The prevalence of patients suffering from chronic spontaneous urticaria, in whom omalizumab cannot be stopped even after six years.

Background: Omalizumab (OMA) was the first FDA-approved biological drug for severe chronic spontaneous urticaria (CSU), and until today is the only beneficial and truly safe one. The objectives were: To assess the prevalence of CSU patients in whom OMA cannot be stopped over time. We also asked if biomarkers (e.g., anti-TPO antibodies and total IgE) could assist in anticipating this issue. Methods: We used our prospective registry of 93 patients, which included CSU disease duration, the onset of OMA treatment, Urticaria Activity Score (UAS7) during follow-up, co-morbidities, serum IgE levels and the presence of anti-TPO antibodies. Finally, we assessed the response to OMA during a period of six years. Results: Out of the 93 treated CSU patients, OMA was stopped in ten patients after six months being defined as failures. In another ten patients, OMA was discontinued after 2-4 years of therapy, achieving a remission. Seventy-three patients are still treated between 2 and 6 years, having different degrees of response. Of these, in thirty-eight (52%) patients, we could not stop OMA even after six years due to CSU relapses. The prevalence of lower serum IgE levels and anti-TPO antibody positivity was significantly higher in CSU patients in whom OMA could not be stopped. Conclusion: This is the first study where OMA-treated CSU patients were followed up to six years. In half of them, long-term therapy of six years is still required.