Celldex Therapeutics Spotlights Barzolvolimab as Phase III CSU Data Looms After Fast Enrollment

Key Points

• Celldex is developing barzolvolimab as a mast‑cell‑depleting anti‑KIT antibody distinct from IgE/IL‑4/IL‑13 approaches, and Phase II reported rapid, profound and durable CSU responses with complete response rates up to 51% at week 12, 70% at week 52, and 41% maintaining complete response seven months after stopping therapy.
• The Phase III CSU program enrolled ~1,900 patients six months ahead of schedule, is powered to detect a 10‑point UAS7 difference in the omalizumab‑refractory subgroup, and Celldex expects top‑line Phase III CSU results in Q4.
• Celldex finished 2025 with about $518M in cash, completed a $345M financing and says it has cash guidance through 2027, while targeting commercial positioning as both a first‑line advanced therapy for severe/angioedema patients and a potential option for bio‑refractory cases in a market it pegs at roughly $12B peak sales.

Celldex Therapeutics NASDAQ: CLDX executives used an appearance at H.C. Wainwright’s annual Inflammation and Skin Disease Conference to highlight the company’s late-stage plans for barzolvolimab, an anti-KIT monoclonal antibody being developed for chronic urticaria and other inflammatory skin diseases, and to outline upcoming clinical milestones across the pipeline.

Barzolvolimab positioned as mast-cell depleting approach

In response to questions from H.C. Wainwright Managing Director and Senior Healthcare Analyst Joe Pantginis, the company emphasized barzolvolimab’s mechanism of action as a differentiator in urticaria. A company speaker described barzolvolimab as a drug that “blocks the KIT receptor and leads to mast cell depletion,” calling it a “novel mechanism” aimed at mast cells as the “root cause” of the diseases being studied.

The speaker contrasted that approach with other urticaria therapies that target triggers such as IgE or mediators such as IL-4 and IL-13, noting that barzolvolimab is “going for the mast cells itself” and may have a broader effect. Later in the discussion, the company reiterated that omalizumab targets IgE, dupilumab targets IL-4/IL-13, and BTK approaches act downstream of the IgE receptor.

Phase II data: complete response rates and durability highlighted

The company reviewed results from Phase II studies in chronic spontaneous urticaria (CSU) and chronic inducible urticaria (CIndU). In CSU, barzolvolimab was studied in antihistamine-refractory patients, including patients with prior biologics and other advanced therapies, according to the company.

Celldex said it observed “rapid, profound, and durable effects” on urticaria symptoms in CSU, including complete response rates—defined as no itch and no hives—of up to 51% at week 12. With continued therapy to week 52, the company reported complete response rates rising to 70%. After patients stopped therapy for seven months, Celldex said 41% maintained a complete response.

The company also pointed to improvements in angioedema and quality of life endpoints in the CSU study. In inducible urticaria, Celldex said it studied cold urticaria and symptomatic dermographism and saw statistically significant benefits on provocation testing, with more patients achieving negative provocation tests on barzolvolimab versus placebo across both doses studied. Benefits were also described on the Urticaria Control Test and quality of life measures.

Durability was a recurring theme. Celldex said that after 52 weeks of dosing in CSU followed by six months off therapy, patients maintained responses and, when symptoms recurred, returned at a milder level of disease—an observation the company said raises the question of “disease modification.” In CIndU, Celldex described a retreatment design in which patients who recurred after stopping therapy could restart barzolvolimab; the company said retreatment produced “the exact same response” as initial treatment, which it framed as providing flexibility for future real-world use.

Sarah Cavanaugh, Celldex’s Senior Vice President of Corporate Affairs and Administration, added that tryptase—a marker of mast cell burden—appeared to normalize in study participants. She said that when patients’ disease returned, it was “typically also milder in form,” and tryptase levels were “much more normalized” compared to baseline.

Phase III CSU: enrollment, endpoints, and what Celldex will watch

Celldex said its Phase III CSU program enrolled quickly, completing enrollment “six months” ahead of the company’s guidance and “faster than the competitors’ trials,” according to a company speaker. The company described the trials as “very large” and said they are the largest studies conducted in the antihistamine-refractory population, including patients refractory to advanced therapies. Celldex attributed enrollment performance to unmet need, investigator enthusiasm among allergists and dermatologists, operational execution, and a contract research organization with experience in the category.

The primary endpoint in Phase III is the mean change from baseline in Urticaria Activity Score 7 (UAS7), a daily diary measure commonly used in CSU trials. Celldex said the study is 90% powered to detect a 10-point UAS7 difference between placebo and active treatment in the omalizumab-refractory subgroup, and “overpowered” for the broader population.

