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Background Peanut allergy is a major public health problem that affects 1% of the population and has no effective therapy. Objective To examine the safety and efficacy of oraldesensitization in peanut allergic children in combination with a brief course of anti-IgE monoclonal antibody (omalizumab, Xolair). Methods We performed oral peanut desensitization in peanut allergic children at high risk for developing significant peanut-induced allergic reactions. Omalizumab was administered prior to and during oral peanut desensitization. Results We enrolled 13 children (median age, 10 years), with a median peanut-specific IgE of 229 kUA/L and a median total serum IgE of 621 kU/L, who failed an initial double-blind placebo controlled food challenge at doses 100 mg peanut flour. After pre-treatment with omalizumab, all subjects tolerated the initial 11 desensitization doses given on the first day, including the maximum dose of 500 mg peanut flour (cumulative dose, 992 mg, equivalent to >2 peanuts), requiring minimal or no rescue therapy. 12 subjects then reached the maximum maintenance dose of 4,000 mg peanut flour/day in a median time of 8 weeks, at which point omalizumab was discontinued. All 12 subjects continued on 4,000 mg peanut flour/day and subsequently tolerated a challenge with 8,000 mg peanut flour (equivalent to about 20 peanuts), or 160 to 400 times the dose tolerated before desensitization. During the study, 6 of the 13 subjects experienced mild or no allergic reactions; 6 subjects had Grade 2, and 2 subjects Grade 3 reactions, all of which responded rapidly to treatment. Conclusions Among children with high-risk peanut allergy, treatment with omalizumab may facilitate rapid oral desensitization, and qualitativelyimprove the desensitization process.

Background Peanut oral immunotherapy (OIT) is a promising approach to peanut allergy but reactions are frequent and some patients cannot be desensitized. The anti-IgE medication omalizumab (Xolair) may allow more rapid peanut updosing and decrease reactions. Objective To evaluate if omalizumab facilitated rapid peanut desensitization in highly allergic patients. Methods Thirty-seven subjects were randomized to omalizumab (n=29) or placebo (n=8). After 12 weeks of treatment subjects underwent a rapid one-day desensitization of up to 250 mg of peanut protein, followed by weekly increases up to 2000 mg. Omalizumab was then discontinued and subjects continued on 2000 mg of peanut protein. They underwent an open challenge to 4000 mg peanut protein twelve weeks after stopping study drug. If tolerated, subjects continued on 4000 mg of peanut protein daily. Results The median peanut dose tolerated on the initial desensitization day was 250 mg for omalizumab versus 22.5 mg for placebo treated subject. Subsequently 23 of 29 (79%) subjects randomized to omalizumab tolerated 2000 mg peanut protein 6 weeks after stopping omalizumab versus 1 of 8 (12%) receiving placebo (p<0.01). Twenty-three subjects on omalizumab versus 1 on placebo passed the 4000 mg food challenge. Overall reaction rates were not significantly lower in omalizumab versus placebo treated subjects (OR=0.57 p=0.15), although omalizumab treated subjects were exposed to much higher doses of peanut. Conclusion Omalizumab allows subjects with peanut allergy to be rapidly desensitized over as little as 8 weeks of peanut OIT. In the majority of subjects, this desensitization is sustained after omalizumab is discontinued. Additional studies will help clarify which patients would benefit most from this approach.

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