This trial consists of 3 different periods: 1/ the core period, which is randomized and double-blind, during which 2/3 participants will receive remibrutinib and 1/3 will receive placebo for 12 weeks. After 12 weeks, all participants will receive remibrutinib for an additional 12 weeks. Total duration: approximately 34 weeks (10 site visits).~2/ an optional open-label extension period proposed to all participants who received remibrutinib for at least 4 months in the core period. Depending on their CSU symptoms (as assessed by the doctor), participants will either receive remibrutinib for 24 weeks, or enter an observational treatment-free period for 1 year. If the CSU symptoms return during the observational period, the participants can switch to the treatment period at any time (decided by the doctor). At the end of the 24-week treatment period, if CSU is controlled, participants will enter the 1-year observational period, otherwise, they can continue with another cycle of 24-week remibrutinib treatment. The number of remibrutinib treatment or observational cycles will be limited to 3 times each. Total duration: from 1 year to approximately 3 years, and number of visits: from 3 to 10 (depending on the CSU symptoms).~3/ an optional long-term treatment-free follow-up period proposed to all participants who completed at least 4 months treatment in the core period. No treatment will be given. Duration: 3 years with 1 site visit and up to 5 phone call follow-up visits.~The primary clinical question of interest is what is the effect of remibrutinib treatment versus placebo on the change from baseline in UAS7, ISS7 and HSS7 scores after 12 weeks of treatment
The purpose of this trial is:~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~to collect long-term efficacy, safety and tolerability data on remibrutinib in adolescents after having completed 24 weeks of treatment~to collect safety data in this population for up to three years after the last dose of treatment