Masitinib for multiple sclerosis

Written by Margarida Maia, PhD | Last updated Jan. 14, 2026
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What is masitinib for MS?

Masitinib is an investigational oral therapy being developed by AB Science for the treatment of progressive forms of multiple sclerosis (MS), including primary progressive MS (PPMS) and nonactive secondary progressive MS (SPMS).

Taken daily as oral tablets, masitinib has been found in a clinical trial to slow disease progression in these patient groups.

In MS, the immune system mistakenly attacks myelin — the protective coating around nerve fibers — causing ongoing inflammatory damage that leads to neurodegeneration.

Chronic neuroinflammation and neurodegeneration in progressive MS is thought to be driven in part by immune cells called mast cells and microglia. Activated mast cells release inflammatory molecules and weaken the protective barrier around the brain, while microglia are brain-resident cells that become pro-inflammatory when abnormally activated.

Masitinib, previously known as AB1010, works to block the activity of enzymes called tyrosine kinases that are involved in the activation and growth of these cells. In doing so, masitinib reduces the number of these immune cells in the brain, which is expected to reduce inflammation and slow the progression of MS.

AB Science is also testing masitinib for other neurodegenerative diseases, blood disorders, and mast cell-mediated conditions.

Therapy snapshot

Treatment name: Masitinib
Administration: Oral tablets
Clinical testing: Completed two trials for PPMS and nonactive SPMS; a Phase 3 trial is ongoing

How will masitinib be administered?

Masitinib is available in the form of film-coated oral tablets, which are taken twice daily. An ongoing Phase 3 clinical trial is testing it at a daily dose of 4.5 mg/kg, but it is too soon to know for sure which dose and regimen will be used if the drug is ultimately approved.

An infographic depicts the testing population, administration, and trial status of the experimental treatment masitinib.

Masitinib in MS clinical trials

Masitinib has been tested in two completed clinical trials involving a total of 646 adults with PPMS or nonactive SPMS.

  • A proof-of-concept Phase 2a clinical trial, called AB04011 (NCT01450488), enrolled 35 adults who were randomly assigned to receive masitinib — at a dose of 3 or 6 mg/kg per day — or a placebo for at least one year. While the results failed to reach statistical significance, the masitinib group showed a 103% increase in the MS Functional Composite (MSFC) scale — a composite measure of walking ability, dexterity, and cognitive function — while those on a placebo showed a 60% reduction. Also, a greater proportion of masitinib-treated patients were considered MSFC responders than those receiving a placebo (32% vs. 0%).
  • A larger Phase 2b/3 clinical trial, called AB07002 (NCT01433497), then enrolled 611 adults who were randomly assigned to masitinib — at a dose of 4.5 or 6 mg/kg per day — or a placebo, given twice daily for about two years. The trial met its main goal, with masitinib’s low dose outperforming a placebo at slowing disability progression, as measured by score changes on the Expanded Disability Status Scale (EDSS). Patients on this dose had a 42% lower risk of first disability progression and a 37% lower risk of three-month confirmed disability progression. Also, none reached a level of disability severe enough to require a wheelchair, while 4% of those given a placebo did.

Building on results from these two studies, AB Science launched a Phase 3 clinical trial, called MAXIMS (NCT05441488), which is currently testing twice-daily masitinib against a placebo in around 800 adults with PPMS or nonactive SPMS.

Participants on masitinib are receiving a 4.5 mg/kg dose following a four-week titration period on a lower dose of 3 mg/kg. The main goal is to determine whether masitinib can delay the time to three-month confirmed disability progression over about two years. The trial is expected to finish in 2028.

Masitinib side effects

Masitinib is still being tested in clinical trials for MS, so its safety profile is not fully established. So far, the most common side effects reported during clinical trials included:

  • diarrhea
  • rash
  • nausea or vomiting
  • swelling in the legs, arms, feet, and hands
  • itching
  • changes in blood tests, including low blood cell counts, decreased phosphorus, elevated sodium, and low hemoglobin, a red blood cell protein

Multiple Sclerosis News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.


FAQs about masitinib in MS

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How does masitinib help with multiple sclerosis?

Masitinib is an experimental oral therapy being tested as a potential treatment for progressive forms of multiple sclerosis (MS), including primary progressive MS and nonactive secondary progressive MS. It is a tyrosine kinase inhibitor designed to suppress immune cells that drive neurodegeneration in these MS types. In early clinical trials, the therapy helped slow the progression of disability in these patients.

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When will the FDA approve masitinib?

Masitinib has shown potential for slowing disease progression in progressive forms of multiple sclerosis (MS) in a Phase 2b/3 clinical trial. A larger Phase 3 trial is now underway to confirm these benefits. If the results are positive, masitinib could move closer to regulatory approval by the U.S. Food and Drug Administration, though this may still take several years.

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Can I take masitinib while pregnant?

Animal data suggest that masitinib may harm a developing fetus. However, clinical trials have not included pregnant or breastfeeding women, so it is not known if masitinib can be safely taken during pregnancy.

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How long should I wait to see the results of masitinib?

In a Phase 2b/3 clinical trial, masitinib helped slow disease progression in adults with progressive forms of multiple sclerosis (MS) over a period of nearly two years. More data are needed to establish when patients may first start to notice clinical benefits from masitinib.

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Does masitinib cause hair loss or weight gain?

Hair loss and weight gain have not been reported as side effects of masitinib in multiple sclerosis clinical trials. Patients are advised to consult their healthcare team if they experience any unexpected side effects from their medications.

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