Stem Cell Therapy for Multiple Sclerosis: Current Trials and Evidence
At a Glance: Two stem cell approaches are being used for multiple sclerosis. Autologous hematopoietic stem cell transplant (HSCT) effectively “reboots” the immune system and has the strongest evidence, with some trials showing 70 to 80 percent of relapsing-remitting MS patients remaining relapse-free at 5 years. Mesenchymal stem cell (MSC) infusions offer a less aggressive option that may reduce inflammation and promote repair. HSCT carries real risks, including a treatment-related mortality rate of 0.3 to 1 percent in experienced centers. MSC therapy has a better safety profile but weaker evidence for durable benefit.
Multiple sclerosis is a disease where the immune system attacks the myelin sheath that insulates nerve fibers in the brain and spinal cord. Over time, this damage accumulates, causing progressive neurological disability. Standard disease-modifying therapies (DMTs) reduce relapse rates and slow progression, but they do not reverse existing damage, and a subset of patients continues to worsen despite aggressive treatment.
This is what makes stem cell therapy such a compelling area of research for MS. Two fundamentally different strategies are in use: one that wipes out and rebuilds the immune system (HSCT), and one that introduces repair-oriented cells to reduce inflammation and potentially promote remyelination (MSC therapy). Both have real data behind them, and both have real limitations.
HSCT: Autologous Hematopoietic Stem Cell Transplant
How HSCT Works
HSCT for MS follows a conceptually simple but medically intense process:
- Mobilization: Growth factors (typically G-CSF, with or without cyclophosphamide) are given to stimulate the bone marrow to release hematopoietic stem cells into the bloodstream.
- Collection: Stem cells are harvested from the blood through apheresis (a process similar to donating plasma).
- Conditioning (ablation): High-dose chemotherapy destroys the existing immune system. This is the most dangerous phase. Common regimens include BEAM (carmustine, etoposide, cytarabine, melphalan) or cyclophosphamide with ATG (anti-thymocyte globulin).
- Transplant: The harvested stem cells are infused back into the patient’s bloodstream. They migrate to the bone marrow and begin rebuilding a new immune system.
- Recovery: Over the following weeks to months, the new immune system gradually reconstitutes. During this period, the patient is severely immunocompromised and at risk for infections.
The theory behind HSCT is that the autoimmune process driving MS is contained within the mature immune cell population. By destroying those cells and allowing the immune system to rebuild from stem cells, the aberrant immune response is eliminated. The new immune system, in effect, does not “remember” to attack myelin.
Clinical Evidence for HSCT
HSCT for MS has accumulated substantial clinical evidence over the past two decades.
The MIST Trial (2019): This was the first randomized controlled trial comparing HSCT to standard disease-modifying therapy in relapsing-remitting MS (RRMS). Published in JAMA, the trial randomized 110 patients to HSCT or best available DMT. At a median follow-up of 3 years, the HSCT group showed dramatically better outcomes: the annualized relapse rate was 90 percent lower, disability progression occurred in only 2 of 55 HSCT patients versus 34 of 55 DMT patients, and MRI disease activity was nearly abolished in the HSCT group.
The HALT-MS Trial: This single-arm study followed 24 RRMS patients after HSCT for 5 years. Event-free survival (no relapses, no disability progression, no new MRI lesions) was 69.2 percent at 5 years. For a disease that typically continues to produce relapses and new lesions on treatment, this level of disease control is remarkable.
Swedish Registry Data: A large observational study from the Swedish MS Registry compared 174 HSCT patients to 1,823 patients on high-efficacy DMTs (natalizumab, rituximab, fingolimod). HSCT was associated with lower relapse rates and reduced disability progression over a median 5-year follow-up. Notably, the HSCT patients had more aggressive disease at baseline, making the favorable comparison even more striking.
Long-term follow-up data: Multiple cohorts have now reported 10-year outcomes. Approximately 60 to 70 percent of HSCT-treated RRMS patients remain free of relapses, disability progression, and new MRI activity at 10 years. Some patients have shown sustained improvement in disability scores, not just stabilization.
Key Point: HSCT works best in relapsing-remitting MS with active inflammatory disease. The evidence for progressive MS (both primary and secondary) is much weaker. In progressive disease, the pathology shifts from immune-mediated inflammation to neurodegeneration, which HSCT does not directly address.
