Celldex Therapeutics shares fell more than 7% in extended trading Tuesday after its experimental drug barzolvolimab failed a Phase 2 study in prurigo nodularis. The company will discontinue the program but remains focused on developing barzolvolimab for other inflammatory conditions, with Phase 3 CSU data expected in September or October 2026.
Celldex Therapeutics shares fell more than 7% in extended trading Tuesday after its experimental drug barzolvolimab failed a Phase 2 study in prurigo nodularis.
"It is disappointing that this study did not confirm the promising signal we observed in the intravenous Phase 1b trial," Anthony Marucci, co-founder, president and chief executive officer of Celldex, said in a statement.
The study enrolled 140 patients with moderate to severe prurigo nodularis, a chronic skin disease that causes hard, intensely itchy lumps and nodules. Neither the primary endpoint — the proportion of patients achieving at least a four-point improvement in itch severity at Week 12 — nor key secondary goals were met across the two dosing arms compared with placebo. Barzolvolimab was administered subcutaneously at 150 milligrams every four weeks or 300 milligrams every four weeks, each after a 450-milligram loading dose.
The failure marks a setback for Celldex, as barzolvolimab is the company's lead drug candidate and its most advanced pipeline asset. The drug sharply reduced mast cells — immune cells involved in allergic reactions — as measured by serum tryptase levels, but patients reported no meaningful improvement in itch or skin lesions. Celldex said the result suggests mast cells may not be a primary driver of prurigo nodularis, a disease where treatment options have expanded in recent years with Sanofi's blockbuster Dupixent and Galderma's Nemluvio.
The company said it will discontinue the prurigo nodularis program but remains focused on developing barzolvolimab for other inflammatory and allergic conditions. Barzolvolimab has shown positive Phase 2 proof-of-concept data in chronic spontaneous urticaria, symptomatic dermographism and cold urticaria, all of which have advanced to Phase 3. Celldex expects to report late-stage data in chronic spontaneous urticaria in September or October 2026, with mid-stage data in atopic dermatitis due later this year.
The after-hours decline puts Celldex shares at their lowest level since the company reported positive CSU data earlier this year. Investors will watch for the upcoming Phase 3 CSU readout, the next major data event for barzolvolimab's broader development program.
This article is for informational purposes only and does not constitute investment advice.
