Trials of antivirals in the treatment of multiple sclerosis

Endogenous retroviruses in multiple sclerosis: A network-based etiopathogenic model

The present perspective article proposes an etiopathological model for multiple sclerosis pathogenesis and progression associated with the activation of human endogenous retroviruses. We reviewed preclinical, clinical, epidemiological, and evolutionary evidence indicating how the complex, multi-level interplay of genetic traits and environmental factors contributes to multiple sclerosis. We propose that endogenous retroviruses transactivation acts as a critical node in disease development. We also discuss the rationale for combined anti-retroviral therapy in multiple sclerosis as a disease-modifying therapeutic strategy. Finally, we propose that the immuno-pathogenic process triggered by endogenous retrovirus activation can be extended to aging and aging-related neurodegeneration. In this regard, endogenous retroviruses can be envisioned to act as epigenetic noise, favoring the proliferation of disorganized cellular subpopulations and accelerating system-specific "aging". Since inflammation and aging are two sides of the same coin (plastic dis-adaptation to external stimuli with system-specific degree of freedom), the two conditions may be epiphenomenal products of increased epigenomic entropy. Inflammation accelerates organ-specific aging, disrupting communication throughout critical systems of the body and producing symptoms. Overlapping neurological symptoms and syndromes may emerge from the activity of shared molecular networks that respond to endogenous retroviruses' reactivation.

How to and should we target EBV in MS?

INTRODUCTION

The etiology of multiple sclerosis (MS) remains unknown. Pathogenesis likely relies on a complex interaction between multiple environmental, genetic, and behavioral risk factors. However, a growing body of literature supports the role of a preceding Epstein-Barr virus (EBV) infection in the majority of cases.

AREAS COVERED

In this narrative review, we summarize the latest findings regarding the potential role of EBV as a predisposing event inducing new onset of MS. EBV interactions with the genetic background and other infectious agents such as human endogenous retrovirus are explored. Additional data regarding the role of EBV regarding the rate of mid- and long-term disease progression is also discussed. Lastly, the effect of currently approved disease-modifying therapies (DMT) for MS treatment on the EBV-based molecular mechanisms and the development of new EBV-specific therapies are further reviewed.

EXPERT OPINION

Recent strong epidemiological findings support that EBV may be the primary inducing event in certain individuals that shortly thereafter develop MS. More studies are needed in order to better understand the significant variability in susceptibility based on environmental factors such as EBV exposure. Future investigations should focus on determining the specific EBV-related risk antigen(s) and phenotyping people with likely EBV-induced MS. Targeting EBV via several different avenues, including development of an EBV vaccine, may become the mainstay of MS treatment in the future.

Insights into the interplay between Epstein-Barr virus (EBV) and multiple sclerosis (MS): A state-of-the-art review and implications for vaccine development

Background and Aims

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS). MS results from an inflammatory process leading to the loss of neural tissue and increased disability over time. The role of Epstein Barr Virus (EBV), as one of the most common global viruses, in MS development has been the subject of several studies. However, many related questions are still unanswered. This study aimed to review the connection between MS and EBV and provide a quick outline of MS prevention using EBV vaccination.

Methods

For this narrative review, an extensive literature search using specific terms was conducted across online databases, including PubMed/Medline, Scopus, Web of Science, and Google Scholar, to identify pertinent studies.

Results

Several studies proved that almost 100% of people with MS showed a history of EBV infection, and there was an association between high titers of EBV antibodies and an increased risk of MS development. Various hypotheses are proposed for how EBV may contribute to MS directly and indirectly: (1) Molecular Mimicry, (2) Mistaken Self, (3) Bystander Damage, and (4) Autoreactive B cells infected with EBV.

Conclusion

Given the infectious nature of EBV and its ability to elude the immune system, EBV emerges as a strong candidate for being the underlying cause of MS. The development of an EBV vaccine holds promise for preventing MS; however, overcoming the challenge of creating a safe and efficacious vaccine presents a significant obstacle.

A phase 2a open-label clinical trial to determine the effect of famciclovir on EBV activity as measured by EBV shedding in the saliva of patients with multiple sclerosis

BACKGROUND

Despite increasing evidence that Epstein-Barr virus (EBV) plays a causal role in MS, no treatments have been shown to reduce EBV turnover. We studied the effect of famciclovir on salivary EBV shedding in people with MS (NCT05283551) in a pilot, proof-of-concept study.

