Research into multiple sclerosis is advancing on several fronts simultaneously, from drugs that cross into the brain in ways older therapies couldn’t, to vaccines targeting a virus now strongly linked to the disease, to imaging tools that can spot smoldering damage years before it causes disability. Here’s where the most significant work stands right now.
Drugs That Reach the Brain Directly
Most current MS therapies work by suppressing or redirecting the immune system in the bloodstream. A newer class of drugs called BTK inhibitors is generating significant interest because these small molecules can cross the blood-brain barrier and act on immune cells inside the central nervous system itself. Four are now in Phase 3 clinical trials: evobrutinib, fenebrutinib, remibrutinib, and tolebrutinib.
These drugs block an enzyme that immune cells (particularly B cells and certain scavenger cells in the brain called microglia) need to activate. Three of the four bind to this enzyme permanently, shutting it down for good. Fenebrutinib works differently, binding reversibly so the enzyme can eventually resume function. The hope is that by calming immune activity inside the brain, these drugs will address the slow, grinding inflammation that current treatments often miss, especially in progressive forms of the disease.
Repairing Damaged Myelin
Every existing MS treatment focuses on preventing new damage. None can reverse what’s already happened. That makes remyelination, the process of regrowing the protective coating around nerve fibers, one of the most sought-after goals in MS research.
One of the furthest-along candidates is clemastine fumarate, an old over-the-counter antihistamine that was found to promote myelin repair in lab studies. UCSF is running clinical trials using advanced MRI to measure whether clemastine can produce detectable myelin regrowth in people with chronic demyelinating injuries. If it works, it would represent a fundamental shift in MS care, moving from damage prevention to actual restoration of nerve function.
The Epstein-Barr Virus Connection
A landmark 2022 study of 10 million military personnel found that infection with Epstein-Barr virus (EBV) increased the risk of developing MS 32-fold, making it the strongest environmental risk factor identified for the disease. This has opened an entirely new line of attack: preventing MS by preventing EBV infection in the first place.
Moderna is running a Phase 1/2 trial of an mRNA vaccine called mRNA-1189, designed to prevent EBV infection. The trial is testing the vaccine in healthy people aged 10 to 30, the age range when most EBV infections occur. It’s a prevention strategy rather than a treatment for existing MS, but if EBV truly is the trigger that sets the disease in motion, vaccinating young people could eventually reduce new MS cases dramatically. Researchers are also investigating whether targeting EBV in people who already have MS could slow or alter the disease course.
Blood Tests That Track Nerve Damage
One of the persistent challenges in MS care is measuring what’s actually happening inside the brain between MRI scans. A protein called neurofilament light chain (NfL) is changing that. When nerve fibers are injured, they release this structural protein into the spinal fluid and blood, making it a real-time indicator of how much damage is occurring.
In healthy people between ages 20 and 50, blood levels of NfL typically fall between 5 and 10 picograms per milliliter, rising more steeply after age 50 to 60. Elevated levels in someone with MS suggest active inflammation and neurodegeneration. Researchers are working to establish standardized thresholds that clinicians can use to gauge whether a treatment is working, whether the disease is quietly progressing, or whether a relapse is brewing before symptoms appear. Age is a significant factor in interpreting results, which has complicated efforts to set universal cutoffs.
Imaging Smoldering Inflammation
Standard MRI can show where MS lesions are, but it can’t easily distinguish between old scars and lesions that are still actively inflamed. Ultra-high-field 7-Tesla MRI is changing that by revealing what are called paramagnetic rim lesions (PRLs): brain lesions with a distinctive bright border caused by iron-laden inflammatory cells clustered at their edges.
