A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, Immunogenicity, Pharmacodynamics and Clinical Activity of BBT001 Following Intravenous Administration in Participants With Chronic Spontaneous Urticaria (CSU)

The study consists of below cohorts:

Cohort A1 (biologic-naïve): 450 mg BBT001 (n = 8) or placebo (n = 4) Cohort A2 (biologic-experienced): 450 mg BBT001 (n = 8) or placebo (n = 4) Cohort A3 (biologic-naïve) (optional): 900 mg BBT001 (n = 8) or placebo (n = 4) Cohort A4 (biologic-experienced) (optional): 900 mg BBT001 (n = 8) or placebo (n = 4)

Inclusion criteria

key inclusion criteria: 1)Male or female 18 to 75 years (inclusive) of age at time of consent. 2)Capped weight to be no more than 125 kg at screening.3)UAS7>=16; 4)Patients must have been on daily stable doses of H1-AH;5) Written informed consent obtained from the participant prior to performing any protocol-related procedures. For A2/A4 only: Participants who have received prior treatment with any biological products (e.g., omalizumab or dupilumab) . The last dose≥ 5 half-lives prior to randomization.

Exclusion criteria

key exclusion criteria: 1）Inducible urticaria ; 2） Diseases with possible symptoms of urticaria or angioedema such as urticarial vasculitis, erythema multiforme, cutaneous mastocytosis ；3） Presence of skin morbidities other than CSU that may interfere with the assessment of the study outcomes; 4)History of herpes simplex infection; 5 ）Serological abnormalities of infection at screening .

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