METHODS

People with MS receiving natalizumab provided weekly saliva samples for 12 weeks before starting famciclovir 500 mg twice daily for 12 weeks. Twelve saliva samples were provided on treatment and 12 following treatment. A real-time qPCR Taqman assay was used to detect EBV DNA in saliva. The proportion of saliva samples containing EBV DNA was compared using the Friedman test.

RESULTS

Of 30 participants (19 F; mean age 41 years; median EDSS 3.5), 29 received famciclovir, and 24 completed the 12-week course. Twenty-one participants provided at least one usable saliva sample in all epochs. Ten of the 21 had shedding in at least one sample pre-drug; 7/21 when taking famciclovir (not significant). No difference in EBV DNA copy number was seen. There were no drug-related serious adverse events.

CONCLUSION

No significant effect of famciclovir on EBV shedding was seen in this small pilot study. Given the low numbers, a small effect of famciclovir cannot be excluded. Salivary EBV shedding in this natalizumab-treated cohort was lower than in previous studies, which requires replication.

From Animal Models to Clinical Trials: The Potential of Antimicrobials in Multiple Sclerosis Treatment

Multiple sclerosis (MS) is a chronic, autoimmune, demyelinating disease of the central nervous system (CNS). Microbes, including bacteria and certain viruses, particularly Epstein-Barr virus (EBV), have been linked to the pathogenesis of MS. While there is currently no cure for MS, antibiotics and antivirals have been studied as potential treatment options due to their immunomodulatory ability that results in the regulation of the immune process. The current issue addressed in this systematic review is the effect of antimicrobials, including antibiotics, antivirals, and antiparasitic agents in animals and humans. We performed a comprehensive search of PubMed, Google Scholar, and Scopus for articles on antimicrobials in experimental autoimmune encephalomyelitis animal models of MS, as well as in people with MS (pwMS). In animal models, antibiotics tested included beta-lactams, minocycline, rapamycin, macrolides, and doxycycline. Antivirals included acyclovir, valacyclovir, and ganciclovir. Hydroxychloroquine was the only antiparasitic that was tested. In pwMS, we identified a total of 24 studies, 17 of them relevant to antibiotics, 6 to antivirals, and 1 relevant to antiparasitic hydroxychloroquine. While the effect of antimicrobials in animal models was promising, only minocycline and hydroxychloroquine improved outcome measures in pwMS. No favorable effect of the antivirals in humans has been observed yet. The number and size of clinical trials testing antimicrobials have been limited. Large, multicenter, well-designed studies are needed to further evaluate the effect of antimicrobials in MS.

Epstein-Barr virus as a cause of multiple sclerosis: opportunities for prevention and therapy

Multiple sclerosis is a chronic inflammatory disease of the CNS that results from the interplay between heritable and environmental factors. Mounting evidence from different fields of research supports the pivotal role of the Epstein-Barr virus (EBV) in the development of multiple sclerosis. However, translating this knowledge into clinically actionable information requires a better understanding of the mechanisms linking EBV to pathophysiology. Ongoing research is trying to clarify whether EBV causes neuroinflammation via autoimmunity or antiviral immunity, and if the interaction of EBV with genetic susceptibility to multiple sclerosis can explain why a ubiquitous virus promotes immune dysfunction in susceptible individuals. If EBV also has a role in driving disease activity, the characterisation of this role will help diagnosis, prognosis, and treatment in people with multiple sclerosis. Ongoing clinical trials targeting EBV and new anti-EBV vaccines provide hope for future treatments and preventive interventions.

Epstein-Barr virus and multiple sclerosis: moving from questions of association to questions of mechanism

The link between Epstein-Barr virus (EBV) and multiple sclerosis (MS) has puzzled researchers since it was first discovered over 40 years ago. Until that point, EBV was primarily viewed as a cancer-causing agent, but the culmination of evidence now shows that EBV has a pivotal role in development of MS. Early MS disease is characterised by episodic neuroinflammation and focal lesions in the central nervous system (CNS) that over time develop into progressive neurodegeneration and disability. Risk of MS is vanishingly low in EBV seronegative individuals, history of infectious mononucleosis (acute symptomatic primary infection with EBV) significantly increases risk and elevated antibody titres directed against EBV antigens are well-characterised in patients. However, the underlying mechanism - or mechanisms - responsible for this interplay remains to be fully elucidated; how does EBV-induced immune dysregulation either trigger or drive MS in susceptible individuals? Furthermore, deep understanding of virological and immunological events during primary infection and long-term persistence in B cells will help to answer the many questions that remain regarding MS pathogenesis. This review discusses the current evidence and mechanisms surrounding EBV and MS, which have important implications for the future of MS therapies and prevention.

