This is a randomized, double-blind, placebo-controlled phase 1b clinical study to evaluate the safety, tolerability, pharmacokinetics and preliminary efficacy of Alpha-0261 Tablets in healthy Chinese adults and in patients with chronic spontaneous urticaria.

Inclusion Criteria:

• Written informed consent must be obtained before any assessment is performed.(Part 1 and Part 2)
• Aged ≥ 18 and ≤ 75, male or female (Part 1).
• Diagnosed with CSU prior to screening at least 6 months. (Part 1)
• Received stable second-generation H1 antihistamine therapy for at least 2 weeks before randomization, and is willing to maintain the stable treatment regimen throughout the study treatment period. (Part 1)
• Aged ≥ 18 and ≤ 55, male or female (Part 2).
• Weight: ≥ 50 kg for males, ≥ 45 kg for females; 19 kg/m2 ≤ body mass index (BMI) ≤ 28 kg/m2. (Part 2)
• In general good health. (Part 2)

Exclusion Criteria:

• Inducible urticaria with identifiable triggers, including dermographism, cold contact urticaria, heat contact urticaria, solar urticaria, pressure urticaria, delayed pressure urticaria, aquagenic urticaria, cholinergic urticaria, or contact urticaria. (Part 1)
• Other chronic pruritic skin diseases that may affect the assessment of study outcomes, such as atopic dermatitis, bullous pemphigoid, dermatitis herpetiformis, senile pruritus, or psoriasis. (Part 1)
• Other conditions that may cause urticaria or angioedema symptoms, including but not limited to urticarial vasculitis, urticaria pigmentosa, erythema multiforme, mastocytosis, hereditary urticaria, or acquired/drug-induced urticaria. (Part 1)
• Have a history of any severe allergic reaction or anaphylaxis. (Part 2)
• Any condition, which in the investigator's opinion might jeopardize articipant's safety or compliance with the protocol. (Part 2)
• Have clinically significant abnormalities on clinical laboratory results. (Part 2)