Celldex shares drop 18% after it follows Allakos’ footsteps in eosinophilic esophagitis

Celldex ends development of barzolvolimab for eosinophilic esophagitis (EoE) after a phase 2 trial met its biological endpoint (mast cell depletion) but failed to improve symptoms like difficulty swallowing.

Why it matters: The decision highlights ongoing challenges in treating EoE, where multiple drugs have shown strong biological effects but no meaningful symptom relief. Investors reacted sharply, pushing shares down 18%.

Backstory:

• EoE is a chronic inflammatory condition of the esophagus driven by white blood cells (eosinophils and mast cells).

• Allakos’ similar drug, lirentelimab, also reduced eosinophils but failed to improve swallowing.

• Celldex randomized 65 patients to receive the anti-KIT antibody barzolvolimab; while the drug significantly reduced mucosal mast cells, it did not improve dysphagia scores or endoscopic inflammation measures.

Big picture: Celldex’s setback thins the pipeline for EoE treatments, leaving Amgen and AstraZeneca’s Tezspire as one of the few late-stage programs. Still, the finding that barzolvolimab depletes mucosal mast cells could unlock new uses for KIT inhibitors in gastrointestinal diseases.

What´s next?:

• The company will continue barzolvolimab studies in skin conditions, including phase 3 trials for chronic spontaneous urticaria and phase 2 trials for atopic dermatitis and prurigo nodularis.

• Future GI strategies may involve Celldex’s bispecific antibody approach to address diseases where mast cell depletion alone isn’t enough.