Autologous attenuated T-cell vaccine (Tovaxin®) dose escalation in multiple sclerosis relapsing–remitting and secondary progressive patients nonresponsive to approved immunomodulatory therapies

Safety and efficacy of antigen-specific therapeutic approaches for multiple sclerosis: Systematic review

INTRODUCTION

The objective of this systematic review is to evaluate the efficacy and safety of antigen-specific tolerance-inducing therapeutic approaches (products based on peptides, DNA and T cells) versus placebo or other comparators, where possible, in adult multiple sclerosis (MS) patients.

METHODS

PubMed, CINAHL, Web of Science, Cochrane and International Clinical Trials Registry Platform, ClinicalTrials.gov were searched for published and unpublished studies. Screening, critical appraisal, and data extraction for included studies were carried out by two independent reviewers. For efficacy, phase I, II and III clinical trials (randomized/non-randomized; double blind/single blind/unblinded; single-center/multicenter; single-arm/two-arm) and for safety, phase I, II and III clinical trials (randomized/non-randomized; double blind/single blind/unblinded; controlled/uncontrolled; single-center/multicenter; single-arm/two-arm) were included. Observational studies (cross-sectional studies, cohort studies, case studies/reports etc), review articles, systematic reviews, meta-analysis, preclinical and pilot studies were excluded. All included studies were critically appraised using standardized JBI tools, with no exclusions based on methodological quality. Where possible, studies were pooled in statistical meta-analysis, presented in tabular format, and accompanied by narrative synthesis. The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach for grading the certainty of evidence.

RESULTS

Search yielded 2644 results and in total 26 studies were included in the final analysis. Twelve studies were RCTs and 14 were quasi-experimental. In total, there were 1427 subjects from the RCTs, and 314 from non-RCTs. Sample size of studies ranged from 10 to 612 patients. All studies included adult patients, principally aged 18-55/65 years. Critical appraisal scores for the RCTs were in the range 31% to 92%. For quasi-experimental studies, critical appraisal scores were in the range 45% to 78%. Due to high heterogeneity of the studies, efficacy of all antigen-specific treatment remained ambiguous. For all three types of treatment, there was no statistical difference in occurrence of adverse effects (AEs) between the treatment- and placebo-related AEs (for DNA-based treatment RR was 1.06 (0.94-1.10), p = 0.334; for peptides-base treatments RR was 1.04 (0.90-1.08), p = 0.115; for T-cells-based treatments RR was 1.31 (0.97-1.76), p = 0.08). There were no differences in RR for serious AEs (SAEs) between the treatments either for DNA-based treatment (RR was 0.63 (0.25-1.58), p = 0.322) or peptide-based treatment (RR was 0.86 (0.62-1.19), p = 0.361). There were no reported SAEs for T cell-based treatments, so meta-analysis for these therapies was not performed. The most frequent AEs were local reactions to injection, such as redness, erythema, pain.

DISCUSSION

Antigen-specific tolerance-inducing therapeutic approaches appeared to be safe. However, the certainty for these results was very low for SAEs in peptide- and DNA-based therapies, whereas it was low for AEs in DNA- and T cells-based therapies and moderate for AEs in peptide-based therapies. The efficacy of antigen-specific therapies remains ambiguous. Larger, well-designed studies with high level quality are needed to ensure ultimate conclusions.

REGISTRATION

The registration number provided following registration of the protocol in PROSPERO is 'CRD42021236776'.

Paving the way towards an effective treatment for multiple sclerosis: advances in cell therapy

Multiple sclerosis (MS) is a leading cause of chronic neurological disability in young to middle-aged adults, affecting ~2.5 million people worldwide. Currently, most therapeutics for MS are systemic immunosuppressive or immunomodulatory drugs, but these drugs are unable to halt or reverse the disease and have the potential to cause serious adverse events. Hence, there is an urgent need for the development of next-generation treatments that, alone or in combination, stop the undesired autoimmune response and contribute to the restoration of homeostasis. This review analyzes current MS treatments as well as different cell-based therapies that have been proposed to restore homeostasis in MS patients (tolerogenic dendritic cells, regulatory T cells, mesenchymal stem cells, and vaccination with T cells). Data collected from preclinical studies performed in the experimental autoimmune encephalomyelitis (EAE) model of MS in animals, in vitro cultures of cells from MS patients and the initial results of phase I/II clinical trials are analyzed to better understand which parameters are relevant for obtaining an efficient cell-based therapy for MS.

