The purpose of this trial is:
1. to assess the efficacy, pharmacokinetics, and safety of remibrutinib vs. placebo in adolescents from 12 to \< 18 years of age suffering from chronic spontaneous urticaria inadequately controlled by H1-antihistamines 2. to collect long-term efficacy, safety and tolerability data on remibrutinib in adolescents after having completed 24 weeks of treatment 3. to collect safety data in this population for up to three years after the last dose of study treatment
Male and female adolescent participants aged >= 12 to < 18 years of age at the time of signing the informed consent
CSU duration for >= 6 months prior to screening (defined as the onset of CSU determined by the investigator based on all available supporting documentation)
The presence of itch and hives for ≥ 6 consecutive weeks prior to screening despite the use of second-generation H1-AH during this time period according to local treatment guidelines
UAS7 score (range 0 - 42) >= 16, ISS7 score (range 0 - 21) >= 6 and HSS7 score (range 0 - 21) >= 6 during the 7 days prior to randomization (Day 1)
Previous use of remibrutinib or other BTK inhibitors
Significant bleeding risk or coagulation disorders
History of gastrointestinal bleeding
Requirement for anti-platelet medication, except for acetylsalicylic acid up to 100 mg/d or clopidogrel up to 75 mg/d. The use of dual anti-platelet therapy (e.g., acetylsalicylic acid + clopidogrel) is prohibited