Background: Omalizumab, an anti-IgE monoclonal antibody, is an effective treatment for patients with chronic spontaneous urticaria (CSU) resistant to antihistamines, but about 10% are unresponsive. Our aim was to assess the effectiveness, safety, and drug survival (DS) of omalizumab by considering clinical and laboratory characteristics. Methods: We conducted a retrospective study on 296 patients with severe CSU treated with omalizumab. Disease activity, comorbidities, and serum levels of total IgE and anti-thyroid autoantibodies were evaluated over a period of up to 8 years. DS was analyzed using unadjusted Kaplan–Meier survival curves. When applicable, the risk of discontinuation was assessed using Cox regression analysis. Results: Out of 296 patients, 118 (40.4%) were early responders, 72 (25.0%) were late responders, 76 (26.0%) were partial responders, and 25 (8.6%) were non-responders. Early responders were more likely to be patients without associated inducible urticaria (p = 0.021, χ² = 9.692), without autoimmune thyroiditis (p = 0.007, χ² = 12.037), and those with higher IgE levels (p = 0.039, χ² = 8.385). Overall, DS was 53.5% at 8 years, primarily due to clinical remission. DS due to inefficacy and clinical remission were 83.9% and 62.1%, respectively, at 8 years. No patients discontinued omalizumab due to adverse events. Patients with normal IgE levels (p = 0.012, HR = 4.639, CI: 1.393–15.445) and those with autoimmune thyroiditis (p = 0.028, HR = 3.316, CI: 1.128–8.718) had a higher risk of discontinuing omalizumab due to inefficacy. Conclusions: This study confirms the long-term effectiveness and safety of omalizumab in the treatment of CSU over a period of up to 8 years. Most patients discontinued omalizumab due to clinical remission, while only 5.1% discontinued it due to ineffectiveness.

Atopic dermatitis (AD) profoundly impacts patients' lives, necessitating long-term systemic treatments. This retrospective study involved 709 severe AD patients receiving dupilumab. Drug survival (DS) was analyzed using Kaplan-Meier curves, evaluating reasons for discontinuation. The log-rank test and Cox regression analysis were applied to assess differences in drug survival across baseline clinical characteristic groups. Dupilumab showcased remarkable overall drug survival, reaching 74.1% at 65 months. Survival rates remained robust even when considering discontinuation solely due to primary or secondary inefficacy (86.4% at 65 months). For overall DS, the log-rank test did not reveal a statistically significant difference among the groups. Cox regression analysis showed that patients with nummular eczema-like as a phenotype have an increased risk of discontinuing dupilumab due to the development of psoriasis (p < .001, hazard ratio = 26.15, confidence interval [CI] 6.903-99.016). The multivariate logistic regression analysis confirmed these results (p < .001, OD = 18.956, CI 4.205-85.458), even when considering other clinical and epidemiological characteristics. This investigation establishes dupilumab's enduring efficacy and safety in severe AD, emphasizing its potential as a sustained therapeutic option over 5+ years. Baseline characteristics did not seem to influence DS, with the exception of the nummular eczema-like phenotype, which emerged as a significant predictor of psoriasis occurrence.