Failed, Interrupted, or Inconclusive Trials on Immunomodulatory Treatment Strategies in Multiple Sclerosis: Update 2015-2020

In the past decades, multiple sclerosis (MS) treatment has experienced vast changes resulting from major advances in disease-modifying therapies (DMT). Looking at the overall number of studies, investigations with therapeutic advantages and encouraging results are exceeded by studies of promising compounds that failed due to either negative or inconclusive results or have been interrupted for other reasons. Importantly, these failed clinical trials are informative experiments that can help us to understand the pathophysiological mechanisms underlying MS. In several trials, concepts taken from experimental models were not translatable to humans, although they did not lack a well-considered pathophysiological rationale. The lessons learned from these discrepancies may benefit future studies and reduce the risks for patients. This review summarizes trials on MS since 2015 that have either failed or have been interrupted for various reasons. We identify potential causes of failure or inconclusiveness, looking at the path from basic animal experiments to clinical trials, and discuss the implications for our current view on MS pathogenesis, clinical practice, and future study designs. We focus on anti-inflammatory treatment strategies, without including studies on already approved and effective DMT. Clinical trials addressing neuroprotective and alternative treatment strategies are presented in a separate article.

Antigen-Specific Immune Tolerance in Multiple Sclerosis-Promising Approaches and How to Bring Them to Patients

Antigen-specific tolerance induction aims at treating multiple sclerosis (MS) at the root of its pathogenesis and has the prospect of personalization. Several promising tolerization approaches using different technologies and modes of action have already advanced to clinical testing. The prerequisites for successful tolerance induction include the knowledge of target antigens, core pathomechanisms, and how to pursue a clinical development path that is distinct from conventional drug development. Key aspects including patient selection, outcome measures, demonstrating the mechanisms of action as well as the positioning in the rapidly growing spectrum of MS treatments have to be considered to bring this therapy to patients.

Recent Advances in Antigen-Specific Immunotherapies for the Treatment of Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system and is considered to be the leading non-traumatic cause of neurological disability in young adults. Current treatments for MS comprise long-term immunosuppressant drugs and disease-modifying therapies (DMTs) designed to alter its progress with the enhanced risk of severe side effects. The Holy Grail for the treatment of MS is to specifically suppress the disease while at the same time allow the immune system to be functionally active against infectious diseases and malignancy. This could be achieved via the development of immunotherapies designed to specifically suppress immune responses to self-antigens (e.g., myelin antigens). The present study attempts to highlight the various antigen-specific immunotherapies developed so far for the treatment of multiple sclerosis (e.g., vaccination with myelin-derived peptides/proteins, plasmid DNA encoding myelin epitopes, tolerogenic dendritic cells pulsed with encephalitogenic epitopes of myelin proteins, attenuated autologous T cells specific for myelin antigens, T cell receptor peptides, carriers loaded/conjugated with myelin immunodominant peptides, etc), focusing on the outcome of their recent preclinical and clinical evaluation, and to shed light on the mechanisms involved in the immunopathogenesis and treatment of multiple sclerosis.

Molecular Interventions towards Multiple Sclerosis Treatment

Multiple sclerosis (MS) is an autoimmune life-threatening disease, afflicting millions of people worldwide. Although the disease is non-curable, considerable therapeutic advances have been achieved through molecular immunotherapeutic approaches, such as peptides vaccination, administration of monoclonal antibodies, and immunogenic copolymers. The main aims of these therapeutic strategies are to shift the MS-related autoimmune response towards a non-inflammatory T helper 2 (Th2) cells response, inactivate or ameliorate cytotoxic autoreactive T cells, induce secretion of anti-inflammatory cytokines, and inhibit recruitment of autoreactive lymphocytes to the central nervous system (CNS). These approaches can efficiently treat autoimmune encephalomyelitis (EAE), an essential system to study MS in animals, but they can only partially inhibit disease progress in humans. Nevertheless, modern immunotherapeutic techniques remain the most promising tools for the development of safe MS treatments, specifically targeting the cellular factors that trigger the initiation of the disease.

