Omalizumab in Chronic Spontaneous Urticaria: A Real-World Study on Effectiveness, Safety and Predictors of Treatment Outcome.

Background: Although omalizumab has shown success in treating chronic spontaneous urticaria (CSU) patients unresponsive to antihistamines, the exact mechanism of action and predictive markers of response remain unclear. Purpose: The aim of this study was to examine the correlation between baseline levels of biomarkers and clinical parameters with omalizumab response and response rate in patients with CSU. Methods: This retrospective study included 82 adult CSU patients who received omalizumab 300mg every 4 weeks for 16 weeks between January 2022 and December 2023. Treatment response was assessed using UAS7 and DLQI scores at baseline and weeks 4, 8, 12, and 16. Responders were defined as patients achieving UAS7 < 7, with early and late responders categorized based on response within or after 4 weeks, respectively. Baseline clinical features and laboratory biomarkers were compared between responders and non-responders. Results: The overall response rate was 71.95% (59/82), with 23 early responders and 36 late responders. Responders had significantly lower baseline UAS7 (median: 28 vs 35, P < 0.01), DLQI (median: 8 vs 15, P < 0.001), and IL-17 levels (median: 0.53 vs 1.26 pg/mL, P < 0.001) compared to non-responders. Baseline UAS7 > 31, DLQI > 9.5, and IL-17 > 0.775 pg/mL predicted non-response with sensitivities of 78.26%, 100%, and 78.26%, and specificities of 67.8%, 59.32%, and 72.88%, respectively. ASST positivity and comorbid allergic diseases were associated with early response (P < 0.05). Adverse events were reported in 6.09% of patients, including mild injection site reactions and transient urticaria exacerbation, not requiring treatment discontinuation. Conclusion: This study suggests that omalizumab is an effective and safe treatment option for antihistamine-refractory CSU. Baseline UAS7, DLQI, ASST status, serum total IgE levels, and IL-17 may serve as potential predictors of omalizumab response. Notably, ASST positivity and comorbid allergic diseases were associated with an early response to treatment. These findings highlight the importance of considering individual patient characteristics when predicting the likelihood and timing of response to omalizumab in CSU.