A recombinant DNA-derived humanized IgG1k monoclonal antibody that selectively binds to human immunoglobulin E (IgE). Xolair is produced by a Chinese hamster ovary cell suspension culture in a nutrient medium containing the antibiotic gentamicin.
Also, it is not yet known what the potential long term effects of Xolair use may have on people who are prone to getting cancer (such as the elderly).
While it would appear that Xolair has potentially severe side effects, it must be remembered that anaphylaxis and cancer formation occurred only in a very small number of patients.
A large-scale prospective study of omalizumab is ongoing (The Epidemiologic study of Xolair (omalizumab): evaluating Clinical Effectiveness and Long-term Safety in patients with moderate-to-severe asthma (EXCELS study)) .
Binding constants (Kd) of FcεRIα and Xolair, and half maximal effective concentrations (EC50) of wt IgE-Fc3-4, mAb15.1, D17.4 and E2_79 were obtained by fitting the experimental data to a standard Michaelis-Menten model.
Protein therapies such as anti-IgE monoclonal antibody omalizumab (Xolair) for treating allergic airway constriction  and TNFα inhibitors in the field of rheumatoic arthritis and chronic inflammatory conditions  have shown their high effectiveness, but they can induce side-effects and are expensive therapies.