Infections, Vaccines and Autoimmunity: A Multiple Sclerosis Perspective

Background: Multiple sclerosis (MS) is a chronic neuroinflammatory and neurodegenerative disease that is associated with multiple environmental factors. Among suspected susceptibility events, studies have questioned the potential role of overt viral and bacterial infections, including the Epstein Bar virus (EBV) and human endogenous retroviruses (HERV). Furthermore, the fast development of immunomodulatory therapies further questions the efficacy of the standard immunization policies in MS patients. Topics reviewed: This narrative review will discuss the potential interplay between viral and bacterial infections and their treatment on MS susceptibility and disease progression. In addition, the review specifically discusses the interactions between MS pathophysiology and vaccination for hepatitis B, influenza, human papillomavirus, diphtheria, pertussis, and tetanus (DTP), and Bacillus Calmette-Guerin (BCG). Data regarding potential interaction between MS disease modifying treatment (DMT) and vaccine effectiveness is also reviewed. Moreover, HERV-targeted therapies such as GNbAC1 (temelimab), EBV-based vaccines for treatment of MS, and the current state regarding the development of T-cell and DNA vaccination are discussed. Lastly, a reviewing commentary on the recent 2019 American Academy of Neurology (AAN) practice recommendations regarding immunization and vaccine-preventable infections in the settings of MS is provided. Conclusion: There is currently no sufficient evidence to support associations between standard vaccination policies and increased risk of MS. MS patients treated with immunomodulatory therapies may have a lower benefit from viral and bacterial vaccination. Despite their historical underperformance, new efforts in creating MS-based vaccines are currently ongoing. MS vaccination programs follow the set back and slow recovery which is widely seen in other fields of medicine.

Beyond the Magic Bullet: Current Progress of Therapeutic Vaccination in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic immune-mediated disease of the central nervous system (CNS) characterized by neuroinflammation, neurodegeneration and impaired repair mechanisms that lead to neurological disability. The crux of MS is the patient's own immune cells attacking self-antigens in the CNS, namely the myelin sheath that protects nerve cells of the brain and spinal cord. Restoring antigen-specific tolerance via therapeutic vaccination is an innovative and exciting approach in MS therapy. Indeed, leveraging the body's attempt to prevent autoimmunity, i.e., tolerization, focuses on the underlying cause of the disease and could be the key to solving neuroinflammation. In this perspective, antigen-specific vaccination targets only the detrimental and aberrant immune response against the specific disease-associated antigen(s) involved while retaining the capacity of the immune system to respond to unrelated antigens. We review the experimental approaches of tolerance-inducing vaccination in relapsing and progressive forms of MS that have reached the clinical development phase, including vaccination with autologous T cells, autologous tolerogenic dendritic cells, T cell receptor peptide vaccination, altered peptide ligand, ATX-MS-1467, cluster of differentiation (CD)-206-targeted liposomal myelin basic protein peptides and DNA vaccination. Failures, successes and future directions are discussed.

Further understanding of the immunopathology of multiple sclerosis: impact on future treatments

INTRODUCTION

The understanding of the immunopathogenesis of multiple sclerosis (MS) has expanded with more research into T-cell subtypes, cytokine contributors, B-cell participation, mitochondrial dysfunction, and more. Treatment options have rapidly expanded with three relatively recent oral therapy alternatives entering the arena.

AREAS COVERED

In the following review, we discuss current mechanisms of immune dysregulation in MS, how they relate to current treatments, and the impact these findings will have on the future of therapy. Expert commentary: The efficacy of these medications and understanding their mechanisms of actions validates the immunopathogenic mechanisms thought to underlie MS. Further research has exposed new targets, while new promising therapies have shed light on new aspects into the pathophysiology of MS.

Neuroimmunotherapies Targeting T Cells: From Pathophysiology to Therapeutic Applications

