The study objective is to compare the efficacy and the safety of masitinib at 6 mg/kg/day versus placebo in the treatment of patients with Severe Persistent Asthma treated with oral corticosteroids.

Masitinib is a selective tyrosine kinase inhibitor. It is known that activation of inflammatory cells, such as mast cells, and fibrous tissue remodeling are associated with c-Kit, Lyn and PDGFR kinase signaling pathways; all key targets of masitinib. The objective of this study is to compare the efficacy and safety of masitinib at 6 mg/kg/day versus matched placebo in severe persistent asthma patients that is uncontrolled with oral corticosteroids. The primary outcome measure will be severe asthma exacerbation rate over duration of the treatment.

Main inclusion criteria:

1. Patient with severe asthma and already treated with oral corticosteroids at a minimal daily dose of 7.5 mg prednisone or equivalent for at least 3 months prior to screening visit
2. Patient treated with oral corticosteroids during at least one period of 21 days, from 1 year prior to screening to 3 months before screening
3. Patient with no significant change in the regular asthma medication, no severe asthma exacerbation for at least 4 weeks prior to screening visit
4. Non-smoker patient for at least 1 year and with a prior tobacco consumption < 10 packs/year

Main exclusion criteria:

1. Patient with active lung disease other than asthma (e.g. chronic bronchitis)
2. Female patient who is pregnant or lactating
3. Asthmatic patient still exposed to allergens or to triggering factors influencing asthma control
4. Patient with history of acute infectious sinusitis or respiratory tract infection within 4 weeks prior to screening visit