rituxan®, MabThera®) was the first anti-cancer antibody approved by the US Food and Drug Administration in 1997 and it is now the most-studied unconjugated therapeutic antibody. The knowledge gained over the past 15 y on the pharmacodynamics (PD) of this antibody has led to the development of a new generation of anti-CD20 antibodies with enhanced efficacy in vitro. Studies on the pharmacokinetics (PK) properties and the effect of factors such as tumor load and localization, antibody concentration in the circulation and gender on both PK and clinical response has allowed the design of optimized schedules and novel routes of RTX administration. Although clinical results using newer anti-CD20 antibodies, such as ofatumumab and obinutuzumab, and novel administration schedules for RTX are still being evaluated, the knowledge gained so far on RTX PK and PD should also be relevant for other unconjugated monoclonal antibody therapeutics, and will be critically reviewed here.

Immune-regulatory mechanisms in systemic autoimmune and rheumatic diseases

Systemic autoimmune and rheumatic diseases (SAIRDs) are thought to develop due to the failure of autoimmune regulation and tolerance. Current therapies, such as biologics, have improved the clinical results of SAIRDs; however, they are not curative treatments. Recently, new discoveries have been made in immune tolerance and inflammation, such as tolerogenic dendritic cells, regulatory T and B cells, Th 17 cells, inflammatory and tolerogenic cytokines, and intracellular signaling pathways. They lay the foundation for the next generation of the therapies beyond the currently used biologic therapies. New drugs should target the core processes involved in disease mechanisms with the aim to attain complete cure combined with safety and low costs compared to the biologic agents. Re-establishment of autoimmune regulation and tolerance in SAIRDs by the end of the current decade should be the final and realistic target.

Emerging immunological targets in inflammatory bowel disease

Crohn's disease (CD) and ulcerative colitis (UC) are the major forms of inflammatory bowel diseases (IBD) in man. They are caused by damage to the lining of the intestine and deeper layers, due to an excessive immune response directed against components of the gut microflora and poorly controlled by counter-regulatory mechanisms. CD and UC are however immunologically distinct. CD-related inflammation is characterized by a marked mucosal infiltration of T lymphocytes secreting T helper type (Th) 1 and Th17 cytokines. In UC, the local immune response is less polarized but may show enhanced production of IL-5, IL-13 and Th17 cytokines. Downstream however CD and UC share important end-stage effector pathways of intestinal injury, mediated by an active cross-talk between immune and non-immune cells. The clarification of the complex networks of immune-inflammatory mediators operating in the gut of IBD patients has led to the identification of new targets that should facilitate the development of novel biological therapies.

Cytokine modulators in the treatment of sarcoidosis

Sarcoidosis is a granulomatous lung disease in which several cytokines play a pivotal pathogenetic role. Steroid-resistant disease can be treated with immunosuppressive drugs, antimalarial therapies and recently with anti-TNFα agents. The use of biological agents for the treatment of sarcoidosis springs from research into the pathogenesis of the disease and also from the experience of rheumatologists with other chronic inflammatory diseases. Rituximab, golimumab and ustekinumab are cytokine modulators, useful in the treatment of immunoinflammatory disorders, for which randomized trials to evaluate safety and efficacy in sarcoidosis are not yet available. Novel anticytokine drugs administered alone or in association may offer a new approach to treatment of the disease. This review focuses on recent advances in anti-TNFα agents and cytokine modulators for the treatment of sarcoidosis and their therapeutic prospects.

Pernicious anemia - genetic insights

Pernicious anemia (PA) is a complex, autoimmune, multi-factorial disease. Rapid progress has been made in the understanding of susceptibility to a spectrum of other autoimmune diseases through genome wide association studies (GWAS). However, PA has been conspicuous by its absence from this work. Here, we examine the evidence that PA has a significant heritable component through epidemiological evidence and its co-occurrence with other autoimmune diseases. Further, we consider how knowledge of the genetic susceptibility to other autoimmune diseases may provide insight into the etiology of PA.

Emerging small molecule and biological therapeutic approaches for the treatment of autoimmunity

IMPORTANCE OF THE FIELD

Biological therapeutics targeting TNF-α, IL-6, CD20 and CD80/86 is proving to be an important weapon in the clinicians' armory to fight autoimmunity alongside long-standing small molecule therapeutics such as methotrexate and glucocorticoids. However, there still remains a high unmet clinical need in the field of autoimmunity and many researchers are continuing to discover and develop new therapeutics to address this.

AREAS COVERED IN THIS REVIEW

A new wave of small molecule and biological therapeutics targeting different pathways is being developed which could generate exciting new options for clinicians. This review aims to highlight those emerging therapies that are most advanced in clinical development.

WHAT THE READER WILL GAIN

The reader will gain an appreciation of new approaches being developed to address the high unmet clinical need in the field of autoimmunity.

TAKE HOME MESSAGE

Despite recent success in the development of therapeutics to treat autoimmunity, new therapeutic strategies are being developed to address the remaining areas of a high unmet clinical need.