Therapeutic options for multiple sclerosis (MS) have significantly increased over the last few years. T lymphocytes are considered to play a central role in initiating and perpetuating the pathological immune response. Currently approved therapies for MS target T lymphocytes, either in an unspecific manner or directly by interference with specific T-cell pathways. While the concept of "T-cell-specific therapy" implies specificity and selectivity, currently approved approaches come from a general shaping of the immune system towards anti-inflammatory immune responses by non-T-cell-selective immune suppression or immune modulation (e.g., interferons-immune modulation approach) to a depletion of immune cell populations involving T cells (e.g., anti-CD52, alemtuzumab-immune selective depletion approach), or a selective inhibition of distinct molecular pathways in order to sequester leucocytes (e.g., natalizumab-leukocyte sequestration approach). This review will highlight the rationale and results of different T-cell-directed therapeutic approaches coming from basic animal experiments to clinical trials. We will first discuss the pathophysiological rationale for targeting T lymphocytes in MS leading to currently approved treatments acting on T lymphocytes. Furthermore, we will disuss previous promising concepts that have failed to show efficacy in clinical trials or were halted as a result of unexpected adverse events. Learning from the discrepancies between expectations and failures in practical outcomes helps to optimize future research approaches and clinical study designs. As our current view of MS pathogenesis and patient needs is rapidly evolving, novel therapeutic approaches targeting T lymphocytes will also be discussed, including specific molecular interventions such as cytokine-directed treatments or strategies enhancing immunoregulatory mechanisms. Based on clinical experience and novel pathophysiological approaches, T-cell-based strategies will remain a pillarstone of MS therapy.

The search for the target antigens of multiple sclerosis, part 1: autoreactive CD4+ T lymphocytes as pathogenic effectors and therapeutic targets

Identification of the target antigens of pathogenic antibodies and T cells is of fundamental importance for understanding the pathogenesis of multiple sclerosis, and for the development of personalised treatments for the disease. Myelin-specific CD4+ T cells emerged long ago as a key player in animal models of multiple sclerosis. Taking a forward-translational approach, autoreactive CD4+ T cells have been studied extensively in patients with multiple sclerosis, and there is evidence, but as yet no direct proof, that autoreactive CD4+ T cells are a key player in the pathogenesis of the disorder. Several therapies that selectively target myelin-specific CD4+ T cells have been investigated in clinical trials up to phase 3. So far, however, none of these (mostly underpowered) therapeutic trials have provided definitive evidence of clinical efficacy. One major obstacle to personalised, highly selective immunotherapy is the absence of standardised and reliable assays to assess antigen-specific human T-cell responses. Such assays would be essential for stratification of patients with multiple sclerosis according to their individual target antigens.

The mechanisms and applications of T cell vaccination for autoimmune diseases: a comprehensive review

Autoimmune diseases (ADs) are a spectrum of diseases originating from loss of immunologic self-tolerance and T cell abnormal autoreactivity, causing organ damage and death. However, the pathogenic mechanism of ADs remains unclear. The current treatments of ADs include nonsteroidal anti-inflammatory drugs (NSAIDS), antimalarials, corticosteroids, immunosuppressive drugs, and biological therapies. With the need to prevent side effects resulting from current treatments and acquire better clinical remission, developing a novel pharmaceutical treatment is extremely urgent. The concept of T cell vaccination (TCV) has been raised as the finding that immunization with attenuated autoreactive T cells is capable of inducing T cell-dependent inhibition of autoimmune responses. TCV may act as an approach to control unwanted adaptive immune response through eliminating the autoreactive T cells. Over the past decades, the effect of TCV has been justified in several animal models of autoimmune diseases including experimental autoimmune encephalomyelitis (EAE), murine autoimmune diabetes in nonobese diabetic (NOD) mice, collagen-induced arthritis (CIA), and so on. Meanwhile, clinical trials of TCV have confirmed the safety and efficacy in corresponding autoimmune diseases ranging from multiple sclerosis (MS) to systemic lupus erythematosus (SLE). This review aims to summarize the ongoing experimental and clinical trials and elucidate possible molecule mechanisms of TCV.

Therapeutic approaches to disease modifying therapy for multiple sclerosis in adults: an Australian and New Zealand perspective: part 1 historical and established therapies. MS Neurology Group of the Australian and New Zealand Association of Neurologists

Multiple sclerosis (MS) is a potentially life-changing immune mediated disease of the central nervous system. Until recently, treatment has been largely confined to acute treatment of relapses, symptomatic therapies and rehabilitation. Through persistent efforts of dedicated physicians and scientists around the globe for 160 years, a number of therapies that have an impact on the long term outcome of the disease have emerged over the past 20 years. In this three part series we review the practicalities, benefits and potential hazards of each of the currently available and emerging treatment options for MS. We pay particular attention to ways of abrogating the risks of these therapies and provide advice on the most appropriate indications for using individual therapies. In Part 1 we review the history of the development of MS therapies and its connection with the underlying immunobiology of the disease. The established therapies for MS are reviewed in detail and their current availability and indications in Australia and New Zealand are summarised. We examine the evidence to support their use in the treatment of MS.

