Masitinib (also known as Kinavet® and Masivet®)

Experimental Medications: Other Therapeutic Strategies

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Masitinib is termed a protein kinase inhibitor. It selectively inhibits molecules (kinases) that play a major role in the activation of mast cells. Although mast cells are best known for their role in allergies, they are also involved in the immune response, in the recruitment of lymphocytes to the brain and also in inflammatory processes associated with MS. As noted earlier, lymphocytes are immune-system cells produced to fight infection and disease. Additionally, lymphocytes can initiate myelin damage.

Masitinib has a role in veterinary medicine (it is used to fight mast cell tumors in dogs) and is being studied for several human indications, including cancers and degenerative diseases. A small Phase II trial of masitinib in progressive forms of MS21 showed a trend toward benefit; however, the results were not statistically significant.22

In 2012, results from a Phase II study of 30 patients taking masitinib were released. These indicated what is termed “proof of concept,” showing that this agent may have potential in treating both PPMS and relapse-free SPMS. The study investigated the hypothesis that masitinib’s action of targeting and inhibiting mast cells may delay the onset of symptoms associated with progressive forms of MS.

The results showed that for the primary endpoint of Multiple Sclerosis Functional Composite (MSFC) score, which measures upper and lower limb function as well as cognition, 32 percent of patients treated with masitinib showed a response to treatment versus none of those receiving a placebo. Responses were seen in the third month and were sustained over the 18-month duration of the study.

A Phase IIb/III multicenter, randomized, double-blind, placebo-controlled trial23 is currently underway. The investigators planned to recruit 450 people with PPMS or SPMS without relapses. The primary endpoint will be an improvement in the MSFC scale at 96 weeks. In summer 2015, the trial sponsor announced that after one third of patients enrolled in the trial were treated for a total of 48 weeks (halfway through the trial), they were assessed for an array of disability endpoints. The observed changes were significant enough for the masitinib trial to be declared “non futile” by the Independent Data Safety Monitoring Committee. This decision indicates that the Phase III clinical trial has the potential to succeed and is thus justified to continue forward.

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