Omalizumab pretreatment decreases acute reactions after rush immunotherapy for ragweed-induced seasonal allergic rhinitis

Background: Rush immunotherapy (RIT) presents an attractive alternative to standard immunotherapy. However, RIT carries a much greater risk of acute allergic reactions, including anaphylaxis. Objectives: We hypothesized that omalizumab, a humanized monoclonal anti-IgE antibody, would be effective in enhancing both safety and efficacy of RIT. Methods: Adult patients with ragweed allergic rhinitis were enrolled in a 3-center, 4-arm, double-blind, parallel-group, placebo-controlled trial. Patients received either 9 weeks of omalizumab (0.016 mg/kg/IgE [IU/mL]/mo) or placebo, followed by 1-day rush (maximal dose 1.2-4.0 μg Amb a 1) or placebo immunotherapy, then 12 weeks of omalizumab or placebo plus immunotherapy. Results: Of the 159 patients enrolled, 123 completed all treatments. Ragweed-specific IgG levels increased >11-fold in immunotherapy patients, and free IgE levels declined >10-fold in omalizumab patients. Patients receiving omalizumab plus immunotherapy had fewer adverse events than those receiving immunotherapy alone. Post hoc analysis of groups receiving immunotherapy demonstrated that addition of omalizumab resulted in a 5-fold decrease in risk of anaphylaxis caused by RIT (odds ratio, 0.17; P = .026). On an intent-to-treat basis, patients receiving both omalizumab and immunotherapy showed a significant improvement in severity scores during the ragweed season compared with those receiving immunotherapy alone (0.69 vs 0.86; P = .044). Conclusion: Omalizumab pretreatment enhances the safety of RIT for ragweed allergic rhinitis. Furthermore, combined therapy with omalizumab and allergen immunotherapy may be an effective strategy to permit more rapid and higher doses of allergen immunotherapy to be given more safely and with greater efficacy to patients with allergic diseases.