Masitinib: the first drug slowing progressive MS pathology
Multiple sclerosis (MS) is a long-life condition that affects the brain and spinal cord resulting in impaired vision, limb movement, sensation and balance. There are two main types in which MS pathology begins; relapsing-remitting and primary progressive. Relapsing-remitting has a higher incidence, affecting 80% of MS patients. Whereas primary progressive MS occurs in 10–15% of MS cases.1,2 However, patients with relapsing-remitting MS can develop progressive symptoms over the course of their disease.3
Currently, there is no cure for MS, and treatment mainly focuses on symptom relief. For relapsing-remitting MS, there are disease-modifying drugs that can help reduce the frequency of episodes, yet for progressive MS, there is no treatment to slow disease progression.
However, a recent Phase III clinical trial by AB Science (NCT01433497) has shown promising results with masitinib – a kinase inhibitor that targets receptors KIT, LYN and CSF1R on mast cells, macrophages and microglia. Microglia and mast cells are active in MS pathogenesis through the release of mediators that initiate and sustain inflammation.4
In the Phase III trial, 300 patients with primary progressive and non-active secondary progressive MS were randomized and evaluated in 2 independent parallel groups; 4.5 mg/kg/d vs matched placebo and a titrated dose of 6.0 mg/kg/d vs placebo. Patients were treated over 96 weeks and evaluated at 12-weekly intervals using the Expanded Disability Status Scale (EDSS). The primary endpoint of the study was the overall change in EDSS from baseline using repeated measures.3
Results from the trial showed that masitinib at a dose of 4.5 mg/kg/day had a significant benefit over the placebo with a change in EDSS of 0.001 vs 0.098, respectively (p=0.0256), indicating slowed disease progression. The sensitivity analysis based on ordinal EDSS change showed a significant 39% relative probability of either reduction in EDSS progression or an increase in EDSS improvement with masitinib treatment (p=0.0446). The efficacy for the higher dose group at 6.0mg/kg/day was inconclusive.3
These results indicate that targeting the innate immune system could provide a new treatment option for patients with MS.
Written by Emily Toyn
Edited by Marta Palhas
1. Multiple sclerosis. nhs.uk. Available from: https://www.nhs.uk/conditions/multiple-sclerosis/ (Last accessed 28/09/20).
2. Miller, D. H. & Leary, S. M. Primary-progressive multiple sclerosis. Lancet Neurol.2007; 6, 903–912.
3. Science, A. B. AB Science Presents Phase 2B/3 Study Results in Progressive Multiple Sclerosis at the World’s Largest Multiple Sclerosis Research Conference. GlobeNewswire News Room. Available from: http://www.globenewswire.com/news-release/2020/09/14/2092661/0/en/AB-Science-Presents-Phase-2B-3-Study-Results-in-Progressive-Multiple-Sclerosis-at-the-World-s-Largest-Multiple-Sclerosis-Research-Conference.html (Last accessed 28/09/20).
4. Vermersch, P. et al. Masitinib treatment in patients with progressive multiple sclerosis: a randomized pilot study. BMC Neurol.2012; 12, 36.