Antigen-specific tolerization approaches in multiple sclerosis

INTRODUCTION

Inhibition of self-reactive T cells through induction of antigen-specific immune tolerance holds the promise of effective treatment of autoimmune pathology with few side effects and preservation of normal immune functions. In multiple sclerosis (MS) several approaches have been tested already in clinical trials or are currently ongoing with the aim to inhibit myelin-reactive immune responses.

AREAS COVERED

This article provides an overview of the recent and ongoing strategies to inhibit specific immune responses in MS, including different applications of myelin peptide-based approaches, T-cell vaccination, DNA vaccination and antigen-coupled cells.

EXPERT OPINION

Despite difficulties in translation of antigen-specific therapies in MS, novel approaches have the potential to effectively induce immune tolerance and ameliorate the disease. To improve efficacy of treatments, future trials should include patients in the early phases of the disease, when the autoimmune response is predominant and immune reactivity still focused. The target antigens are not fully defined yet, and robust immunomonitoring assays should developed to provide mechanistic proof of concept in parallel to showing efficacy with respect to inhibiting inflammatory disease activity in the central nervous system (CNS).

CD8+ regulatory T cells induced by T cell vaccination protect against autoimmune nephritis

Autoreactive T cells play a pivotal role in the pathogenesis of autoimmune kidney disease. T cell vaccination (TCV) may limit autoimmune disease and induce CD8+ regulatory T cells (Tregs). We used Heymann nephritis (HN), a rat model of human membranous nephritis, to study the effects of TCV on autoimmune kidney disease. We harvested CD4+ T cells from renal tubular antigen (Fx1A) -immunized rats and activated these cells in vitro to express the MHC Class Ib molecule Qa-1. Vaccination of Lewis rats with these autoreactive Fx1A-induced T cells protected against HN, whereas control-primed T cells did not. Rats that underwent TCV had lower levels of proteinuria and serum creatinine and significantly less glomerulosclerosis, tubular damage, and interstitial infiltrates. Furthermore, these rats expressed less IFN-γ and IL-6 in splenocytes, whereas the numbers of Tregs and the expression of Foxp3 were unchanged. In vitro cytotoxicity assays showed CD8+ T cell-mediated elimination of Qa-1-expressing CD4+ T cells. In vivo, TCV abrogated the increase in Qa-1-expressing CXCR5+ TFH cells observed in HN compared with controls. Taken together, these results suggest that TCV protects against autoimmune kidney disease by targeting Qa-1-expressing autoreactive CD4+ cells.

A randomized clinical trial of autologous T-cell therapy in multiple sclerosis: subset analysis and implications for trial design

Background: Tovaxin is an autologous T-cell immunotherapy under investigation for the treatment of MS. The product consists of in vitro expanded myelin-reactive T-cells manufactured against up to six immunodominant peptides derived from three myelin antigens.

Methods: A Phase 2b placebo controlled study (TERMS) was conducted in 150 subjects to gather safety and efficacy data in relapsing-remitting MS and clinically isolated syndrome subjects.

Results: Tovaxin had a favorable safety profile. Although no statistically significant clinical or radiological benefit of Tovaxin immunotherapy was identified in the modified intent-to-treat population, a prospective analysis of subjects with more active disease favored Tovaxin in terms of annualized relapse rate (ARR) and disability progression. An analysis also found a possible legacy effect of prior disease-modifying treatment (DMT) which may have contributed to a lowered ARR in the placebo group. DMT-naïve subjects treated with Tovaxin had a lower ARR compared to the placebo group, particularly in those with active baseline disease (ARR≥1, ARR>1). However, clinical benefit was not was accompanied by a treatment-dependent improvement in MRI measures.

Conclusions: Previous DMT exposure may reduce effect size and study power. Limiting subject selection to DMT-treatment-naïve individuals may be a reasonable approach to phase 2 or proof-of-concept studies of limited duration.

