Efficacy and Safety of Masitinib in Corticosteroid-Dependent Severe Asthma: A Randomized Placebo-Controlled Trial

Background: Masitinib is an oral tyrosine kinase inhibitor that selectively targets mast cell activity and platelet-derived growth factor receptor (PDGFR) signaling, both of which are implicated in various mechanisms of asthma pathogenesis. Objective: Assessment of masitinib as an add-on to standard maintenance therapy as compared with placebo in the treatment of oral corticosteroid-dependent severe asthma. Methods: We conducted a randomized (2:1), placebo-controlled study of masitinib (6 mg/kg/d) in adults with severe asthma uncontrolled by high dose inhaled corticosteroids and long-acting beta-adrenoreceptor agonists plus oral corticosteroids (OCS) (=7.5 mg/d). No minimum baseline blood eosinophil count was specified. Following a protocol amendment, the primary endpoint was reduction of annualized severe asthma exacerbation rate adjusted for the overall time on treatment (SAER). Subgroup analysis according to yearly cumulative OCS intake was also performed, a higher OCS dose indicating more severe asthma that is harder to control. Results: Following an average exposure of approximately 13 months, masitinib (n = 240) reduced the SAER by 35% relative to placebo (n = 115) (rate ratio (RR) 0.65 (95% CI [0.47-0.90]; P = 0.010)). For patients with eosinophil >= 150 cell/mu L, masitinib (n = 181) reduced SAER by 38% relative to placebo (n = 87); RR 0.62 (95% CI [0.42-0.91]; P = 0.016). Benefit of masitinib was shown to increase in the most severely affected patients (OCS intake of >1000 mg/year), with a significant (P < 0.01) reduction in SAER of 50%-70%. Safety was consistent with the known masitinib profile. Conclusion: Orally administered masitinib reduces the risk of asthma exacerbations in severe asthma patients, with an acceptable safety profile. Masitinib may potentially provide a new treatment option for oral corticosteroid-dependent severe asthma.