Biopredictors for Omalizumab Response in Patients With Chronic Spontaneous Urticaria

Proposed negative biopredictors of omalizumab response in patients with chronic spontaneous urticaria are low baseline IgE (≤40 IU/mL), positive CU Index (CUI) test result, and basopenia defined by blood histamine content (BHC) (≤8 ng/mL).

To test the hypothesis that patients with these negative biopredictors will have a poorer response to omalizumab.

We performed a retrospective analysis of 3 phase III studies of antihistamine-refractory subjects with chronic spontaneous urticaria who received omalizumab 300 mg every 4 weeks for 12 weeks. The relationship between baseline biopredictors and subjects with excellent symptom control measured by Urticaria Activity Score over 7 days (UAS7 ≤ 6) or poor symptom control (UAS7 > 6) after 12 weeks was examined. We performed χ², logistic regression, and receiver-operating characteristic analysis.

In 363 subjects, data were available for IgE and CUI; 266 had BHC measures. Subjects with UAS7 higher than 6 at 12 weeks significantly more often expressed a baseline negative biopredictor: IgE level less than or equal to 40 IU/mL (n = 109 [50%]) versus IgE level more than 40 IU/mL (n = 239 [33%]); CUI positive (n = 98 [55%]) versus negative (n = 263 [32%]); BHC less than 8 ng/mL (n = 64 [55%]) versus BHC more than 8 ng/mL (n = 202 [33%]). CUI positivity significantly predicted a UAS7 higher than 6 at 12 weeks (P = .0002; odds ratio, 2.54; 95% CI, 1.55-4.15). According to receiver-operating characteristic curve analysis, a BHC of 6.4 ng/mL was distinguishing nonresponders from responders. Among subjects with low baseline IgE, the presence of low BHC was predictive for nonresponsiveness to omalizumab (χ² = 4.215; P = .040).

Subjects with positive CUI, low BHC, or both low IgE and BHC have an increased likelihood of poorer response to omalizumab at 12 weeks.