Mendelian Randomization Analysis Suggests No Associations of Herpes Simplex Virus Infections With Multiple Sclerosis

Previous studies have suggested an association between infection with herpes simplex virus (HSV) and liability to multiple sclerosis (MS), but it remains largely unknown whether the effect is causal. We performed a two-sample Mendelian randomization (MR) study to explore the relationship between genetically predicted HSV infection and MS risk. Genetic instrumental variables for diagnosed infections with HSV (p < 5 × 10^–6) were retrieved from the FinnGen study, and single nucleotide polymorphisms associated with circulating immunoglobulin G (IgG) levels of HSV-1 and HSV-2 and corresponding summary-level statistics of MS were obtained from genome-wide association studies of the European-ancestry. Inverse-variance weighted MR was employed as the primary method and multiple sensitivity analyses were performed. Genetically proxied infection with HSV was not associated with the risk of MS (odds ratio [OR], 0.96; 95% confidence interval [CI], 0.90–1.02; p = 0.22) per one-unit increase in log-OR of herpes viral infections. MR results provided no evidence for the relationship between circulating HSV-1 IgG levels and MS risks (OR = 0.91; 95% CI, 0.81–1.03; p = 0.37), and suggested no causal effect of HSV-2 IgG (OR = 1.04; 95% CI, 0.96–1.13; p = 0.32). Additional sensitivity analyses confirmed the robustness of these null findings. The MR study did not support the causal relationship between genetic susceptibly to HSV and MS in the European population. Further studies are still warranted to provide informative knowledge, and triangulating evidence across multiple lines of evidence are necessary to plan interventions for the treatment and prevention of MS.

The Neuroimmunology of Multiple Sclerosis: Fictions and Facts

There have been tremendous advances in the neuroimmunology of multiple sclerosis over the past five decades, which have led to improved diagnosis and therapy in the clinic. However, further advances must take into account an understanding of some of the complex issues in the field, particularly an appreciation of "facts" and "fiction." Not surprisingly given the incredible complexity of both the nervous and immune systems, our understanding of the basic biology of the disease is very incomplete. This lack of understanding has led to many controversies in the field. This review identifies some of these controversies and facts/fictions with relation to the basic neuroimmunology of the disease (cells and molecules), and important clinical issues. Fortunately, the field is in a healthy transition from excessive reliance on animal models to a broader understanding of the disease in humans, which will likely lead to many improved treatments especially of the neurodegeneration in multiple sclerosis (MS).

Role of Increased Syncytin-1 Expression in Pathogenesis of Anti-N-Methyl-d-Aspartate Receptor Encephalitis

PURPOSE

Syncytin-1 may play a role in several neuropsychiatric disorders, but its function in anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is unknown. The purpose of this study was to examine the possible mechanism of action of syncytin-1 in patients with anti-NMDAR encephalitis.

PATIENTS AND METHODS

Twenty patients with anti-NMDAR encephalitis and eight controls were recruited. The protein levels of syncytin-1 in serum were determined using an enzyme-linked immunosorbent assay, and the transcript levels of syncytin-1 were determined using real-time quantitative PCR. Flow cytometry was used for peripheral blood lymphocyte subset detection. Further, the relationship between syncytin-1 levels and clinical features of anti-NMDAR encephalitis and peripheral blood lymphocyte subsets was analyzed.

RESULTS

Compared with those in controls, higher syncytin-1 levels and percentage of B cells (CD3-CD19+) were observed in patients with anti-NMDAR encephalitis. Among anti-NMDAR encephalitis patients, the level of syncytin-1 positively correlated with the proportion of B cells and modified Rankin scale score at onset and after immunotherapy and negatively correlated with the proportion of CD3+ T cells.

CONCLUSION

An increased expression of Syncytin-1 is associated with the pathogenesis of anti-NMDAR encephalitis, providing evidence for elucidating the pathogenesis of the disease and suggesting novel therapeutic targets. Further, this study clarifies the role of syncytin-1 in neuroimmune disorders.