Who Qualifies for HSCT
Patient selection is critical for both safety and efficacy. The best candidates share these characteristics:
- Relapsing-remitting MS (RRMS) with active inflammatory disease (relapses and/or new/enhancing MRI lesions)
- Failure of at least one high-efficacy DMT (or rapid, aggressive disease at onset)
- Age under 50 (outcomes decline with age, though this is not an absolute cutoff)
- Disease duration under 10 years (earlier treatment is associated with better outcomes)
- EDSS score under 6.0 (patients with less accumulated disability respond better)
- No significant comorbidities that would increase chemotherapy risk (cardiac disease, active infection, organ dysfunction)
Risks of HSCT
HSCT is not a casual treatment. It involves high-dose chemotherapy with real and serious risks.
| Risk | Details |
|---|---|
| Treatment-related mortality | 0.3 to 1 percent in experienced centers using modern protocols. Historical rates were higher (up to 5 percent in early studies) due to more aggressive conditioning regimens. |
| Infection | The most common serious complication. Patients are severely immunocompromised for weeks to months. Viral reactivation (especially herpes viruses) and bacterial infections are the primary concerns. |
| Infertility | Chemotherapy can cause permanent infertility, particularly with certain conditioning regimens. Fertility preservation should be discussed before treatment. |
| Secondary autoimmunity | Approximately 5 to 10 percent of HSCT patients develop a new autoimmune condition (most commonly thyroid disease) as the immune system reconstitutes. |
| Prolonged hospitalization | Typically 2 to 4 weeks inpatient, followed by months of restricted activity and infection precautions. |
| Late effects of chemotherapy | Small increased risk of secondary malignancies, cardiac effects, and other long-term chemotherapy side effects. |
Safety Note: Center experience matters enormously for HSCT outcomes. Mortality rates are significantly lower at transplant centers that perform HSCT for MS regularly versus those that do it infrequently. If you are considering HSCT, choose a center with a documented track record of at least 20 to 30 MS-specific transplants.
MSC Therapy: Mesenchymal Stem Cell Infusions
How MSC Therapy Works
Mesenchymal stem cells (MSCs) are multipotent cells found in bone marrow, adipose tissue, and umbilical cord tissue. Unlike HSCT, MSC therapy does not destroy the immune system. Instead, it introduces cells that have immunomodulatory and potentially neuroprotective properties.
MSCs work through several mechanisms relevant to MS:
- Immunomodulation: MSCs suppress overactive immune responses by shifting the balance from pro-inflammatory T-helper 1 and T-helper 17 cells toward regulatory T cells
- Anti-inflammatory effects: They secrete anti-inflammatory cytokines (IL-10, TGF-beta) and reduce pro-inflammatory signaling
- Neuroprotection: MSC-derived growth factors (BDNF, NGF) may protect neurons from ongoing damage
- Potential remyelination support: Laboratory studies suggest MSCs may promote oligodendrocyte precursor cell activity, which could support remyelination, though this has not been convincingly demonstrated in human MS patients
The MESEMS Trial
The MESEMS (Mesenchymal Stem Cells for Multiple Sclerosis) trial is the largest and most rigorous study of MSC therapy for MS conducted to date. This international, randomized, double-blind, crossover trial enrolled patients at nine centers across Europe, Canada, and the Middle East.
Patients received either a single intravenous infusion of autologous bone marrow-derived MSCs or placebo, then crossed over to the other treatment after 24 weeks. The primary endpoint was the number of gadolinium-enhancing MRI lesions.
Results published in 2024 showed a modest but statistically significant reduction in enhancing lesions in the MSC group. The treatment was well-tolerated with no serious adverse events attributable to the MSCs. However, clinical improvements (relapse rate, disability scores) did not reach statistical significance, suggesting that a single MSC infusion may not be sufficient for meaningful clinical benefit.
