The purpose of this extension study is to collect long-term efficacy, safety and tolerability data on remibrutinib in a selected group of participants with Chronic Spontaneous Urticaria (CSU) who previously completed the treatment phase of remibrutinib preceding Phase 3 core studies. This study will also fulfill the Novartis commitment to provide post-trial access to participants who have completed the preceding Phase 3 studies, where applicable.