Non-infectious mechanisms of neurological damage due to infection

Infections of the nervous system is a growing aspect of clinical neurology. Accumulating knowledge in early diagnosis, course, therapy and prognosis is enlarging the clinical tools required for effective therapy. Of special importance is the ability to differentiate between proper infections, where anti-microbial agents, when available, should be introduced and used and post infectious conditions where therapy is mainly directed against the host immune system. The two conditions sometimes overlap, a situation that requires the ability to combine clinical skills with the use of laboratory tools such as polymerase chain reaction (PCR), serology, and antigenic detection. In the era of the SARS-CoV-2 pandemic, the need to make this distinction is emphasized as correct diagnosis of post infectious conditions and expedited therapy is important and sometimes lifesaving. We here attempt to present several infectious agents and their possible indirect damage to the nervous system causing in some cases significant neurological deficits. We try to limit our focus on those mechanisms which do not involve the direct tissue damage by the infectious agents but rather are connected to para- and post-infectious mechanisms. We attempt to delineate the features that will enable to tailor the correct diagnosis and following the effective therapy.

The CD8 T Cell-Epstein-Barr Virus-B Cell Trialogue: A Central Issue in Multiple Sclerosis Pathogenesis

The cause and the pathogenic mechanisms leading to multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system (CNS), are still under scrutiny. During the last decade, awareness has increased that multiple genetic and environmental factors act in concert to modulate MS risk. Likewise, the landscape of cells of the adaptive immune system that are believed to play a role in MS immunopathogenesis has expanded by including not only CD4 T helper cells but also cytotoxic CD8 T cells and B cells. Once the key cellular players are identified, the main challenge is to define precisely how they act and interact to induce neuroinflammation and the neurodegenerative cascade in MS. CD8 T cells have been implicated in MS pathogenesis since the 80's when it was shown that CD8 T cells predominate in MS brain lesions. Interest in the role of CD8 T cells in MS was revived in 2000 and the years thereafter by studies showing that CNS-recruited CD8 T cells are clonally expanded and have a memory effector phenotype indicating in situ antigen-driven reactivation. The association of certain MHC class I alleles with MS genetic risk implicates CD8 T cells in disease pathogenesis. Moreover, experimental studies have highlighted the detrimental effects of CD8 T cell activation on neural cells. While the antigens responsible for T cell recruitment and activation in the CNS remain elusive, the high efficacy of B-cell depleting drugs in MS and a growing number of studies implicate B cells and Epstein-Barr virus (EBV), a B-lymphotropic herpesvirus that is strongly associated with MS, in the activation of pathogenic T cells. This article reviews the results of human studies that have contributed to elucidate the role of CD8 T cells in MS immunopathogenesis, and discusses them in light of current understanding of autoreactivity, B-cell and EBV involvement in MS, and mechanism of action of different MS treatments. Based on the available evidences, an immunopathological model of MS is proposed that entails a persistent EBV infection of CNS-infiltrating B cells as the target of a dysregulated cytotoxic CD8 T cell response causing CNS tissue damage.

Unbiased examination of genome-wide human endogenous retrovirus transcripts in MS brain lesions

BACKGROUND

Human endogenous retrovirus (HERV) expression in multiple sclerosis (MS) brain lesions may contribute to chronic inflammation, but expression of genome-wide HERVs in different MS lesions is unknown.

OBJECTIVE

We examined the HERV expression landscape in different MS lesions compared to control brains.

METHODS

Transcripts from 71 MS brain samples and 25 control WM were obtained by next-generation RNA sequencing and mapped against HERV transcripts across the human genome. Differential expression of mapped HERV-W and HERV-H reads between MS lesion types and controls was analysed.

RESULTS

Out of 6.38 billion high-quality paired end reads, 174 million reads (2.73%) mapped to HERV transcripts. There was no difference in HERVs expression level between MS and control brains, but HERV-W transcripts were significantly reduced in chronic active lesions. Of the four HERV-W transcripts exclusively present in MS, ERV3633503 located on chromosome 7q21.13 close to the MS genetic risk locus had the highest number of reads. In the HERV-H family, 75% of transcripts located to nearby 7q21-22 were overrepresented in MS, and ERV3643914 was expressed more than 16 times in MS compared to control brains.

CONCLUSION

Novel HERV-W and HERV-H transcripts located at chromosome 7 regions were uniquely expressed in MS lesions, indicating their potential role in brain lesion evolution.

