24 Weeks Double-blind Randomized Placebo-controlled Trial to Evaluate Efficacy, PK, Safety of LOU064 in Adolescents (12 - <18) With CSU and Inadequate Response to H1-antihistamine Followed by Optional 3 Years Open-label Extension and an Optional 3 Years Safety Long-term Treatment-free Follow-up

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