Celldex shares plunge 13% despite positive urticaria trial results as safety concerns weigh

Celldex shares plunged on the 22nd (local time). Despite successful clinical trials of its treatment for chronic urticaria, investors focused on safety concerns after life-threatening cases of anaphylaxis were identified.

According to BioPharma Dive on the 22nd (local time), Celldex shares fell 13% in early trading. The company announced successful results from two phase 3 trials of barzolvolimab in patients with chronic spontaneous urticaria.

Chronic spontaneous urticaria is a condition that causes hives, severe itching, burning and swelling. However, some investors focused on two cases of anaphylaxis identified among patients who received barzolvolimab.

Celldex downplayed the safety concerns. Anthony Marucci, CEO, said on a conference call that the incidence was “very low” among approximately 2,400 patients treated overall. In a press release, the company said barzolvolimab was well tolerated and demonstrated a favorable safety profile.

Barzolvolimab is Celldex’s key asset as it transitions from an oncology company to an immunology company. The drug works by reducing the number of mast cells involved in urticaria.

Christine Kluska, an analyst at Cantor Fitzgerald, said, “Celldex’s efficacy is the best among the phase 3 data we have seen across all key studies,” and assessed its safety profile as favorable compared with other biologics generating billions of dollars in sales.

Stifel analyst Alex Thompson said the U.S. Food and Drug Administration’s (FDA) response was difficult to predict but that he remained optimistic. He noted that major drugs including Dupixent also carry anaphylaxis warnings and forecast that barzolvolimab would generate “meaningful sales” even if it received a boxed warning.

Kluska projected that the drug’s peak sales could reach $4.8 billion. Celldex is also testing barzolvolimab in three indications beyond chronic spontaneous urticaria.

The two phase 3 trials enrolled approximately 2,000 patients who had not responded adequately to existing antihistamines. Participants were randomly assigned to either the placebo group or one of two barzolvolimab dosing regimens.

After 24 weeks of treatment, the analysis showed that approximately half of the patients who received barzolvolimab achieved a complete response, with their itching and hives completely resolved. The complete response rate in the placebo group was 15% to 18%.

Celldex assessed the results as “unparalleled” for patients with chronic spontaneous urticaria. However, analysts are monitoring the drug’s safety. Concerns have continued to be raised that excessively low neutrophil counts could increase the risk of infection.

The anaphylaxis cases were included in the adverse-event summary. One case occurred after placebo administration, and two occurred in one of the barzolvolimab treatment groups. Kluska said physicians may administer the first dose in a hospital to monitor for potential problems.

Celldex plans to submit barzolvolimab for FDA approval next year.