Other MSC Studies
Several smaller studies and case series have reported on MSC therapy for MS:
- A 2020 Israeli study of intrathecal (injected into the spinal fluid) MSC delivery in progressive MS patients showed some stabilization of disability and reduction in cerebrospinal fluid inflammatory markers
- Multiple small studies of repeated MSC infusions (3 to 6 sessions over 6 to 12 months) suggest that multiple doses may be more effective than single infusions
- Adipose-derived MSCs and umbilical cord-derived MSCs are being studied as alternatives to bone marrow-derived MSCs, with some data suggesting comparable or superior potency
RRMS vs. Progressive MS: Why It Matters
The distinction between relapsing-remitting and progressive MS is crucial when evaluating stem cell therapy options.
| MS Type | HSCT Evidence | MSC Evidence |
|---|---|---|
| Relapsing-remitting (RRMS) | Strong. 70 to 80 percent relapse-free at 5 years. Multiple RCTs support its use. | Modest. Single infusions show MRI improvement but limited clinical benefit. Repeat dosing may be more effective. |
| Secondary progressive (SPMS) | Mixed. Patients with active inflammation may benefit. Those without active inflammation show less response. | Limited data. Some stabilization reported in small studies. Intrathecal delivery may be more effective than IV. |
| Primary progressive (PPMS) | Weak. HSCT primarily targets immune-mediated inflammation, which is less prominent in PPMS. | Limited but ongoing research. PPMS may benefit from MSC neuroprotective properties, but evidence is early-stage. |
Active Clinical Trials
Several important trials are currently recruiting or reporting results:
- BEAT-MS (Best Available Therapy versus Autologous Hematopoietic Stem Cell Transplant for MS): A major NIH-funded randomized trial comparing HSCT to best available high-efficacy DMT. This trial is expected to provide definitive evidence on HSCT’s role relative to modern MS medications. Results are anticipated in the coming years.
- STAR-MS: A UK-based randomized trial comparing HSCT to alemtuzumab (one of the most potent DMTs) in aggressive RRMS. Results are anticipated soon.
- Multiple MSC trials: ClinicalTrials.gov lists over 30 active or recruiting MSC studies for MS, testing different cell sources, delivery routes, and dosing schedules.
- Exosome studies: Early-phase trials are beginning to explore MSC-derived exosomes for MS, which could provide immunomodulatory benefits without transplanting live cells.
You can search for current MS stem cell trials at ClinicalTrials.gov using search terms like “stem cell multiple sclerosis” or “HSCT multiple sclerosis.”
Cost and Access
HSCT
In the United States, HSCT for MS costs approximately $100,000 to $300,000 when done outside of a clinical trial. Some insurance plans have begun covering HSCT for MS, particularly after the MIST trial results, but coverage remains inconsistent. In countries with nationalized healthcare systems (Sweden, UK, parts of the EU), HSCT may be covered for qualifying patients.
Medical tourism for HSCT is common. Centers in Mexico (Clinica Ruiz), Russia (Pirogov National Medical Center), and Israel offer HSCT for MS at costs ranging from $30,000 to $80,000. Quality and safety standards vary significantly. Patients considering overseas treatment should thoroughly research the center’s experience, mortality data, and follow-up protocols.
MSC Therapy
MSC therapy for MS typically costs $5,000 to $20,000 per infusion in commercial settings, with most protocols involving multiple infusions. Clinical trial participation provides treatment at no cost but requires meeting specific eligibility criteria. MSC therapy is not FDA-approved for MS in the United States, and insurance does not cover it.
Where to Get Treatment
For HSCT, established programs in the United States include Northwestern University (Chicago), MD Anderson Cancer Center (Houston), and Cleveland Clinic. In Europe, centers in Sweden (Uppsala, Stockholm), the UK (Sheffield, London), and Italy (multiple centers) have extensive experience.
For MSC therapy, treatment is available through clinical trials (the safest and most scientifically rigorous option) and through private clinics in the US and internationally. When evaluating any clinic, ask about their specific protocol, cell source, quality control testing, published outcomes, and how they handle adverse events.
Making the Decision
Choosing stem cell therapy for MS is a significant decision that should be made collaboratively with your neurologist. Key considerations:
- HSCT is a real option for patients with aggressive RRMS who have failed or are failing standard DMTs. The evidence supports it. But it is a serious medical procedure with real risks, and patient selection matters enormously.
- MSC therapy is less proven but also less risky. It may be appropriate for patients who want a less aggressive approach or who have progressive disease where HSCT is less likely to help.
- Clinical trial participation is the ideal pathway when possible. You get access to cutting-edge treatment, rigorous monitoring, and contribute to the evidence base that will help future patients.
- Beware of clinics that promise cures. No stem cell therapy cures MS. HSCT can produce long-term remission in selected patients. MSC therapy may reduce disease activity. Any clinic guaranteeing outcomes is not being honest.
