Celldex Therapeutics, Inc. announced new data from the Company's open label Phase 1b clinical trial of barzolvolimab in patients with antihistamine refractory chronic inducible urticarias are being presented at the GA²LEN Global Urticaria Forum (GUF) held in Berlin, Germany. These diseases, which are often severe and debilitating, can significantly impact patients' lives. Barzolvolimab is a humanized monoclonal antibody that binds the receptor tyrosine kinase KIT with high specificity and potently inhibits its activity.

All 9 of 9 (100%) cold urticaria patients who received a 1.5 mg/kg single full dose of barzolvolimab experienced a complete response as assessed by provocation testing, including 4 of 4 patients with omalizumab refractory disease. This cohort was added to the Phase 1b trial in patients with chronic inducible urticaria after Celldex previously reported a 95% complete response rate in July 2021 in patients with antihistamine-refractory cold urticaria and symptomatic dermographism who received a single 3.0 mg/kg dose of barzolvolimab. The Company also added an optional long term follow up evaluation for the initial cohorts of patients treated at 3.0 mg/kg beyond the original 12 week follow up period out to 36 weeks and confirmed that barzolvolimab-induced response and mast cell suppression are durable and linked.

Cold Urticaria 1.5 mg/kg intravenous cohort oral presentation: “Cold urticaria patients achieve complete response with 1.5 mg/kg barzolvolimab” 10 patients received a single intravenous infusion of barzolvolimab at 1.5 mg/kg. Patients had high disease activity as assessed by provocation threshold testing with a mean baseline critical temperature threshold of 18.4°C or 65°F with a range from 6 to 27°C or 43 to 81°F. All patients had disease refractory to antihistamines and five patients had disease refractory to omalizumab. Safety results are reported for all 10 patients; activity results are reported for the 9 patients who received a full dose of barzolvolimab, including four patients with omalizumab refractory disease.

The Company presented these new 1.5 mg/kg dose cohort data alongside the previously presented 3.0 mg/kg dose cohort to allow for comparison between the dose levels. 21 patients received a single infusion of barzolvolimab at 3.0 mg/kg, including 11 (10 evaluable for activity) patients with cold urticaria and 10 with symptomatic dermographism. Patients had high disease activity as assessed by provocation threshold testing at baseline and poorly controlled disease by UCT.

All patients had disease refractory to antihistamines and three patients had disease refractory to omalizumab. As previously reported, a single 3.0 mg/kg IV dose was generally well tolerated and demonstrated a 95% complete response (negative provocation testing) and 100% well controlled urticaria by Urticaria Control Test (UCT), including in all patients with disease refractory to omalizumab. Profound reduction in serum tryptase and skin mast cells during the 12 week follow up period were observed.

14 patients consented to the optional long term follow up evaluation (6 cold, 8 symptomatic dermographism); 10 of the 14 still had complete control of their disease as assessed by provocation testing at week 12. Data were collected at one or more timepoints beyond week 12 through week 36.