Omalizumab (Xolair) is a biologic treatment for chronic spontaneous urticaria (CSU) when antihistamines fail. However, up to 40% may not respond optimally. A new retrospective analysis of phase III trials offers clues to identify those at higher risk of poorer response early on.
Researchers examined data from nearly 400 antihistamine-refractory CSU patients treated with omalizumab 300 mg every 4 weeks for 3 months. They focused on 3 proposed negative biopredictors at baseline:
- Low total IgE (≤40 IU/mL)
- Positive CU Index (CUI) test (indicating functional autoantibodies)
- Basopenia, measured by low blood histamine content (BHC ≤8 ng/mL)
Positive CUI emerged as a strong independent predictor (odds ratio 2.54, P=0.0002). For BHC, a cutoff of 6.4 ng/mL best distinguished responders from non-responders via ROC analysis.
In summary, patients with positive CUI, low BHC, or the combination of low IgE + low BHC face a higher likelihood of suboptimal response to omalizumab by week 12.
These biopredictors - available through routine or specialized lab tests - could help clinicians set realistic expectations, consider earlier escalation to alternative therapies, or personalize CSU management. While omalizumab remains highly effective overall, identifying potential slower or poorer responders upfront may improve care efficiency.
This reinforces growing evidence that autoimmune/inflammatory CSU subtypes (often linked to basopenia, autoantibodies, and low IgE) behave differently with anti-IgE therapy. More prospective validation is needed, but these findings add practical tools for everyday allergy and dermatology practice.
References:
https://www.jaci-inpractice.org/article/S2213-2198(25)01134-1/fulltext