Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of UB-221 as an Add-on Therapy in CSU Patients

Inclusion Criteria: * Subjects with age between 20 to 65 years old (inclusive). * Subjects who are able and willing to provide the informed consent. * Male subjects with body weight of 50 kilogram (kg) or above; female subjects body weight of 45 kilogram (kg) or above. * Subjects diagnosed with chronic spontaneous urticaria (CSU). Exclusion Criteria: * History of significant diseases (other than CSU) or major clinical conditions by the investigator's judgment, such as auto-immune disease or psychiatric and behavioral conditions from which the investigator considers the subject is not suitable to participate in this study.