Omalizumab chronic spontaneous urticaria: Efficacy, safety, predictors of treatment outcome, and time to response

Background: Omalizumab is a recombinant anti-immunoglobulin E (IgE) antibody used in the treatment of patients with chronic spontaneous urticaria (CSU). Objective: This multicentric study assessed the safety and efficacy of omalizumab in patients (n=322) with CSU refractory to second-generation antihistamines, also investigating predictors of poor treatment outcome and time lag to response to anti-IgE therapy by serum auto-reactivity. Methods: This retrospective observational study comprised a 4-week pretreatment period, a 24-week treatment period with omalizumab (300 mg/month), and a 16-week follow-up period. Primary efficacy endpoints were mean and median change in 7-day urticaria activity score (UAS7), weekly itch severity score (ISS), and hive score from baseline to 4-, 12-, and 24-week values. Secondary endpoints included the proportion of patients (defined “responders”) with well-controlled urticaria (UAS7 ≤ 6) and complete treatment response (UAS7=0). Safety in terms of side effects was also assessed. Results: Omalizumab significantly and consistently reduced the mean UAS7, ISS, and hive score from baseline to weeks 4, 12, and 24, with a clear decreasing trend over time. At the end of the treatment period (week 24), 84.2% of patients had a UAS7 score of 6 or less and 66.7% had a UAS7 of 0. Higher pretreatment IgE levels were less likely to be associated with poor treatment response (ie, UAS7 > 6). Patients with a positive autologus serum skin test (ASST) were significantly more likely to be “slow responders” to omalizumab treatment (ie, response beyond 8 days since omalizumab administration) than ASST-negative patients (P <.001). No treatment-related adverse events were recorded. Conclusion: Monitoring baseline characteristics of patients before introduction of omalizumab therapy may help to predict treatment outcome in CSU patients.