Barzolvolimab for Chronic Spontaneous Urticaria: Phase 3 Results and Current Options

Your patient has had hives most days for over 8 months. She takes cetirizine 4 times per day, and you added omalizumab in the spring. It helped a bit, but she still wakes up with welts, and lip swelling isn’t unusual for her.

Patients like her may soon have another option: In September 2026, Celldex announced phase 3 results for barzolvolimab, an investigational monoclonal antibody for chronic spontaneous urticaria (CSU). In two large trials, it met every main goal, including in patients who hadn’t responded to omalizumab.

Here’s what you need to know about barzolvoliumab, including how it compares with the treatments you can prescribe today.

1. Overview

Mast cells drive CSU. When they release histamine and other chemicals, the result is itching, hives, and swelling.

Every approved treatment works on one step of that process:

• Antihistamines block histamine after it’s released.

• Omalizumab (Xolair) binds IgE, blocking the antibody that primes mast cells to release.

• Dupilumab (Dupixent) blocks IL-4 and IL-13, two steps in the allergic-type inflammation pathway.

• Remibrutinib (Rhapsido) blocks an enzyme mast cells use to release histamine.

Barzolvolimab works differently. It blocks KIT, a receptor that mast cells need to survive. Without it, mast cells die off.

KIT also sits on pigment cells and hematopoietic stem cells, which explains some of the drug’s unusual side effects (more on that below).

2. Phase 3 data

According to the manufacturer, two trials enrolled over 1,900 adults whose hives persisted despite using antihistamines, some taking them at up to four times the standard dose. About two-thirds of participants had severe disease, and about 1 in 7 had already failed omalizumab.

Patients received placebo or barzolvolimab as an injection under the skin, either every 4 weeks or every 8 weeks. Both schedules worked about equally well.

The results:

• Complete response (no itch, no hives): More than 4 in 10 patients saw a complete response at 12 weeks and about half of patients at 24 weeks. (In the placebo group, it was about 1 in 10, and 1 in 6, respectively).

• Patients who failed omalizumab: About half of these patients were symptom-free at 12 weeks (versus less than 15% on placebo).

• Angioedema: Among patients who experienced swelling, over two-thirds had none at 12 weeks (versus about a third on placebo).

Keep in mind that these are topline results from a company announcement. They haven’t been peer reviewed, and the full data haven’t been presented.

3. Side effects

Barzolvolimab’s side effects included changes to patients’ appearance and neutrophil count, consistent with expected effects of KIT inhibition.

A few things to know about these side effects:

• Most side effects were mild. Serious side effects were no more common than with placebo.

• Low neutrophils didn’t translate to more infections. Infection rates were roughly equal in all groups, including placebo.

• The changes appear to reverse. In a phase 2 trial, hair and skin color changes resolved after patients stopped the drug, and neutrophil counts returned to baseline.

Hair hypopigmentation can occur on the head, face, and body. For some patients, this may be a dealbreaker. Others who’ve had daily hives for years may accept it. It’s important to discuss this possibility before the first dose.

4. Timeline

If you’re wondering when barzolvolimab will be available, here’s the anticipated timeline:

• Clinical trials will continue through 52 weeks, with those results expected in February 2027.

• Celldex plans to file with the FDA in 2027.

• Since a standard FDA review takes about a year, a realistic approval won’t come before 2028.

Both trials enrolled adults only, so approval would likely be limited to adults.

Current treatment options for CSU

Until barzolvoliumab or another treatment option comes to the forefront, treatment for CSU remains unchanged. The international, multi-group urticaria guidelines recommend a step-by-step approach:

1. Start with a second-generation antihistamine (like cetirizine) at the standard dose.

2. If hives persist, increase it up to four times the standard dose. Don’t go higher.

3. If that fails, add omalizumab. Dupilumab or remibrutinib are other options.

4. Consider cyclosporine if those options don’t work.

5. Oral steroids in a short course may be considered for severe exacerbation, but should otherwise be avoided.

Frequently asked questions

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Written by:

Farzon A. Nahvi, MD

Farzon Nahvi, MD, is an emergency medicine physician and author of “Code Gray: Death, Life, and Uncertainty in the ER.” He works at Concord Hospital in Concord, New Hampshire, and teaches at the Geisel School of Medicine at Dartmouth.

Edited by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined clinical medicine with her passion for education and content development for many years. She is co-executive director at Nonclinical Physicians Network and has served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

Reviewed by:

Maria Robinson, MD, MBA

Maria Robinson, MD, MBA, is a board-certified dermatologist and dermatopathologist who has practiced dermatology and dermatopathology for over 10 years across private practice, academic, and telehealth settings. She is a fellow of the American Academy of Dermatology and the American Society of Dermatopathology.

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