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Am Fam Physician. 2005;71(2):341-342


Omalizumab is a recombinant humanized monoclonal antibody (rhuMAb-E25) labeled for treatment of moderate to severe persistent asthma in persons 12 years or older.1 Omalizumab is the first biotechnology drug for treatment of allergy-induced asthma. It works by inhibiting binding of IgE to its receptor, located on mast cells and basophils. This action prevents release of mediators of allergic response (e.g., histamine) that cause bronchospasm.

NameStarting dosageDose formApproximate cost*
Omalizumab (Xolair)150 to 375 mg subcutaneously, every 2 or 4 weeks (based on patient’s weight and serum IgE level)5-mL vial containing 150 mg omalizumab for injection150 mg: $541 (for 2 weeks), $1,082 (for 4 weeks)†
375 mg: $1,353 (for 2 weeks), $2,706 (for 4 weeks)†


Studies with omalizumab identified two major safety issues: emergence of malignancies and anaphylaxis. Malignancies are not limited to any one type and, in studies, have occurred in 0.5 percent of patients treated with omalizumab for less than one year as compared with 0.2 percent in controls, though the difference was not statistically significant.1 Anaphylactic reactions, including urticaria or tongue and/or throat edema, may occur within two hours after initial or subsequent injections and require that the injection be administered in a physician’s office so that the patient may be monitored after administration.1 Severe anaphylactic reactions require omalizumab to be discontinued. To date, no drug interactions with omalizumab have been identified, although evaluation is limited.1 Omalizumab is pregnancy category B.


Use of omalizumab is associated with several side effects, including injection site reactions (45 percent), viral (23 percent) and upper respiratory tract (20 percent) infections, headache (15 percent), sinusitis (16 percent), pharyngitis (11 percent),1 and urticaria.2 Injection-site reactions tend to occur within one hour after injection, last about eight days, and decease in frequency with repeat injections. Urticaria responds to antihistamine treatment.2 Less than 0.1 percent of omalizumab-treated patients in studies have developed antibodies to omalizumab.1 In one study, a total of 2.8 percent of subjects on omalizumab and 4.8 percent of subjects on placebo withdrew from the study due to adverse events.2


Omalizumab has been studied in children and adults with moderate to severe allergic asthma. Most of the studies lasted less than one year. There is one meta-analysis of eight trials involving a total of 2,037 subjects with mild to severe allergic asthma.3 Patients treated with omalizumab were able to significantly reduce their daily corticosteroid dosage by at least 50 percent (four trials; odds ratio 2.50, 95 percent confidence interval (CI), 2.02 to 3.10) or stop its use altogether (four trials; odds ratio 2.50, 95 percent CI 2.00 to 3.13).3 Patients receiving omalizumab also were less likely to experience severe asthma exacerbation, either during the phase when steroid dosing remained constant or when a dose reduction in steroids was attempted. In a recently published study, omalizumab meaningfully improved disease control as well as asthma-related quality of life (QOL),4 with a significantly greater proportion of patients who took omalizumab achieving a clinically relevant improvement in QOL score of at least 1.5 points from baseline as compared with placebo, from a baseline score of 4.0 out of a possible 7 points. The authors in the study defined a clinically meaningful improvement as 0.5 points or more from baseline, and 1.5 or more was defined as a large improvement.

In a pooled analysis of three randomized, double-blind, placebo-controlled studies including 1,071 subjects older than 12 years and 334 subjects ages six to 12 years, treatment resulted in fewer unscheduled asthma-related outpatient visits in the treated group as a whole. One unscheduled outpatient visit was prevented for every seven patients receiving omalizumab rather than placebo over the course of a year (21.3 visits per 100 patients per year versus 35.5 visits per 100 patients per year; number needed to treat to prevent one visit = 7). Emergency room visits also occurred significantly less often in the omalizumab-treated group, with one visit prevented for every 50 patients teated for one year. Hospitalizations were decreased as well, with one fewer asthma-related hospitalization occurring for every 50 patients treated for one year.5 Patients receiving omalizumab were able to reduce their use of inhaled corticosteroid therapy compared with patients receiving placebo. There are no published trials that studied omalizumab in combination with immunotherapy for treatment of allergic asthma.


A one-month supply of omalizumab will cost patients between $541 and $2,706, depending on the dosage. This price is much higher than the cost of conventional treatments for asthma.


To qualify for treatment with omalizumab, patients also must have a positive skin test (IgE level between 30 IU per mL and 700 IU per mL) or in vitro reactivity to a perennial inhaled allergen and their asthma should be uncontrolled with inhaled oral corticosteroids.1 Inhaled corticosteroids should not be abruptly stopped at initiation of omalizumab treatment. The usual dosage of omalizumab is 150 to 375 mg subcutaneously every 2 or 4 weeks, based on patient weight and serum total IgE level (measured before treatment is started). The drug should be administered in the office to observe the patient for anaphylaxis. Effectiveness is monitored via symptom response.

Bottom line

Omalizumab is an immunomodulatory therapy for the control of symptoms in patients with moderate to severe allergic asthma uncontrolled with conventional therapy. Given its high cost, the requirement that it be administered in a physician’s office, and side effects, it is appropriate for use in only a small percentage of patients with asthma.

STEPS new drug reviews cover Safety, Tolerability, Effectiveness, Price, and Simplicity. Each independent review is provided by authors who have no financial association with the drug manufacturer.

This series is coordinated by Allen F. Shaughnessy, PharmD, assistant medical editor.

A collection of STEPS published in AFP is available at

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