Phase III data demonstrates Masican (masitinib) superiority in severe mastocytosis- AB Science

AB Science has announced results from phase III study of Masican (masitinib), in the treatment of adult patient with severe systemic mastocytosis unresponsive to optimal symptomatic treatment. The study compared masitinib plus optimal symptomatic treatment versus placebo plus optimal symptomatic treatment in adult patients with severe systemic mastocytosis, with or without D816V mutation of c-Kit.

Study results showed that masitinib administered at 6 mg/kg/day was superior to the comparator, as measured by the cumulative 75% response rate until week 24 on the handicaps of pruritus or flushes or depression or fatigue (4H75% response). The 4H75% response was 18.7% for the masitinib treatment-arm versus 7.4% for the placebo treatment-arm in the mITT population (primary analysis). Sensitivity analysis according to the per protocol (PP) population, i.e. the sets of patients who participated in the study as intended, gave a 4H75% response rate of 20.1 % versus 7.4%, respectively.

In addition, the cumulative 75% response rate until week 24 on the handicaps of pruritus or flushes or depression (3H75% response) was 24.7% versus 9.8% for the masitinib and placebo treatment-arms, respectively, in the mITT population. In the per protocol population this response rate was 26.5 % versus 9.8%, respectively. When looking at other individual handicaps of flush, Hamilton, and FIS (Fatigue Impact Scale), a consistent superiority was observed for all handicaps, showing that masitinib can reduce each of these symptoms.

Comment: Mastocytosis is an orphan disease characterized by an abnormal proliferation or activation of mast cells either in the skin or in bone marrow or other organs. Mastocytosis comes in two main forms: indolent and aggressive. Indolent forms of mastocytosis can be either cutaneous or systemic. The prevalence of indolent systemic mastocytosis, including smoldering systemic mastocytosis, is estimated to be 1/26,000 in Europe. The symptoms and handicaps are severe in about one third of the patients; hence, an estimated target population for masitinib of approximately 1/78,000 of the general population.