Celldex's barzolvolimab fails Phase 2 prurigo nodularis trial despite mast cell wipeout
The KIT antibody drove profound tryptase reductions in 140 patients but did not separate from placebo on itch or skin lesions, and Celldex is stopping the program in this indication.
Executive Summary
- A Phase 2 trial of Celldex Therapeutics' barzolvolimab in prurigo nodularis missed its primary itch-reduction endpoint and its key secondary endpoints, and the company is stopping the program in this indication.
- The drug achieved its intended pharmacological effect, depleting mast cells as measured by tryptase, but that effect did not translate into fewer itch symptoms or clearer skin, separating a biomarker response from a clinical one.
- Safety held up as expected from prior studies, and the company is directing attention to its Phase 3 chronic urticaria trials, where the same drug has already shown clinical benefit, reframing prurigo nodularis as a mechanism-specific miss rather than a drug-wide setback.
- The failure removes the only KIT-targeted therapy under investigation in prurigo nodularis, leaving the field's more advanced Phase 3 programs built on different mechanisms to define the standard of care in this indication.
The result
Celldex Therapeutics said its Phase 2 study of barzolvolimab in prurigo nodularis (PN) did not meet its primary endpoint, the proportion of patients achieving a four-point or greater improvement on the Worst Itch Numeric Rating Scale (WI-NRS) from baseline to Week 12, or its key secondary endpoints. The percentage of patients with at least a four-point WI-NRS improvement did not differentiate from placebo, and neither did the proportion reaching an Investigator's Global Assessment for Chronic Nodular Prurigo score of 0 or 1. Extending treatment to Week 24 produced no additional improvement. Celldex is discontinuing the Phase 2 study in PN based on these results. NCT06366750+1A Study of Barzolvolimab in Patients With Prurigo NodularisNCT06366750Celldex Reports Results from Phase 2 Study of Barzolvolimab in Prurigo NodularisJul 21, 2026
Probability of SuccessBased on the AppliedXL Probability of Success model. For more information about the methodology, read the research here.
What the drug did do
Barzolvolimab is a humanized monoclonal antibody that binds the KIT receptor and inhibits mast cell survival and activity. In this trial, it produced what Celldex called profound and sustained reductions in circulating tryptase, a marker of systemic mast cell depletion, with the effect appearing early after a 450mg loading dose and holding through the treatment period. Anthony Marucci, Celldex's co-founder, president and chief executive officer, said the tryptase reductions "did not result in improvement of PN symptoms for patients who greatly need effective treatments," and called the outcome disappointing given that the same mechanism had produced "unequivocal Phase 2 proof-of-concept data" in chronic spontaneous urticaria, symptomatic dermographism and cold urticaria. Celldex's own framing in the release states that the disconnect between tryptase reduction and symptom relief indicates mast cells may not be a key pathogenic driver of PN symptoms. Celldex+1Celldex Reports Third Quarter 2025 Financial Results and Provides Corporate UpdateNov 10, 2025Celldex Reports Results from Phase 2 Study of Barzolvolimab in Prurigo NodularisJul 21, 2026
Trial design
The study was a randomized, double-blind, placebo-controlled, parallel-group trial that enrolled 140 adults with moderate to severe PN who had an inadequate response to topical medications. Patients received barzolvolimab at 150mg or 300mg every four weeks after an initial 450mg loading dose, or placebo, delivered subcutaneously. Enrollment held at its target of 140, and the operational model treats that as a routine outcome rather than a shortfall. Barzolvolimab was well tolerated, with a safety profile consistent with prior studies at both dose levels. NCT06366750+1A Study of Barzolvolimab in Patients With Prurigo NodularisNCT06366750Celldex Reports Results from Phase 2 Study of Barzolvolimab in Prurigo NodularisJul 21, 2026
The competitive frame
Barzolvolimab was the only KIT-targeted antibody in clinical testing for prurigo nodularis; the trial's closest comparators by target and mechanism, Celldex's own Phase 3 chronic spontaneous urticaria program and Blueprint Medicines Corporation's BLU-808 and Jasper Therapeutics' briquilimab, are all tested in urticaria indications rather than PN. Within PN itself, the more advanced programs run on different biology: Galderma R&D's nemolizumab (IL-31RA), Sanofi's dupilumab (IL-4Rα) and Incyte Corporation's povorcitinib (JAK1) are each in Phase 3 testing in this indication. That leaves PN's field of Phase 3 candidates unified by targeting itch-signaling or inflammatory pathways rather than the mast cell directly, and this readout is evidence against extending mast cell depletion as a validated mechanism into PN.
What continues
The company's regulatory plans center on programs unaffected by this result: Phase 3 topline data in chronic spontaneous urticaria are expected in September or October 2026, enrollment in Phase 3 cold urticaria and symptomatic dermographism trials is continuing, and Phase 2 topline data in atopic dermatitis are expected later in 2026. Those readouts, not this one, will be the next test of whether barzolvolimab's mast cell mechanism translates into symptom relief in indications where prior Phase 2 data already showed clinical benefit. Celldex+1Celldex Reports Results from Phase 2 Study of Barzolvolimab in Prurigo NodularisJul 21, 2026Celldex Reports Third Quarter 2025 Financial Results and Provides Corporate UpdateNov 10, 2025
This analysis was produced using AI-assisted reporting systems, AppliedXL data, and official public records. These systems undergo editorial review, quality checks, and regular audits by human experts. Errors may still occur, as with any automated system. Always consult the linked primary sources. Read our AI Editorial Policy.