These rim lesions are markers of “chronic active” inflammation, a slow-burn process where immune cells continue destroying tissue for months or years after the initial attack. Research published in the Journal of Clinical Investigation found that lesions with a persistent rim showed less healing over time and became darker on imaging, indicating ongoing tissue destruction. Larger lesions, those 162 cubic millimeters or bigger when a rim was already visible at baseline, were strongly predicted to remain chronically active at 12 months. This kind of imaging could help identify patients whose disease is smoldering beneath the surface and who need more aggressive treatment, even if they appear clinically stable.
Progress in Progressive MS
Relapsing-remitting MS has over 20 approved treatments. Progressive MS, where disability accumulates steadily without clear relapses, has far fewer options. Much of the current research pipeline is aimed at closing that gap.
Ocrelizumab remains the only therapy with specific approval for primary progressive MS, having received breakthrough therapy designation from the FDA. Beyond that, trials are exploring drugs with different mechanisms. Idebenone, a synthetic compound related to coenzyme Q10 that may protect mitochondria (the energy factories inside nerve cells), is in Phase 1/2 testing for primary progressive MS. The BTK inhibitors mentioned earlier are also being studied in progressive populations, since their ability to penetrate the brain makes them theoretically better suited to address the compartmentalized inflammation that drives progressive disease.
Stem Cell Transplantation
Autologous hematopoietic stem cell transplantation (HSCT) is the most aggressive treatment currently used for MS. It involves wiping out the immune system with chemotherapy and rebuilding it from the patient’s own stem cells. The goal is to reset the immune system so it stops attacking myelin.
Long-term data from a cohort of 281 patients followed for a median of 6.6 years showed a 5-year progression-free survival rate of 46%, meaning nearly half of patients had no measurable worsening over five years. Overall survival at five years was 93%. These numbers reflect the tradeoff: HSCT can produce durable remissions that no drug has matched, but it carries real risks from the intensive chemotherapy required. Research is now focused on identifying which patients benefit most (generally younger people with highly inflammatory relapsing disease) and on refining the transplant protocols to reduce toxicity.
Genetics and Risk Prediction
Genome-wide association studies have now identified 233 independent genetic risk locations linked to MS susceptibility. Of these, 32 sit within a region of the genome called the major histocompatibility complex, which plays a central role in how the immune system distinguishes “self” from “foreign.” The remaining 201 are scattered across the rest of the genome. No single gene causes MS, but the cumulative picture is helping researchers understand which immune pathways go wrong. This genetic mapping is also fueling efforts to build risk scores that could one day flag people at elevated risk before the disease begins, particularly in combination with EBV status and other environmental factors.
The Gut Microbiome’s Role
People with relapsing-remitting MS have a measurably different collection of gut bacteria compared to healthy individuals. Studies comparing 71 people with MS to 71 matched controls found that the MS group had higher levels of certain bacteria (notably Akkermansia muciniphila and Acinetobacter calcoaceticus) and lower levels of others (Parabacteroides distasonis). These aren’t random differences. Lab experiments showed that the bacteria enriched in MS patients promoted inflammatory immune responses, while the depleted species had anti-inflammatory effects.
Lower levels of bifidobacteria in MS patients have also been linked to higher concentrations of a key inflammatory molecule in both spinal fluid and blood. This line of research hasn’t yet produced a treatment, but it’s building the case that the gut microbiome actively shapes the immune dysfunction driving MS, potentially opening the door to probiotic or dietary interventions.
Fasting and Immune Regulation
Clinical trials of intermittent calorie restriction in people with MS have produced some intriguing immune changes. Participants on intermittent fasting protocols showed significant reductions in memory T cell subsets, particularly effector memory and Th1 cells, which are among the immune cells that drive MS attacks. At the same time, they showed increases in naïve T cells, which haven’t yet been programmed to attack. These shifts were not seen in people following standard daily calorie restriction or eating normally, suggesting something specific about the cycling pattern of intermittent fasting alters immune cell populations in ways relevant to MS. Participants who showed the biggest changes in certain fat-related blood markers also displayed the most notable T cell shifts, pointing to a connection between metabolic changes and immune regulation.