Omalizumab

Omalizumab (Xolair) is a medication originally designed to reduce sensitivity to allergens and is used for treating chronic idiopathic urticaria and allergic asthma. It is a potential treatment for mast cell disorders.

Mechanism
It is a monoclonal antibody that binds to free immunoglobulin E (IgE) in the blood and interstitial fluid and to membrane-bound form of IgE (mIgE) on the surface of mIgE-expressing B cells. It inhibits the binding of IgE to FcεRI on mast cells and basophils by binding to an antigenic epitope on IgE that overlaps with the site to which FcεRI binds. In this sense, it is a potent mast cell stabilizer.

Research on mast cell disorders
In a study of 55 French patients with mast cell disorders treated with omalizumab, 43 patients achieved a "best response" and 76.7% of the responding patients achieved a persistent response (three months or longer.) Median time to first response was 2 months and median time to best response was 6 months. One severe adverse event occurred, with researchers suggesting this recommends initiating treatment in hospital, but otherwise found the safety profile acceptable.