Emma Hitt, PhD

March 12, 2003

March 12, 2003 (Denver) — The anti-IgE monoclonal antibody omalizumab appears to inhibit IgE-mediated nasal symptoms within a week, which suggests that it could be useful in quickly controlling symptoms of allergic rhinitis, a new study suggests.

Although omalizumab is known to improve symptoms of allergic respiratory disorders, its onset of action is unknown. Therefore, Henry Lin, MD, an allergist with Creighton University in Omaha, Nebraska, and colleagues examined the kinetics of inhibition in 24 patients with ragweed allergic rhinitis challenged with ragweed.

The researchers presented the findings here at the 60th annual meeting of the American Academy of Allergy, Asthma, and Immunology on Tuesday.

Patients were randomized to receive omalizumab or placebo in a 2:1 ratio and were challenged with serial concentrations of ragweed to determine the dose eliciting a 30% decrease in nasal volume as measured by acoustic rhinometry (PD30).

Either a placebo or approximately 0.016 mg/kg/IgE IU/mL omalizumab was administered at day 0 and day 28. Patients were rechallenged with the ragweed PD30 dose every two weeks for six weeks.

Mean IgE levels decreased from 258 ± 51 ng/mL to 11 ± 1 ng/mL ( P < .001) within 3 days in the omalizumab group, and the levels stayed low throughout the six-week study, the researchers report.

In patients receiving omalizumab, response to the baseline PD30 dose was decreased to 19.6% at 7 to 14 days ( P < .01); 19.0% at 21 to 28 days ( P < .01); and 13.6% at 35 to 42 days ( P < .001). In contrast, the patients receiving placebo did not show a significant response during the study.

"Omalizumab's inhibition of ragweed-induced nasal allergen challenge persisted throughout the six-week study period," Dr. Lin concluded during his presentation.

"We were pleased with the results," Dr. Lin told Medscape. "Omalizumab quickly improved symptoms of allergic rhinitis," although the study was not powered to measure symptoms, but rather the kinetics of the IgE response, he pointed out.

Currently, Dr. Lin's group is evaluating omalizumab in people undergoing immunotherapy. "It typically takes up to six months of injections to get these patients up to a level where they have reduced symptoms," Dr. Lin said. "But giving omalizumab alongside the immunotherapy may make it safer to administer the allergy shots over a couple of weeks," he said.

Session moderator Michael J. Schumacher, MD, professor of pediatrics at the University of Arizona in Tucson, noted that omalizumab clearly suppressed IgE levels and did so very rapidly.

According to Dr. Schumacher, the effectiveness of omalizumab, when given in intervals that range up to several weeks, suggest that it's going to be practical to use. "It won't need to be injected every couple of days — the effect might be quite long lasting," he said.

The study was funded by Genentech.

AAAAI 60th Annual Meeting: Abstract 1118. Presented March 11, 2003.

Reviewed by Gary D. Vogin, MD

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