Conference Scene: Highlights of the 7th Autoimmunity Congress

This meeting was dedicated to various autoimmune diseases and their mechanisms, diagnosis and therapies. The autoimmunity-promoting factors included genetic variations and environmental injuries. A broad array of cytokines, including the B-cell activating factor, and autoantibodies, including novel specificities, were discussed. Finally, new horizons in treatment, including tolerogenic peptides, intravenous immunoglobulin and B-cell-depleting agents, were presented.

B1 cells promote pancreas infiltration by autoreactive T cells

The entry of autoreactive T cells into the pancreas is a critical checkpoint in the development of autoimmune diabetes. In this study, we identify a role for B1 cells in this process using the DO11 x RIP-mOVA mouse model. In transgenic mice with islet-specific T cells, but no B cells, T cells are primed in the pancreatic lymph node but fail to enter the pancreas. Reconstitution of the B1 cell population by adoptive transfer permits extensive T cell pancreas infiltration. Reconstituted B1 cells traffic to the pancreas and modify expression of adhesion molecules on pancreatic vasculature, notably VCAM-1. Despite substantial pancreas infiltration, islet destruction is minimal unless regulatory T cells are depleted. These data identify a role for B1 cells in permitting circulating islet-specific T cells to access their Ag-bearing tissue and emphasize the existence of multiple checkpoints to regulate autoimmune disease.

CD28 co-signaling in the adaptive immune response

T-cell proliferation and function depends on signals from the antigen-receptor complex (TCR/CD3) and by various co-receptors such as CD28 and CTLA-4. The balance of positive and negative signals determines the outcome of the T-cell response to foreign and self-antigen. CD28 is a prominent co-receptor in naïve and memory T-cell responses. Its blockade has been exploited clinically to dampen T-cell responses to self-antigen. Current evidence shows that CD28 both potentiates TCR signaling and engages a unique array of mediators (PI3K, Grb2, FLNa) in the regulation of aspects of T-cell signaling including the transcription factor NFkB. In this mini-review, we provide an up-to-date overview of our understanding of the signaling mechanisms that underlie CD28 function and its potential application to the modulation of reactivity to autoimmunity.

Cytokines as therapeutic targets in SLE

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease involving most immune cells. Studies in both experimental animal models of lupus and patients with SLE have revealed a number of cytokine pathways that are important in the disease process. Among these are B-cell activating factor, which promotes B-cell survival and autoantibody production, interferon-alpha, which acts as an immune adjuvant, and tumor necrosis factor, which contributes to organ inflammation. This knowledge, in combination with the successful use of anti-TNF treatment in rheumatoid arthritis, has spurred the development of several biologic agents targeting different cytokines or their receptors in SLE. Consequently, many trials of anticytokine therapies for SLE are underway. Although most of these trials are small or in early phases, the results of some large studies have also been reported. In this Review, we discuss the rationale for anticytokine therapies in SLE and review agents currently in use, and those being developed and tested experimentally. We present the results from published trials and discuss the tentative conclusions that can be drawn regarding the efficacy of the new agents. Finally, we provide suggestions for the future of treatment for SLE, including new therapeutic strategies.

Safety and immunotoxicity assessment of immunomodulatory monoclonal antibodies

Most therapeutic monoclonal antibodies (mAbs) licensed for human use or in clinical development are indicated for treatment of patients with cancer and inflammatory/autoimmune disease and as such, are designed to directly interact with the immune system. A major hurdle for the development and early clinical investigation of many of these immunomodulatory mAbs is their inherent risk for adverse immune-mediated drug reactions in humans such as infusion reactions, cytokine storms, immunosuppression and autoimmunity. A thorough understanding of the immunopharmacology of a mAb in humans and animals is required to both anticipate the clinical risk of adverse immunotoxicological events and to select a safe starting dose for first-in-human (FIH) clinical studies. This review summarizes the most common adverse immunotoxicological events occurring in humans with immunomodulatory mAbs and outlines non-clinical strategies to define their immunopharmacology and assess their immunotoxic potential, as well as reduce the risk of immunotoxicity through rational mAb design. Tests to assess the relative risk of mAb candidates for cytokine release syndrome, innate immune system (dendritic cell) activation and immunogenicity in humans are also described. The importance of selecting a relevant and sensitive toxicity species for human safety assessment in which the immunopharmacology of the mAb is similar to that expected in humans is highlighted, as is the importance of understanding the limitations of the species selected for human safety assessment and supplementation of in vivo safety assessment with appropriate in vitro human assays. A tiered approach to assess effects on immune status, immune function and risk of infection and cancer, governed by the mechanism of action and structural features of the mAb, is described. Finally, the use of immunopharmacology and immunotoxicity data in determining a minimum anticipated biologic effect Level (MABEL) and in the selection of safe human starting dose is discussed.

Control of metabolism and signaling of simple bioactive sphingolipids: Implications in disease

Simple bioactive sphingolipids include ceramide, sphingosine and their phosphorylated forms sphingosine 1-phosphate and ceramide 1-phosphate. These molecules are crucial regulators of cell functions. In particular, they play important roles in the regulation of angiogenesis, apoptosis, cell proliferation, differentiation, migration, and inflammation. Decoding the mechanisms by which these cellular functions are regulated requires detailed understanding of the signaling pathways that are implicated in these processes. Most importantly, the development of inhibitors of the enzymes involved in their metabolism may be crucial for establishing new therapeutic strategies for treatment of disease.