Celldex Therapeutics (Celldex (CLDX)) is pulling the plug on its Phase 2 trial of barzolvolimab for prurigo nodularis, a chronic skin condition that causes intensely itchy nodules. The company said Tuesday that the drug failed to achieve its primary and key secondary goals, and the study is being discontinued.
The 24-week, double-blind, placebo-controlled trial enrolled 140 patients with moderate to severe symptoms who hadn't responded well to topical treatments. The main goal was to see a four-point or greater improvement on the worst itch numeric rating scale at 12 weeks. But the percentage of patients hitting that mark wasn't meaningfully different from the placebo group. Secondary targets, like the investigator global assessment for skin lesions, also flopped. Even extending the active treatment and evaluation period to 24 weeks didn't yield any extra clinical benefits.
Barzolvolimab is a novel humanized monoclonal antibody designed to target and deplete mast cells—immune cells thought to drive inflammation and itching. And on that front, it worked: the treatment triggered a rapid, profound, and sustained reduction in circulating tryptase, clearly confirming systemic mast cell depletion. But that biological response didn't translate into symptom relief. Researchers now suspect that mast cells may not be the central pathogenic driver of prurigo nodularis after all.
Despite the lack of efficacy, the drug remained well-tolerated. The dosing regimen—an initial 450mg loading dose followed by 150mg or 300mg every four weeks—maintained a favorable safety profile consistent with earlier studies. After the main phase, patients were monitored for an additional 16 weeks, but the primary investigation is now halted.
This isn't Celldex's first setback with barzolvolimab. In August 2025, the company stopped developing the drug for eosinophilic esophagitis (EoE) after it failed to improve symptoms or endoscopic findings compared to placebo.
Investors reacted swiftly. Celldex shares were down 6.06% at $33.50 in premarket trading on Wednesday, reflecting the market's disappointment with another clinical miss.
