A Phase 2, Randomized, Double-Blind, Placebo-Controlled, Parallel-Group, Multicenter Study to Assess the Efficacy and Safety of THB335 in Adult Participants With Chronic Spontaneous Urticaria (CSU)

Key Inclusion Criteria: * Males and females 18 through 85 years. * Diagnosis of chronic spontaneous urticaria (CSU) ≥ 6 months. * Active CSU despite treatment with a second-generation H1 antihistamine. * Weekly Urticaria Activity Score (UAS7) ≥ 16 and ISS7 ≥ 8 during the 7 days before randomization, with sufficient electronic diary entries to calculate the baseline scores. * Body mass index of 18 to 38 kg/m² and minimum body weight of 50 kg for male participants or 45 kg for female participants. * Willing and able to complete the daily electronic diary, attend scheduled study visits, and comply with study procedures. * Participants capable of becoming pregnant or producing sperm must agree to follow the protocol-defined contraception requirements. Key Exclusion Criteria: * Chronic urticaria with an identified cause other than chronic spontaneous urticaria. * Another active skin condition associated with chronic itching that could interfere with the study assessments. * Recent treatment with prohibited immunosuppressive therapy, biologic therapy, a Bruton's tyrosine kinase inhibitor, an investigational drug, or another therapy that inhibits the c-KIT receptor. * Clinically significant hepatic, hematologic, or renal disease or laboratory abnormalities. * Active, chronic, or recurrent infection, including human immunodeficiency virus or viral hepatitis infection. * Clinically significant cardiovascular disease or electrocardiogram abnormality, including clinically significant…