CAR T-cell therapy is an experimental treatment being tested in people with multiple sclerosis, particularly those whose disease has progressed despite standard medications. The approach borrows from cancer medicine: a patient’s own immune cells are removed, genetically reprogrammed to hunt down specific targets, and infused back into the body. In MS, those targets are B cells, a type of immune cell now understood to play a central role in driving the disease. As of mid-2025, six clinical trials are underway, and the earliest case reports show signs of B-cell depletion inside the brain and spinal cord, something existing drugs struggle to achieve.
Why B Cells Became the Focus in MS
For decades, MS was understood primarily as a T-cell disease, with the immune system’s T cells attacking the protective myelin coating around nerves. That picture has shifted. B cells contribute to MS through several routes beyond just producing antibodies. They present fragments of myelin to T cells, essentially flagging the nervous system as a target, and they secrete signaling molecules that can amplify or dampen inflammation.1PubMed Central. The role of B cells in the immunopathogenesis of multiple sclerosis The importance of B cells was underscored when drugs like rituximab and ocrelizumab, which wipe out B cells in the bloodstream, showed striking results in clinical trials for relapsing-remitting MS.2PubMed Central. Evidence for the role of B cells and immunoglobulins in the pathogenesis of multiple sclerosis
But those drugs have a limitation that matters a great deal for people with progressive MS. Monoclonal antibodies are large molecules that do not easily cross the blood-brain barrier, so they are effective at clearing B cells from the blood and peripheral tissues but leave behind B cells and related cells that have already taken up residence inside the central nervous system. In progressive MS, chronic inflammation driven by immune cells already compartmentalized within the brain and spinal cord is thought to be a key driver of ongoing nerve damage. Standard infusion therapies can slow relapses but often fail to halt the slow, grinding disability accumulation that defines the progressive phase of the disease.
How CAR T Cells Differ from Existing Drugs
The core appeal of CAR T-cell therapy for MS is reach. Unlike antibody-based drugs, CAR T cells are living cells that can migrate into tissues, including the central nervous system. In preclinical work, anti-CD19 CAR T cells thoroughly depleted B cells not only in peripheral tissues but also within the CNS of treated animals.3PubMed Central. CAR-T Cell-Mediated B-Cell Depletion in Central Nervous System Autoimmunity Early clinical data in MS patients confirm that CAR T cells can traffic into the cerebrospinal fluid and expand there, depleting pathogenic B cells inside the nervous system in a way that circulating antibodies cannot match.4PubMed. CAR T cells for multiple sclerosis: Engineering T cells to disrupt chronic B cell-driven neuroinflammation
There is also a durability argument. Monoclonal antibodies wear off as they are cleared from the body, requiring repeated infusions every few months for years, sometimes indefinitely. CAR T cells, by contrast, can persist in the body for weeks to months and potentially reset the immune system in a more lasting way. Whether that durability translates into sustained benefit for MS remains an open question, but the theoretical advantage is clear: one infusion might accomplish what years of repeat infusions struggle to achieve.
What the Earliest Patient Data Show
The clinical evidence in MS is still very early, drawn from single-digit patient numbers, but the signals are worth understanding. The first published case report of progressive MS treated with CAR T-cell therapy involved two patients who received KYV-101, an anti-CD19 CAR T product. Both showed clinical symptom improvement, including increased walking distance. In the cerebrospinal fluid, researchers found a significant decrease in antibody levels and confirmed that CAR T cells had expanded inside the CNS. Neither patient developed ICANS, a neurological complication commonly feared with CAR T therapy.5PubMed Central. CAR-T cell therapy: A new dawn in the treatment of autoimmune disease
A separate study reported on two MS patients treated with CD19-targeting CAR T cells. In one patient, circulating B cells were depleted by day two and had not returned by day 100. The number of oligoclonal bands in cerebrospinal fluid, a hallmark of intrathecal immune activity in MS, dropped from 13 to 6 and stayed reduced through day 64. The second patient, who had no detectable circulating B cells at baseline (likely because of prior ocrelizumab treatment), did not show the same changes in oligoclonal bands.6Med. CD19-targeted chimeric antigen receptor T cell therapy in two patients with multiple sclerosis That divergence hints at something important: outcomes may depend on each patient’s residual disease biology at the time of treatment.
