Omalizumab

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.

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Mechanism of action

Omalizumab inhibits the binding of IgE to the high-affinity IgE receptor FcεRI (and presumably to FcεRII as well) on the surface of mast cells and basophils. Reduction in surface bound IgE on FcεRI-bearing cells limits the degree of release of mediators of the allergic response. Treatment with Xolair also reduces the number of FcεRI receptors on basophils in atopic patients.

Usage

Due to the lack of sufficient information on the long-term effectiveness and side effects of the drug, omalizumab treatment is not yet very common, and can be expensive. Another barrier to prevalent use is the injectable dosage form, which requires the patient to visit a physician's office or clinic every 2 to 4 weeks during treatment. Additionally, as IgE could be a natural defense against parasitic diseases, treatment is usually not recommended when living in environments where the presence of parasites is common.

Recent research suggests that IgE might play an important role in the immune system's recognition of cancer cells,^[1] so indiscriminate blocking of IgE / receptor interaction might have unforeseen problems. Clinical studies have shown that patients who underwent Xolair treatment had an increased (0.5%) chance of contracting malignancies (cancers) of various types, compared with patients who received the placebo drug (0.2%). This is considered a statistically significant increase. Concerns have also been raised about possible induction of Churg-Strauss syndrome, nasal polyps, and adrenal insufficiency.^[2]

Delivery

The drug is administered subcutaneously in 1 to 3 injections every 2 or 4 weeks.

Notes

• ^  Karagiannis SN, Wang Q, East N, Burke F, Riffard S, Bracher MG, Thompson RG, Durham SR, Schwartz LB, Balkwill FR, Gould HJ. Activity of human monocytes in IgE antibody-dependent surveillance and killing of ovarian tumor cells. Eur J Immunol 2003;33:1030-40. PMID 12672069.
• ^  Winchester D, Jacob A, Murphy T, Tonnel A, Tillie-Leblond I. Omalizumab for Asthma N Engl J Med 2006 355: 1281-1282.