4CPS-144 Safety and effectiveness of reduced dose omalizumab for chronic idiopathic urticaria

Background and importance Omalizumab, a monoclonal antibody that selectively binds to human immunoglobulin E, has been approved by the FDA for the treatment of chronic idiopathic urticaria (CIU) at two different dosing: 150 mg (reduced dose) and 300 mg monthly. Aim and objectives To determine the safety and effectiveness of omalizumab in both doses for the treatment of CIU in our centre. Material and methods This was an observational, descriptive, retrospective study of omalizumab prescribed for adult patients with CIU from January 2015 to September 2019 in a third level hospital. Variables collected were sex, age, service (allergy or dermatology), previous treatments, initial dose, dose change, clinical variable urticaria activity score 7 (UAS7), suspension of treatment and adverse reactions. Results Fifty-two patients (67.31% women) with a median age of 50.5 years (range 23–75) were included: 65.38% (n=34) were from allergy and 34.62% from dermatology. All patients had previously received antihistamines, montelukast and ciclosporin. Only three patients started with a monthly dose of omalizumab of 150 mg while the rest (94.23% (n=49)) started with 300 mg monthly. However, in the last group of patients, 44.90% (n=22) required a dose change: in 68.18% (n=15) of patients, the dose was decreased to 150 mg monthly because of a good response and in the rest (31.82% (n=7)) the dose was intensified due to lack of disease control. UAS7 was collected before and during treatment with omalizumab in only 69.23% of patients (n=36). Median UAS7 before treatment with omalizumab was 29.5 (range 2–42). During treatment, UAS7 was 0 (range 0–32) with both doses of omalizumab. In total, 13.46% (n=7) of patients stopped treatment with omalizumab: 3 patients receiving a dose of 150 mg for improvement in disease, 3 for inefficiency and in 1 the reason was unknown. Adverse reactions occurred in 2 patients: 1 patient had alopecia and asthenia and another patient gained weight. Conclusion and relevance There was a high percentage of patients in our centre who received a dose of omalizumab 300 mg monthly for CIU but a reduced dose (150 mg monthly) was equally effective and safe, even stopping treatment for improvement in CIU which would also have an economic impact. References and/or acknowledgements No conflict of interest.