A larger report examined four patients with refractory MS who received KYV-101 after a conditioning regimen of fludarabine and cyclophosphamide. Three of the four experienced mild cytokine release syndrome (grade 1) that required treatment with anti-inflammatory medications. One patient had opioid-resistant headaches raising suspicion of low-grade ICANS. All four had temporary liver enzyme elevations, and low white blood cell counts requiring growth factor support were observed across the group.7Blood. CD19-Directed CAR T Cell Therapy in 4 Patients with Refractory Multiple Sclerosis These side effects were manageable, though the numbers are far too small to draw broad safety conclusions.
CD19, BCMA, and Dual-Target Approaches
Most MS trials so far use CAR T cells aimed at CD19, a protein found on the surface of most B cells. CD19 is the same target used in approved CAR T products for blood cancers, so there is substantial safety experience with this approach. But CD19 has a blind spot: plasma cells, the fully mature B cells that pump out antibodies, often lose CD19 expression. If pathogenic antibody-producing plasma cells within the CNS are part of what drives progressive MS, a CD19-only approach might miss them.
That gap motivated researchers to try targeting BCMA (B-cell maturation antigen), a protein expressed on plasma cells. A phase 1 trial treated five patients with progressive MS using anti-BCMA CAR T cells. The investigators detected plasma cell depletion within the CNS, prolonged CAR T-cell expansion in the cerebrospinal fluid, and signs that microglial activation (a marker of brain inflammation) was reduced.8PubMed. Anti-BCMA CAR-T therapy in patients with progressive multiple sclerosis Microglial calming is a particularly intriguing finding, since activated microglia are implicated in the smoldering inflammation that characterizes progressive disease.
A logical next step is combining both targets. AstraZeneca’s ZENITH trial, a phase 1b study, is evaluating AZD0120, an autologous CAR T product that targets both CD19 and BCMA, in adults with refractory relapsing or progressive MS.9AstraZeneca Clinical Trials. An open-label study of AZD0120 in adults with multiple sclerosis – ZENITH The theory is that hitting both targets simultaneously could clear a broader spectrum of pathogenic B cells and plasma cells than either target alone. Results from studies of dual-targeting CAR T cells in lupus have been encouraging, and researchers have suggested similar approaches could be explored for MS.10Molecular Therapy. CAR T-Cell Therapy for Multiple Sclerosis: What to Know
Safety Concerns and What Is Different About Autoimmune Patients
In oncology, CAR T therapy is associated with some serious complications, particularly cytokine release syndrome and ICANS. CRS happens when the newly activated CAR T cells trigger a massive inflammatory response, causing fever, low blood pressure, and in severe cases, organ dysfunction. ICANS involves neurological symptoms ranging from confusion to seizures. Both are well-documented risks in cancer patients.
There are reasons to expect autoimmune patients may fare better. People with MS and other autoimmune conditions lack the large masses of malignant cells that can fuel intense immune reactions during CAR T therapy, and early experience supports the idea that toxicity tends to be lower grade and manageable with standard treatments.11PubMed Central. Chimeric antigen receptor T cell therapy for autoimmune disease In the MS cases reported so far, CRS has been grade 1 in most patients, and ICANS has been absent or suspected at the mildest level. That said, MS introduces a unique concern: any inflammatory event happening inside a brain already damaged by disease raises the question of whether even mild ICANS could worsen existing neurological deficits. Longer follow-up in more patients is needed to understand that risk.
A separate, slower-burning safety issue is hypogammaglobulinemia, a sustained drop in antibody levels that follows the deep depletion of B cells. Since B cells are responsible for producing antibodies, wiping them out can leave a person more vulnerable to infections. Data from cancer patients treated with CD19-targeting CAR T cells found that hypogammaglobulinemia after treatment was associated with roughly a 2.7-fold increased risk of serious infection.12PubMed Central. Association of CD19+-Targeted Chimeric Antigen Receptor (CAR) T-cell Therapy with Hypogammaglobulinemia, Infection and Mortality In a study of patients receiving BCMA-targeting CAR T therapy, about 30 percent developed a severe infection, and moderate to severe hypogammaglobulinemia persisted beyond one year in roughly two-thirds of patients.13PubMed Central. Characterization of Hypogammaglobulinemia, Infection Incidence, and Mortality in Patients Receiving B-cell Maturation Antigen Chimeric Antigen Receptor (CAR) T-cell Therapy These figures come from cancer populations, many of whom were already immunocompromised by prior chemotherapy, so they may overstate the risk for otherwise healthier autoimmune patients. Still, the concern is real and will need close monitoring in MS trials.
