Celldex Therapeutics, Inc. announced on September 22, 2026, that its two Phase 3 clinical trials, EMBARQ-CSU1 and EMBARQ-CSU2, have met their primary and all key secondary endpoints. The studies evaluated barzolvolimab in patients with chronic spontaneous urticaria (CSU) whose symptoms were inadequately controlled by H1-antihistamines. The trials were randomized, double-blind, placebo-controlled, and global in nature.

The primary endpoint measured the mean change from baseline in the weekly urticaria activity score (UAS7) at Week 12. In both EMBARQ-CSU1 and EMBARQ-CSU2, the 150 mg every 4 weeks and 300 mg every 8 weeks dose groups demonstrated statistically significant improvements versus placebo. The data cutoff for the analysis was September 9, 2026.

The trials enrolled 1,939 patients in total, with 963 patients in EMBARQ-CSU1 and 976 patients in EMBARQ-CSU2. Patients received either barzolvolimab 150 mg every 4 weeks (following a 300 mg loading dose), barzolvolimab 300 mg every 8 weeks (following a 450 mg loading dose), or placebo for 24 weeks. At the 24-week mark, patients on placebo were re-randomized to active treatment.

Key secondary findings included significantly higher rates of Complete Response (UAS7=0) at both 12 and 24 weeks compared to placebo. Specifically, at Week 12, the 150 mg Q4W dose achieved a 42.4% complete response rate in EMBARQ-CSU1 and 45.7% in EMBARQ-CSU2, while the 300 mg Q8W dose achieved 42.1% and 44.0%, respectively. These rates deepened to 49.0% and 54.0% at Week 24 for the 150 mg Q4W dose.

Barzolvolimab was also found to be effective in specific subpopulations. In patients whose CSU was refractory to omalizumab, the 150 mg Q4W dose achieved a 55.3% complete response rate in EMBARQ-CSU1. Additionally, in patients with baseline angioedema activity score (AAS7) greater than zero, the 150 mg Q4W dose achieved a 62.7% complete response rate in EMBARQ-CSU1.

The company reported that barzolvolimab was well-tolerated through the 24-week placebo-controlled period, with a safety profile consistent with prior Phase 2 experience. The Phase 3 trials are ongoing, with treatment continuing through 52 weeks. Celldex plans to submit a Biologics License Application (BLA) to the FDA in 2027 and intends to present the data at an upcoming medical meeting. The company also noted the establishment of a Phase 3b long-term extension study (LTE) for patients who complete the EMBARQ-CSU trials.