Shares of the New Jersey-based company fell nearly 15% as investors focused on two cases of probable anaphylaxis reported in the studies.
The trials tested two doses of barzolvolimab in patients with chronic spontaneous urticaria, a chronic skin condition marked by recurring hives and swelling whose symptoms are inadequately controlled by allergy medicines.
Two cases of probable anaphylaxis were confirmed following barzolvolimab treatment, the company said. One patient required hospitalisation, while the other was treated at the clinic and discharged.
Investor concerns about the anaphylaxis cases and efficacy were weighing on the shares, Cantor analyst Kristen Kluska said, adding, “the market is hyper-focusing on these points.”
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The company said it expects any barzolvolimab label, if approved, to include warnings and precautions related to hypersensitivity and anaphylaxis, similar to other biologics.
Both trials met the primary endpoint of reducing urticaria activity scores at week 12. At that point, 42.1% to 45.7% of barzolvolimab-treated patients had a complete response, meaning no itching or hives, compared with 9.3% to 12.6% of patients on placebo.Response rates rose to 45.1% to 54% at week 24, versus about 15% to 18% for placebo.
The overall dropout rate was 16%, Celldex Chief Medical Officer Diane Young said in a call with analysts. Hair-color and skin-pigmentation changes were among adverse events leading to discontinuation
The drug also benefited patients whose disease had not responded to omalizumab, sold as Xolair by Novartis and Roche, as well as those with angioedema.
Celldex plans to submit a marketing application to the U.S. FDA in 2027.
In July, Celldex Therapeutics discontinued development of barzolvolimab for patients with prurigo nodularis after it failed to meet the main goal in a mid-stage study.