Celldex Announces Initial Positive Results from Phase 1 Trial of CDX-622 Demonstrating Favorable Safety and PK Profile and Sustained Mast Cell Inhibition

Core Insights - Celldex announced positive data from the Phase 1 study of CDX-622, a bispecific antibody targeting inflammation and fibrosis pathways [1][2] - The study demonstrated good tolerability, a favorable pharmacokinetic profile, and significant reductions in serum tryptase levels, indicating effective mast cell inhibition [1][6] - The company plans to advance the study to the next phase, testing multiple ascending doses and initiating a Phase 1b study in asthma patients [2][4] Study Design and Results - The Phase 1 trial is a randomized, double-blind, placebo-controlled, dose escalation study assessing safety, pharmacokinetics, pharmacodynamics, and immunogenicity of CDX-622 [4][7] - Part 1 enrolled 32 participants across 4 cohorts, receiving single ascending intravenous doses of CDX-622 (0.3, 1.0, 3.0, and 9.0 mg/kg) over a 12-week observation period [4][6] - Data from Part 1 were presented, and enrollment for Part 2 is ongoing, with results from Parts 2 and 3 expected in Q3 2026 [4][6] Mechanism and Therapeutic Potential - CDX-622 targets two validated pathways: neutralizing TSLP and depleting mast cells via SCF starvation, potentially offering enhanced therapeutic benefits for inflammatory and fibrotic disorders [5][6] - The antibody showed a serum half-life of approximately 18 days at 9 mg/kg, with no evidence of immunogenicity or dose-limiting toxicities observed [6][2] - A single dose led to a rapid and sustained decrease of about 50% in circulating tryptase, consistent with systemic mast cell inhibition [6]