In discussing how results may be benchmarked beyond statistical significance, the company said it will be looking for outcomes consistent with Phase II, particularly high complete response rates (no itch, no hives). Celldex also highlighted interest in the omalizumab-refractory population as a significant unmet-need segment.

On study design, the company said approximately 1,900 patients were enrolled, with two different barzolvolimab dosing regimens and placebo. The placebo-controlled period runs six months with a 12-week endpoint, followed by 36 additional weeks of active treatment. The company said the Phase III design was kept similar to Phase II, with the “only real difference” being the addition of a loading dose based on Phase II data.

Commercial outlook: diagnosis gaps and potential entry points

Teri Lawver, Celldex’s Senior Vice President and Chief Commercial Officer, told attendees that the company sees “significant headroom for growth” in early urticaria indications. In the U.S., she said approximately 1.8 million people suffer from CSU, but only 32% receive a proper diagnosis, and diagnosis can take “anywhere from seven months to three years.” Lawver said new entrants in the category can create tailwinds by accelerating diagnosis and movement to advanced therapies.

Lawver also cited Celldex’s view that the worldwide market for chronic urticaria advanced therapies—CSU and CIndU—could reach peak sales of $12 billion, “with potential upside.”

She described two initial areas where Celldex believes barzolvolimab could be positioned:

• First-line advanced therapy for patients refractory to background antihistamines who present with severe disease and angioedema. Lawver cited Phase II angioedema results, including 65% angioedema-free at 12 weeks, rising to “almost eight out of 10 patients” at one year, and argued that placebo-adjusted improvements were more than double historical therapies. She also noted that patients with angioedema have historically been treated with chronic oral corticosteroids, which she characterized as toxic.
• Second-line and later advanced therapy for patients who remain symptomatic after trying one of the “current three approved advanced therapies.” Lawver said Celldex believes barzolvolimab could potentially be the first product to demonstrate label efficacy in a bio-refractory population and efficacy regardless of IgE levels.

In discussing competitive dynamics, the company said physicians want multiple treatment options and consider factors such as severity, symptoms, and dosing convenience. Lawver summarized what she said Celldex is hearing as key differentiators: complete response, deepening of response over time, and durability—particularly off-drug durability.

Manufacturing, cash position, and pipeline milestones

On preparedness for a potential launch, the company said it is working with contract manufacturers, plans to enter the market with a prefilled syringe, and is developing an auto-injector for later.

Cavanaugh discussed Celldex’s balance sheet and financing. She said the company ended 2025 with $518 million in the bank and provided cash guidance “through 2027” at that time. Celldex recently completed a financing that brought in an additional $345 million, and Cavanaugh said the company expects to update guidance when it reports first-quarter results. She attributed investor excitement in part to early completion of Phase III enrollment and the expectation for top-line Phase III CSU results in the fourth quarter of the year.

Regarding business development, Cavanaugh said Celldex has been clear it wants to take barzolvolimab forward on its own in the United States, while still evaluating opportunities as appropriate.

On the pipeline, management highlighted CDX-622, a bispecific antibody targeting TSLP and stem cell factor (the ligand for KIT). The company said its Phase I program is fully enrolled, single ascending dose data have been presented and “look very promising,” and multiple ascending dose data are expected later in the year. Celldex also said it has initiated a proof-of-mechanism study in asthma and sees pulmonary diseases as a promising direction, while noting additional earlier-stage work behind CDX-622.

Cavanaugh also outlined upcoming clinical catalysts, including top-line Phase III CSU data in Q4, continued enrollment in a Phase III inducible urticaria study, Phase II prurigo nodularis data expected in summer 2026, Phase II atopic dermatitis data expected in late 2026, and additional CDX-622 multiple ascending dose datasets expected around Q3 2026.

About Celldex Therapeutics NASDAQ: CLDX

Celldex Therapeutics, Inc is a clinical-stage biopharmaceutical company focused on the discovery and development of targeted immunotherapies for cancer and other serious diseases. The company's research platforms leverage novel antibody and vaccine technologies designed to engage the patient's immune system, with a particular emphasis on oncology and neurologic indications. Celldex's pipeline includes both monoclonal antibodies and biologic agents that seek to modulate immune responses or deliver targeted cytotoxic activity.

Among Celldex's lead product candidates is glembatumumab vedotin, an antibody–drug conjugate directed against the glycoprotein NMB (gpNMB) for the treatment of certain breast and skin cancers.

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