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PEDIATRICS Vol. 113 No. 4 April 2004, pp. e308-e312

ELECTRONIC ARTICLE

Exhaled Nitric Oxide in Children With Asthma Receiving Xolair (Omalizumab), a Monoclonal Anti-Immunoglobulin E Antibody

Philip E. Silkoff, MD^*, Francisco A. Romero, MS, Niroo Gupta, MD, PhD, Robert G. Townley, MD and Henry Milgrom, MD^*

^* Departments of Medicine and Pediatrics, National Jewish Medical and Research Center and the University of Colorado Health Sciences Center, Denver, Colorado
Division of Allergy, Creighton University, Omaha, Nebraska
Novartis Pharmaceuticals Corporation, East Hanover, New Jersey

Objective. To evaluate the effect of a humanized monoclonal antibody to immunoglobulin E, omalizumab (Xolair, Novartis Pharmaceuticals, East Hanover, NJ; Genentech Inc, South San Francisco, CA), on airway inflammation in asthma, as indicated by the fractional concentration of exhaled nitric oxide (FE_NO), a noninvasive marker of airway inflammation. Xolair was approved recently by the US Food and Drug Administration for moderate-to-severe allergic asthma in adolescents and adults.

Study Design. As an addendum at 2 sites to a randomized, multicenter double-blind, placebo-controlled trial, FE_NO was assessed in children with allergic asthma over 1 year. There were 3 consecutive study periods: 1) stable dosing of inhaled beclomethasone dipropionate (BDP) when the dose was optimized (period of 16 weeks); 2) inhaled steroid-reduction phase (period of 12 weeks), during which BDP was tapered if subjects remained stable; and 3) open-label extension phase, during which subjects receiving placebo were switched to active omalizumab (period of 24 weeks). The primary outcome was area under the FE_NO versus time curve (AUC) for adjusted FE_NO, defined as the ratio of FE_NO at each time point compared with the value at baseline.

Results. Twenty-nine subjects participated and were randomized to omalizumab (n = 18) and placebo (n = 11) treatment groups in a 2:1 ratio dictated by the main study. There was a significant difference for age, resulting in a difference in absolute forced expiratory volume in 1 second but no difference in asthma severity based on the forced expiratory volume in 1 second percentage predicted. Baseline BDP dose was comparable between groups, as were baseline values of mean FE_NO (active: 38.6 ± 25.6 ppb; placebo: 52.7 ± 52.9 ppb). The degree of BDP dose reduction during the steroid-reduction and open-label phases was equivalent between the omalizumab and placebo-treated groups; subjects in the omalizumab- and placebo-treated groups had reduced their BDP dose by an average of 51% and 60%, respectively, at the end of the steroid-reduction phase and by 68% and 94%, respectively, by the end of the open-label period. In the active and placebo groups, 44% and 27% and 75% and 73% of subjects had stopped use of inhaled corticosteroids at the end of the steroid-reduction and open-label phases, respectively. There was no significant difference between the active and placebo groups during the steroid-stable phase for AUC of adjusted nitric oxide (1.31 ± 1.511 vs 1.45 ± 0.736). However, during the steroid-reduction phase, the variability of adjusted FE_NO in the placebo-treated group was greater than that of the omalizumab-treated group at most visits, with a significant difference between groups for AUC of adjusted nitric oxide (0.88 ± 0.69 vs 1.65 ± 1.06). FE_NO fell from 82.1 ± 55.6 ppm at the end of the steroid-reduction phase to 33.3 ± 21.6 ppb at the end of the open-label period in the placebo group who were placed on active omalizumab. This decrease occurred while the mean dose of BDP remained very low. Analysis of FE_NO over 52 weeks of omalizumab treatment in the active group demonstrated that there was a significant reduction from baseline to the end of the open-label period (41.9 ± 29.0 to 18.0 ± 21.8 ppb) despite a high degree of steroid reduction.

Conclusion. In this preliminary study based on FE_NO, a noninvasive marker of airway inflammation, treatment with omalizumab may inhibit airway inflammation during steroid reduction in children with allergic asthma. The degree of inhibition of FE_NO was similar to that seen for inhaled corticosteroids alone, suggesting an antiinflammatory action for this novel therapeutic agent in asthma. This is in keeping with recent evidence that omalizumab inhibits eosinophilic inflammation in induced sputum and endobronchial tissue.

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Key Words: asthma • exhaled • nitric oxide • omalizumab

Abbreviations: IgE, immunoglobulin E • FcRI, high-affinity IgE receptor • ICS, inhaled corticosteroid • NO, nitric oxide • NOS, NO synthase • FE_NO, fractional concentration of exhaled NO • BDP, beclomethasone dipropionate • FEV₁, forced expiratory volume in 1 second • SD, standard deviation • AUC, area under curve

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Received for publication Apr 9, 2003; Accepted Nov 20, 2003.

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