Who Is Currently Eligible for Trials
If you have MS and are reading this wondering whether you could enroll in a trial, the eligibility criteria are fairly specific. The KYV-101 trial, for instance, requires a diagnosis of primary or secondary progressive MS, an age between 25 and 70, a disability score (EDSS) between 3 and 7, evidence of clinical worsening within the prior two years, and adequate organ function with no active infections or major comorbidities.14Blood. A Study of Kyv-101, a CD19 CAR T Cell Therapy, in Participants with Treatment Refractory Progressive Multiple Sclerosis In practical terms, that means the trials are aimed at people with moderate disability who are clearly getting worse despite available treatments, not at those newly diagnosed or with mild disease.
The EDSS range of 3 to 7 translates roughly to someone who can still walk (at minimum with bilateral assistance) but has meaningful functional limitations. Patients with very advanced disability (wheelchair-bound, EDSS above 7) or very mild disease (EDSS below 3) are not being enrolled in these early studies. The logic is pragmatic: researchers want patients sick enough that the risk-benefit calculus favors an aggressive experimental therapy, but not so advanced that irreversible nerve damage makes it impossible to detect improvement.
Next-Generation Approaches on the Horizon
While the current trials use conventional CAR T cells that kill B cells, several next-generation strategies are being developed that could change the treatment’s profile substantially.
One approach flips the script entirely. Instead of using killer T cells, researchers are engineering regulatory T cells (Tregs) with CARs. Tregs are the immune system’s peacekeepers, the cells responsible for calming down overactive immune responses. By equipping Tregs with a receptor that recognizes myelin oligodendrocyte glycoprotein (MOG), a protein on the surface of myelin, scientists have created cells that home in on the site of damage in the nervous system and actively suppress the autoimmune attack rather than just eliminating B cells.15PubMed Central. MOG-specific CAR Tregs: a novel approach to treat multiple sclerosis In animal models of MS, these engineered CAR-Tregs suppressed disease progression.16PubMed. Engineered regulatory T cells expressing myelin-specific chimeric antigen receptors suppress EAE progression This is still preclinical work, but the concept of restoring immune tolerance rather than depleting immune cells is appealing because it could potentially address the root cause of MS without the prolonged immunosuppression that comes with B-cell depletion.
Another innovation targets the manufacturing bottleneck. Current CAR T therapy is autologous, meaning each patient’s cells must be individually harvested, shipped to a manufacturing facility, genetically modified, expanded, and shipped back. This takes weeks, is enormously expensive, and ties every treatment to one patient. Allogeneic (donor-derived) CAR T cells could solve that problem. In a recent study, allogeneic anti-CD19 CAR T cells from healthy donors were used for the first time in patients with autoimmune diseases. The advantage is twofold: donor T cells are not weakened by years of immunosuppressive drugs the way a patient’s own cells might be, and there is no risk of accidentally modifying one of the patient’s own autoreactive T-cell clones.17Handbook of Clinical Neurology. The future unfolded: CAR T cells and the transformation of treatment algorithms in autoimmune neurology
Perhaps the most ambitious idea is eliminating the need for a manufacturing facility altogether. Researchers are developing lipid nanoparticles loaded with mRNA that can reprogram T cells directly inside the body, skipping the entire ex vivo manufacturing step.18PubMed. In vivo CAR T cell generation to treat cancer and autoimmune disease This in vivo approach would produce CAR T cells that are transient by design, since the mRNA degrades within days and the CAR expression fades, so the immune modification is temporary and reversible. For autoimmune diseases, where the safety bar is higher than in cancer because patients are not facing an immediately life-threatening illness, the ability to control how long the therapy lasts is attractive.19RMD Open. CAR T cells for treating autoimmune diseases Repeat doses could be given as needed, making the treatment more like a drug course than a one-time bet.