Cannabidiol for Viral Diseases: Hype or Hope?

Background: The possibility of cannabidiol (CBD) to be used as an antiviral or to treat viral diseases has received limited attention so far, despite the growing number of claims that CBD could be used for the treatment of viral infection-related conditions. Aim and Methods: Therefore, we systematically retrieved and critically evaluated the scientific literature available on PubMed and the claims on the Internet, to assess the current state of knowledge on the use of CBD in viral diseases, and to provide suggestions for future research directions. Results: PubMed search referenced two original articles supporting the use of CBD for the treatment of hepatitis C and Kaposi sarcoma and one article reporting the ability of CBD to reduce neuroinflammation in a virus-induced animal model of multiple sclerosis. Internet search found 25 websites claiming more indications for CBD. Remarkably, those claims were provided mostly by commercial websites and were not supported by appropriate scientific references. Conclusion: Although preclinical studies suggest the potential effectiveness of CBD in viral diseases such as hepatitis C and Kaposi sarcoma, clinical evidence is still lacking. Anecdotal experiences of CBD use retrieved on the Internet, on the other side, lack any support from sound scientific evidence, although they might in some cases provide suggestions for conditions associated with viral infections that may deserve proper assessment in well-designed clinical trials.

Epstein-Barr Virus in Multiple Sclerosis: Theory and Emerging Immunotherapies

New treatments for multiple sclerosis (MS) focused on B cells have created an atmosphere of excitement in the MS community. B cells are now known to play a major role in disease, demonstrated by the highly impactful effect of a B cell-depleting antibody on controlling MS. The idea that a virus may play a role in the development of MS has a long history and is supported mostly by studies demonstrating a link between B cell-tropic Epstein–Barr virus (EBV) and disease onset. Efforts to develop antiviral strategies for treating MS are underway. Although gaps remain in our understanding of the etiology of MS, the role, if any, of viruses in propagating pathogenic immune responses deserves attention.

Epstein-Barr Virus-Specific CD8 T Cells Selectively Infiltrate the Brain in Multiple Sclerosis and Interact Locally with Virus-Infected Cells: Clue for a Virus-Driven Immunopathological Mechanism

EBV establishes a lifelong and asymptomatic infection in most individuals and more rarely causes infectious mononucleosis and malignancies, like lymphomas. The virus is also strongly associated with MS, a chronic neuroinflammatory disease with unknown etiology. Infectious mononucleosis increases the risk of developing MS, and immune reactivity toward EBV is higher in persons with MS, indicating inadequate control of the virus. Previous studies have suggested that persistent EBV infection in the CNS stimulates an immunopathological response, causing bystander neural cell damage. To verify this, we need to identify the immune culprits responsible for the detrimental antiviral response in the CNS. In this study, we analyzed postmortem brains donated by persons with MS and show that CD8 cytotoxic T cells recognizing EBV enter the brain and interact locally with the virus-infected cells. This antiviral CD8 T cell-mediated immune response likely contributes to MS pathology.

Epstein-Barr virus (EBV) is a ubiquitous herpesvirus strongly associated with multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system (CNS). However, the mechanisms linking EBV infection to MS pathology are uncertain. Neuropathological and immunological studies suggest that a persistent EBV infection in the CNS can stimulate a CD8 T-cell response aimed at clearing the virus but inadvertently causing CNS injury. Inasmuch as in situ demonstration of EBV-specific CD8 T cells and their effector function is missing, we searched for EBV-specific CD8 T cells in MS brain tissue using the pentamer technique. Postmortem brain samples from 12 donors with progressive MS and known HLA class I genotype were analyzed. Brain sections were stained with HLA-matched pentamers coupled with immunogenic peptides from EBV-encoded proteins, control virus (cytomegalovirus and influenza A virus) proteins, and myelin basic protein. CD8 T cells recognizing proteins expressed in the latent and lytic phases of the EBV life cycle were visualized in white matter lesions and/or meninges of 11/12 MS donors. The fraction (median value) of CD8 T cells recognizing individual EBV epitopes ranged from 0.5 to 2.5% of CNS-infiltrating CD8 T cells. Cytomegalovirus-specific CD8 T cells were detected at a lower frequency (≤0.3%) in brain sections from 4/12 MS donors. CNS-infiltrating EBV-specific CD8 T cells were CD107a positive, suggesting a cytotoxic phenotype, and stuck to EBV-infected cells. Together with local EBV dysregulation, selective enrichment of EBV-specific CD8 T cells in the MS brain supports the notion that skewed immune responses toward EBV contribute to inflammation causing CNS injury.

