Amiselimod for Multiple Sclerosis

Last updated June 28, 2022, by Marisa Wexler, MS

Fact-checked by Inês Martins, PhD

What is amiselimod for MS?

Amiselimod, previously called MT-1303, is an oral medication that’s been tested in clinical trials for treating multiple sclerosis (MS) and other autoimmune disorders.

It was developed by Mitsubishi Tanabe Pharma (MT Pharma), which licensed it in 2019 to Salix Pharmaceuticals, a subsidiary of Bausch Health, for certain autoimmune diseases. MT Pharma retained the rights to develop amiselimod for multiple sclerosis, but discontinued the Phase 2 development for that indication in 2021.

How does amiselimod work in MS?

Amiselimod works by modulating the activity of the sphingosine 1-phosphate (S1P) receptor, a protein expressed by certain immune cells. The S1P receptor normally is needed for these cells to exit out of lymph nodes, immune organs where they are matured and stored.

By modulating this receptor, amiselimod is designed to keep immune cells “trapped” inside lymph nodes. This may prevent them from migrating to the brain and spinal cord and causing the damaging inflammation that drives MS.

How will amiselimod be administered in MS?

Amiselimod has been tested in multiple sclerosis as a hard capsule, taken by mouth once per day. Clinical trials have evaluated doses from 0.1 to 0.4 mg per day.

Amiselimod in MS clinical trials

MT Pharma conducted three Phase 1 trials (NCT02193217, NCT02293967, NCT02310048) that tested amiselimod’s safety and pharmacological properties in healthy volunteers.


The company also ran a Phase 2 study, called MOMENTUM (NCT01742052), which enrolled 415 adults (ages 18 to 60) with relapsing-remitting multiple sclerosis (RRMS). Participants were assigned to take one of three amiselimod doses (0.1, 0.2, or 0.4 mg) or a placebo, daily for 24 weeks, or about half a year.

The study’s main goal was to assess the effect of treatment on the total number of actively inflamed disease lesions from weeks eight to 24. Results showed no difference between a placebo and the 0.1 mg/day dosage; however, those given the two higher doses of amiselimod had significantly fewer lesions with active inflammation than those given a placebo. In fact, patients taking the 0.2 mg dose were 4.5 times more likely than those on a placebo to be free from these lesions at week 24, and those on the 0.4 mg dose were 10 times more likely.

The number of new and enlarging lesions from week four to 24 also was significantly lower among those on the highest doses, by over 50%, compared with people taking a placebo. Also, the 0.4 mg dose reduced the number of relapses per year compared with any other group. None of the doses impacted disability progression, or changes in measures such as dexterity, walking function, and cognition.

The therapy was generally well tolerated, with rates of treatment-emergent side effects being similar across the groups.

After the initial MOMENTUM study, 367 participants entered an extension study (NCT01890655), where all were given amiselimod at one of the three doses for an additional 72 weeks.

Results indicated the lesion-reducing effect seen in the original study was sustained with long-term treatment, with more than 80% of patients on the highest doses being free from lesions with active inflammation after 48 weeks. Relapse rates over the 96 weeks also remained 55% lower among patients always on amiselimod, compared with those who first received a placebo.

Common side effects of amiselimod

The most common side effects associated with amiselimod in the MOMENTUM trial and its extension were:

  • headache
  • the common cold
  • low immune cell counts


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