Omalizumab (marketed under the name Xolair®) is a monoclonal antibody made by Genentech / Novartis and used mainly in allergy-related asthma therapy, with the purpose of reducing allergic hypersensitivity. Xolair (Omalizumab) is a recombinant DNA-derived humanized IgG1k monoclonal antibody that selectively binds to human immunoglobulin E (IgE). IgE is commonly involved with allergies when present in high amounts in the body.
Recent research suggests that IgE might play an important role in the immune system's recognition of cancer cells, so indiscriminate blocking of IgE / receptor interaction might have unforeseen problems.
More on [ Omalizumab ]

FDA Approves Omalizumab (Xolair), a Recombinant Anti-IgE Antibody, to Treat Allergic Rhinitis and Allergic Asthma - June 2003 article on the drug's US approval. Includes information about results of clinical trials.
The Johns Hopkins Gazette: May 10, 1999 - Article about clinical testing of the experimental anti-allergy agent Anti-IgE, in a version called rhuMAb-E25.
Xolair - FamilyDoctor.org - Information for patients in English or Spanish.
Xolair: New Hope for Asthma and Allergy Sufferers - Article about this medication under development by Genentech, from Vanderbilt University.