Studies Assess Blood Biomarkers for Omalizumab Response in Chronic Spontaneous Urticaria

Intracellular histamine content of basophils did not distinguish among rapid, delayed, and late or no responses to omalizumab in patients with chronic spontaneous urticaria (CSU), while a separate retrospective analysis found that higher baseline monocyte counts, along with preserved basophils and low C-reactive protein, independently predicted complete remission on anti-IgE therapy for CSU. In one study, no statistically significant link was observed between treatment duration and intracellular histamine content per basophil; in the other, baseline monocyte count was the only independent predictor of complete response.

Researchers assessed whether the intracellular histamine content of basophils could serve as a biomarker to predict and monitor response to omalizumab treatment in patients with CSU. A total of 164 adults with CSU with total cellular blood histamine levels measured were included; 106 patients initiated omalizumab treatment, of whom 101 were omalizumab-naive at baseline and were analyzed for treatment response patterns. The investigators classified treatment responses as fast within 1 month, delayed within 3 months, or late after 3 months.

Intracellular histamine content per basophil did not differ among patients with fast response (n = 44), delayed response (n = 36), and late or no response (n = 17) to omalizumab treatment. Histamine content did not significantly differ between patients with a good overall response to treatment (n = 62), a partial response (n = 28), or a poor or no response (n = 7). The study authors wrote that this biomarker is not suitable for predicting omalizumab treatment response, long-term dosing requirements, or drug survival. The research letter was published online on April 26 in Clinical & Experimental Allergy.

The retrospective analysis at a tertiary dermatology center in Turkey evaluated 52 patients with antihistamine-refractory CSU who received omalizumab 300 mg every 4 weeks for at least 12 weeks. Treatment response was assessed using the Urticaria Activity Score over seven days (UAS7), with complete remission strictly defined as a score of 0, indicating total symptom resolution.

At week 12, 11 patients (21.15%) achieved complete remission. Those who achieved complete remission had significantly higher median baseline monocyte levels (0.68 K/µL) compared to non-responders (0.40 K/µL), with strong statistical significance (P = .001). Binary logistic regression analysis confirmed that baseline monocyte count was the only independent predictor of complete response (P = .036).

Complete responders also showed higher baseline basophil counts and lower C-reactive protein levels. Among patients who achieved complete remission, monocyte and neutrophil counts significantly decreased after treatment. Although total IgE levels increased in all patients following treatment, baseline IgE levels did not significantly differ between responders and non-responders.

Both studies noted limitations related to subgroup size or sample size. In the histamine analysis, some of the estimates were based on relatively small subgroups, which may limit their statistical power and precision. In the monocyte analysis, the retrospective design and relatively small sample size resulted in wide confidence intervals in regression analysis, and larger, prospective studies were said to be needed to validate specific monocyte thresholds and confirm the findings. The monocyte study was published in Cureus.