A randomized, placebo-controlled, dose-ranging study of single-dose omalizumab in patients with H₁-antihistamine-refractory chronic idiopathic urticaria

Background: Proof-of-concept studies with omalizumab in patients with chronic idiopathic urticaria (CIU) have shown significant decreases in mean urticaria activity scores (UASs). Objective: We sought to evaluate the efficacy and safety of omalizumab in patients with CIU who remain symptomatic despite concomitant H₁-antihistamine therapy. Methods: This phase II, prospective, double-blind, placebo-controlled, dose-ranging study investigated omalizumab in patients aged 12 to 75 years in the United States and 18 to 75 years in Germany with a UAS over 7 days (UAS7) of 12 or greater despite antihistamine therapy. Patients were randomized 1:1:1:1 to receive a single subcutaneous dose of 75, 300, or 600 mg of omalizumab or placebo added to a stable dose of H₁-antihistamine. The primary efficacy outcome was change from baseline to week 4 in UAS7. Patients were followed for an additional 12 weeks to monitor safety. Results: Ninety patients from the United States or Germany were enrolled. Both the 300-mg omalizumab group (-19.9 vs -6.9, P <.001) and the 600-mg omalizumab group (-14.6 vs -6.9, P =.047) showed greater improvement versus the placebo group in UAS7. No meaningful difference was observed for the 75-mg omalizumab group. Similar results were seen for key secondary end points of weekly hive and itch scores. Onset of effect occurred after 1 to 2 weeks. Omalizumab was well tolerated, and the incidence of adverse events was similar across treatment groups. Conclusion: This study demonstrated that a fixed dose of 300 or 600 mg of omalizumab provides rapid and effective treatment of CIU in patients who are symptomatic despite treatment with H ₁-antihistamines.