Amiselimod (formerly known as MT-1303) is an investigational therapy for people with relapsing-remitting muscular sclerosis (RRMS), inflammatory bowel disease (IBD), and other autoimmune diseases. The treatment was originally developed by Mitsubishi Tanabe Pharma (MT Pharma) and briefly licensed to Biogen for further development and testing in clinical trials. That license has since returned to MT Pharma.

How Amiselimod works

Amiselimod is a sphingosine 1-phosphate (S1P) receptor modulator. S1P receptors are a type of protein expressed on the surface of immune cells (lymphocytes). The binding of the S1P molecule to its receptor is required for the movement of lymphocytes out of the lymph nodes and into circulating blood. In MS patients, lymphocytes (such as T- and B-cells) can move into the brain and spinal cord and cause inflammation, which leads to nerve damage.

Amiselimod interferes with S1P signaling to prevent lymphocytes from exiting the lymph nodes — keeping them trapped inside the node. The result is a reduction in circulating T- and B-cells, leading to anti-inflammatory activity. The treatment’s intent is to reduce continuing nerve damage and slow MS progression by reducing inflammation.

Amiselimod in clinical trials

A Phase 2 study called MOMENTUM (NCT01742052) was carried out to assess the safety and efficacy of amiselimod at different doses (0.1, 0.2 and 0.4 mg), compared to a placebo, over a 24-week period in 415 patients with RRMS. The trial’s results, published in 2016, were promising. Amiselimod (at 0.2 and 0.4 mg) significantly reduced the total number of brain lesions and had a safety and efficacy profile that seemed to support further studies in RRMS patients.

The most common adverse effects associated with treatment were headaches and the common cold. Other and more serious side effects, such as infections and cardiac disorders, were similar between the amiselimod- and placebo-treated groups in the study.

Although the trial results, published in the Lancet Neurology and Nature Reviews Neurology, were promising, Biogen announced in October 2016 that it had discontinued the development of amiselimod without explanation. Following this, MT Pharma regained development rights for amiselimod and announced in early 2017 that it intends to continue developing the drug on its own or with a new partner.

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