IMPORTANCE EBV establishes a lifelong and asymptomatic infection in most individuals and more rarely causes infectious mononucleosis and malignancies, like lymphomas. The virus is also strongly associated with MS, a chronic neuroinflammatory disease with unknown etiology. Infectious mononucleosis increases the risk of developing MS, and immune reactivity toward EBV is higher in persons with MS, indicating inadequate control of the virus. Previous studies have suggested that persistent EBV infection in the CNS stimulates an immunopathological response, causing bystander neural cell damage. To verify this, we need to identify the immune culprits responsible for the detrimental antiviral response in the CNS. In this study, we analyzed postmortem brains donated by persons with MS and show that CD8 cytotoxic T cells recognizing EBV enter the brain and interact locally with the virus-infected cells. This antiviral CD8 T cell-mediated immune response likely contributes to MS pathology.

Amidic derivatives of valproic acid, valpromide and valnoctamide, inhibit HSV-1 infection in oligodendrocytes

Herpes simplex virus type 1 (HSV-1) is a ubiquitous infectious agent that can establish latency in neurons, and in some cases, viral retrograde transport results in infection of the central nervous system (CNS). Several antivirals have been identified with the ability to inhibit HSV-1 replication in human cells to a greater or lesser degree, most of which are nucleoside analogues that unfortunately exhibit teratogenic potential, embryotoxicity, carcinogenic or antiproliferative activities and resistances in immunocompromised patients, specially. In the present study, we assessed two amidic derivatives of valproic acid (VPA) - valpromide (VPD) and valnoctamide (VCD) - which are already used in clinic treatments, as feasible HSV-1 antivirals in glial cells. Both VPD and VCD have exhibited increased efficacy in bipolar disorders and as anticonvulsant drugs compared to VPA, while being less teratogenic and hepatotoxic. Cytotoxicity assays carried out in our laboratory showed that VPD and VCD were not toxic in a human oligodendroglioma cell line (HOG), at least at the concentrations established for human treatments. Infectivity assays showed a significant inhibition of HSV-1 infection in HOG cells after VPD and VCD treatment, being more pronounced in VPD-treated cells, comparable to the effects obtained with acyclovir. Furthermore, the same antiherpetic effects of VPD were observed in other oligodendrocytic cell lines and rat primary oligodendrocytes (OPCs), confirming the results obtained in HOG cells. Altogether, our results allow us to propose VPD as a potential antiherpetic drug that is able to act directly on oligodendrocytes of the CNS.

Pharmacotherapy in Secondary Progressive Multiple Sclerosis: An Overview

Multiple sclerosis is an immune-mediated inflammatory disease of the central nervous system characterised by demyelination, neuroaxonal loss and a heterogeneous clinical course. Multiple sclerosis presents with different phenotypes, most commonly a relapsing-remitting course and, less frequently, a progressive accumulation of disability from disease onset (primary progressive multiple sclerosis). The majority of people with relapsing-remitting multiple sclerosis, after a variable time, switch to a stage characterised by gradual neurological worsening known as secondary progressive multiple sclerosis. We have a limited understanding of the mechanisms underlying multiple sclerosis, and it is believed that multiple genetic, environmental and endogenous factors are elements driving inflammation and ultimately neurodegeneration. Axonal loss and grey matter damage have been regarded as amongst the leading causes of irreversible neurological disability in the progressive stages. There are over a dozen disease-modifying therapies currently licenced for relapsing-remitting multiple sclerosis, but none of these has provided evidence of effectiveness in secondary progressive multiple sclerosis. Recently, there has been some early modest success with siponimod in secondary progressive multiple sclerosis and ocrelizumab in primary progressive multiple sclerosis. Finding treatments to delay or prevent the courses of secondary progressive multiple sclerosis is an unmet and essential goal of the research in multiple sclerosis. In this review, we discuss new findings regarding drugs with immunomodulatory, neuroprotective or regenerative properties and possible treatment strategies for secondary progressive multiple sclerosis. We examine the field broadly to include trials where participants have progressive or relapsing phenotypes. We summarise the most relevant results from newer investigations from phase II and III randomised controlled trials over the past decade, with particular attention to the last 5 years.