Regulatory T cells play a role in T-cell receptor CDR2 peptide regulation of experimental autoimmune encephalomyelitis

Eliciting T-cell receptor (TCR) -specific responsiveness has been known to provide an effective autoregulatory mechanism for limiting inflammation mediated by T effector cells. Our previous use of TCR peptides derived from the CDR3 regions of a pathogenic TCR effectively reversed ongoing experimental autoimmune encephalomyelitis (EAE) in a humanized TCR transgenic model. In this study, we use the TCR BV8S2 CDR2 peptide in the non-transgenic C57BL/6 EAE model to down-regulate the heterogeneous TCR BV8S2(+)  MOG-35-55-specific pathogenic T-cell population and demonstrate successful treatment of EAE after disease onset. Suppression of disease was associated with reduced MOG-35-55-specific and non-specific T-cell production of interleukin-17a and interferon-γ in the central nervous system, as well as reduced numbers of CD4(+) and Foxp3(+) T cells in the central nervous system. With the use of Foxp3-GFP and Foxp3 conditional knockout mice, we demonstrate that the TCR CDR2 peptide treatment effect is dependent on the presence of Foxp3(+) regulatory T cells and that regulatory T cell numbers are significantly expanded in the periphery of treated mice. Hence, TCR CDR2 peptide therapy is effective in regulating heterogeneous, pathogenic T-cell populations through the activity of the Foxp3(+) regulatory T cell population.

Chronic progressive multiple sclerosis - pathogenesis of neurodegeneration and therapeutic strategies

Multiple sclerosis (MS) is an inflammatory, autoimmune, demyelinating disease of the central nervous system (CNS) that usually starts as a relapsing-remitting disease. In most patients the disease evolves into a chronic progressive phase characterized by continuous accumulation of neurological deficits. While treatment of relapsing-remitting MS (RRMS) has improved dramatically over the last decade, the therapeutic options for chronic progressive MS, both primary and secondary, are still limited. In order to find new pharmacological targets for the treatment of chronic progressive MS, the mechanisms of the underlying neurodegenerative process that becomes apparent as the disease progresses need to be elucidated. New animal models with prominent and widespread progressive degenerative components of MS have to be established to study both inflammatory and non-inflammatory mechanisms of neurodegeneration. Here, we discuss disease mechanisms and treatment strategies for chronic progressive MS.

Tovaxin for multiple sclerosis

INTRODUCTION

A potential therapeutic possibility for multiple sclerosis (MS) is provided by Tovaxin, a personalized autologous T-cell immunotherapy utilizing myelin-reactive lymphocytes from peripheral blood.

AREAS COVERED

This review covers the production of the vaccine, which follows a series of steps after the acquisition of T-cells. This includes identification of the subsets that are myelin reactive, expansion ex vivo and, also extrinsically, inactivation of their replication capacity by cellular irradiation. Once attenuated, the modified cells are reintroduced into the donor. This process appears to induce a vigorous immune response towards specific populations of autoreactive T-cells determined to attack the myelin and its derivatives by trafficking from the vascular space into the CNS in MS. Historical aspects of the T-cell vaccination with Tovaxin, the process to obtain reactive T-cells and their attenuation techniques ex vivo are described. The clinical results obtained from clinical trials are also discussed.

EXPERT OPINION

The process of T-cell vaccination is complicated and presents some limitations. Further studies are required to provide scientific support and clinical evidence of the efficacy of Tovaxin in MS.

Multiple Sclerosis

Multiple sclerosis, an autoimmune disorder causing the destruction of the impulse carrying myelin sheath of neurons, can be a debilitating and disabling disease. Symptomatic treatment has provided patients with relief through the use of antispasmodics, anticholinergics, and antidepressants, just to name a few, as well as disease treatment by decreasing progression of the illness by treating acute episodes through the use of corticosteroids, interferons, plasmapheresis, and other immunomodulators like glatiramer, mitoxantrone, and natalizumab. With medical advancements and the development of new treatments such as laquinimod, fampridine-SR, and several others, the future looks promising for those living with this illness.

Antigen-specific therapies in multiple sclerosis

BACKGROUND

If found to be effective, antigen-specific therapies in MS hold the promise of selectively targeting pathogenic effector cells, while leaving the rest of immune system undisturbed.

OBJECTIVE

To review the principles and challenges of antigen-specific therapies of the past and those presently under development, and how the lessons learnt can guide us moving forward.

METHODS

We review past and current antigen-specific strategies for the treatment of MS, including their successes and challenges, as well as the lessons we have learnt from them about MS pathophysiology.

RESULTS

Several antigen-specific therapies may accomplish the desired balance between safety and efficacy, although significant challenges remain for this class of therapeutics.