**6.1 UB-221**

UB-221 is a humanized IgG1 mAb (clone 8D6) that targets the Cε3 domain of IgE antibody and, unlike omalizumab, it can bind to IgE bound by CD23 (**Table 1**). UB-221 neutralizes IgE without activation of mast cells and basophils and was superior to omalizumab while targeting IgE by 3- to 8-folds in terms of pharmacologic effects. It is currently being investigated in two ongoing phase I trials for safety, tolerability, pharmacodynamics, and pharmacokinetics following a single dose (0.2, 0.6, 2, 6, 10 mg/kg UB-221 intravenously vs. placebo) in adult patients with CSU inadequately controlled with H1-antihistamines (NCT03632291 in Taiwan, and NCT04175704, location not provided).
