A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Multiple-Ascending Doses of Tacabrutideg (BGB-16673) in Adults With Chronic Spontaneous Urticaria and in Healthy Participants

Who can take part

• Part A
• Participants must be diagnosed with chronic spontaneous urticaria (CSU) for ≥ 6 months before randomization
• The presence of itch and hives for ≥6 consecutive weeks at any time prior to randomization despite the use of second-generation H1-antihistamines
• UAS7≥16 and HSS7≥8 during the 7 days before randomization
• Participants must not have had any missing UAS7 entry (ISS7 and HSS7) during the 7 days before randomization
• Presence of hives must have been documented within 3 months before randomization; Part B
• Participants must be 18 to 55 years of age and healthy, with no clinically relevant abnormalities
• Body Mass Index (BMI) of 18 to 32 kg/m\^2; and a total body weight > 50 kg (110 lbs)

Who cannot take part

• Any uncontrolled disease state, including asthma or inflammatory bowel disease where flares are commonly treated with oral or parenteral corticosteroids
• Prior exposure to any BTK inhibitors or protein degraders; NOTE: Other protocol defined Inclusion/Exclusion criteria may apply
• Other diseases with symptoms of urticaria or angioedema
• Any other skin disease associated with chronic itching that might influence in the investigators opinion the study evaluations and results, eg, atopic dermatitis, bullous pemphigoid, dermatitis herpetiformis, senile pruritus, or psoriasis; All Participants
• Significant bleeding risk or coagulopathy
• Part A
• Participants who have a clearly defined, predominating or sole trigger for their chronic urticaria (chronic inducible urticaria), including urticaria factitia (symptomatic dermographism) or cold, heat, solar, pressure, delayed pressure, aquagenic, cholinergic, or contact urticaria