Trial of JYB1904 Injection in Adult Patients With Chronic Spontaneous Urticaria.

This Phase III Trial is Meant to Evaluate the Efficacy, and Safety of JYB1904 Injection in Adult Patients With Chronic Spontaneous Urticaria.

Inclusion Criteria: * Male or female participant must be ≥18 years old at the time of signing the informed consent. * Participants are diagnosed with CSU for ≥6 months before screening. * Participants suffer from itching and hives for at least 6 consecutive weeks at any time before screening. * UAS7 (range 0\~42) ≥16, ISS7 (range 0\~21) ≥8 during 7 days before randomization. * Participants treated with stable dose of second-generation H1 antihistamines (up to 4x approved dose) for at least 6 consecutive weeks before randomization, switching medications, or changing drug dosage or frequency is not allowed within 3 weeks before randomization. * Participants have ≥6 days record of UAS7 before randomization. Exclusion Criteria: * Participants who suffer from inducible urticaria with definite inducements, including urticaria factitia (dermatographism), cold contact, heat contact, solar, pressure, delayed pressure, aquagenic, cholinergic or contact urticaria, etc. * Participants who suffer from any other skin diseases with chronic itching, such as atopic dermatitis, bullous pemphigoid, dermatitis herpetiformis, senile pruritus or psoriasis, etc. * Participants who suffer from other diseases with symptoms of urticaria or angioedema, including but not limited to urticaria vasculitis, urticaria pigmentosa, erythema multiforme, mastocytosis, hereditary urticaria or acquired/drug-induced urticaria. * Participants who are contraindicated or hypersensitive to antihistamines or any of its component (such as fexofenadine, loratadine, desloratadine, cetirizine, levocetirizine, rupatadine, bilastine). * History of anaphylactic shock.