Barzolvolimab demonstrated prolonged clinical benefits in patients with Chronic Spontaneous Urticaria (CSU), according to findings presented at the 2026 American Academy of Allergy, Asthma and Immunology (AAAAI) Annual Meeting.

The Phase II, double-blind, placebo-controlled study enrolled patients with antihistamine-refractory CSU and evaluated treatment with barzolvolimab for up to 52 weeks. Participants were randomised to receive either 150 mg every four weeks or 300 mg every eight weeks. A total of 78 patients completed the 52-week treatment period.

By week 52, 70.5 percent of participants achieved at least well-controlled disease, defined as a Urticaria Activity Score over 7 days (UAS7) of 6 or lower. In an exploratory subgroup analysis of 48 patients who had UAS7 scores below 6 at week 52 and available data at week 76, 87.3 percent achieved a complete response at week 52, while 12.7 percent had well-controlled disease. At study entry, 70.9 percent of these patients had severe disease.

28 weeks after the last dose, 50 percent of participants maintained a complete response and 18.8 percent had well-controlled disease. Overall, 81 percent had no more than mild disease activity at week 76. Notably, sustained efficacy was observed despite clearance of the drug and normalisation of serum tryptase levels, a biomarker of mast cell activity.

Quality-of-life measures also reflected durable benefits. At week 76, half of the participants maintained continuous well-controlled disease, with a mean UAS7 score of 0.4. The mean Dermatology Life Quality Index (DLQI) score was 1.17, and 83.3 percent of patients reported no impact of disease on quality of life.

According to lead investigator Dr. Martin Metz of Charité- Universitätsmedizin Berlin, the findings suggest that barzolvolimab’s mechanism of targeting mast cells, the underlying driver of CSU, may contribute to rapid, deep and sustained responses, raising the possibility of a disease-modifying effect.

Researchers noted that the prolonged off-treatment efficacy observed 28 weeks after the final dose supports further investigation of barzolvolimab as a potential long-term treatment option for CSU.