What the Autoimmune Disease Experience Tells Us
MS is not the first autoimmune disease to be treated with CAR T cells. Lupus was the trailblazer. A case series followed patients with severe lupus, inflammatory myositis, and systemic sclerosis who received CD19-targeting CAR T cells. The treatment induced rapid, deep depletion of circulating B cells and led to drug-free remission in refractory cases.20PubMed. CD19 CAR T-Cell Therapy in Autoimmune Disease – A Case Series with Follow-up Strikingly, B cells eventually returned in these patients, but the reconstituted B-cell population appeared to be “reset,” no longer driving autoimmune attacks. Some patients have maintained remission for over two years without any immunosuppressive medication.21The Lancet. CAR T cells targeting B cells in autoimmune diseases
Whether that same immune reset can happen in MS is far from certain. Lupus is primarily a systemic disease, with the immune attack happening in accessible organs and the bloodstream. MS traps much of its pathology behind the blood-brain barrier, in a compartment that is harder to reach and harder to monitor. The early data showing CAR T cells expanding within the cerebrospinal fluid of MS patients are promising precisely because they suggest the cells can get to where they are needed, but whether the immune reset seen in lupus translates to a neurological disease with established nerve damage is a different question. Damaged nerve fibers do not regrow just because the immune attack stops. The hope is that halting the inflammatory process can prevent further damage and allow whatever compensatory repair the nervous system can manage, but reversing existing disability may be beyond what any immune therapy can accomplish alone.
The Conditioning Regimen and What It Means for Patients
Before CAR T cells are infused, patients undergo lymphodepletion, a short course of chemotherapy drugs designed to clear out existing immune cells and make room for the engineered cells to expand. In the MS trials reported so far, this has involved fludarabine and cyclophosphamide given over three days.7Blood. CD19-Directed CAR T Cell Therapy in 4 Patients with Refractory Multiple Sclerosis These are the same drugs used in cancer CAR T protocols, though sometimes at lower doses.
Lymphodepletion is not a trivial step. It temporarily wipes out much of the patient’s immune defense, causing low blood counts that can last weeks and require monitoring for infections. Neutropenia, a dangerously low level of infection-fighting white blood cells, occurred in the MS patients treated so far and required growth factor injections. For someone already living with a neurological disability, spending days in a hospital setting while immunosuppressed adds practical and medical complexity. Any future push to make CAR T therapy more accessible for MS will likely need to address whether lighter conditioning regimens or outpatient-friendly protocols are feasible.
Practical Realities of Cost and Access
In oncology, approved CAR T products carry list prices ranging from roughly $370,000 to over $500,000 per infusion, not counting hospitalization, conditioning chemotherapy, and follow-up care. The total cost of the treatment episode often exceeds $1 million. For cancer patients with no other options, insurers have gradually come around to covering these costs, but the economics remain a barrier.
For MS, the math gets harder. MS is far more common than the blood cancers currently treated with CAR T cells. If the therapy works and demand scales, the manufacturing infrastructure that barely keeps up with oncology volumes would face enormous strain. This is one reason the next-generation approaches, particularly allogeneic off-the-shelf products and in vivo reprogramming, matter so much. They could dramatically reduce per-patient costs by eliminating the bespoke manufacturing process that drives much of the current expense. Without those advances, CAR T therapy for MS would likely remain confined to the sickest patients at specialized academic centers, a boutique treatment rather than a broadly accessible one.
Timelines and Tempering Expectations
The current trials are phase 1 and phase 1b studies, which means their primary purpose is to establish safety and appropriate dosing, not to prove the therapy works. Efficacy endpoints like changes in disability scores and patient-reported outcomes are being tracked, but the trials are too small and too early to deliver definitive answers about whether CAR T therapy will meaningfully change the course of progressive MS. Based on typical drug development timelines, pivotal trials that could support regulatory approval are likely several years away, assuming the early data continue to look favorable.
For people living with progressive MS today, this timeline is both hopeful and frustrating. The unmet need is enormous. No currently approved therapy has shown a robust ability to reverse or even reliably slow disability accumulation in progressive MS. Ocrelizumab has a limited indication for primary progressive MS, but its benefit is modest and concentrated in younger patients with active inflammatory lesions. If CAR T therapy can penetrate the CNS, reset the immune system, and halt the compartmentalized inflammation that drives progressive disease, it would represent a genuine shift in what is possible. But those are big “ifs,” and the history of MS therapeutics is littered with approaches that looked promising in small studies but failed at scale. The responsible message is one of cautious optimism: the biological rationale is strong, the early signals are encouraging, and the path from here to a proven treatment still has a great deal of uncertainty in it.