Trial 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.