This is a global, multicenter, randomized, double-blind, placebo-controlled, randomized withdrawal Phase 3b extension study, followed by long-term open label treatment cycles to assess the efficacy, safety and tolerability of remibrutinib in adult participants with CSU inadequately controlled by H1-AH. The study comprises 2 Epochs. Epoch 1 is the initial study period for participants who completed preceding remibrutinib Phase 3 studies. Epoch 1 comprises of a 24-week randomized withdrawal period with remibrutinib or placebo for patients with UAS7<16 OR a 24 week Open-label treatment period with remibrutinib for patients with UAS7≥16.~Participants will be randomized in a 1:1 ratio to enter the double-blind placebo-controlled 24-week withdrawal phase. In case of relapse (UAS7≥16) in the blinded group, participants enter the (Re-)treatment period Epoch 1 and receive 24 weeks of Open-label treatment with remibrutinib. At the end of the (Re-)treatment period Epoch 1, participants will move to Epoch 2.~Epoch 2 is the second subsequent study period and consists of 24-week cycles that could either encompass treatment-free Observation and/or Open-label (Re-)treatment periods with remibrutinib, with or without background H1-AH.~In case of relapse (UAS7≥16) during an Observation period, participants enter the next (Re-)treatment period and receive 24 weeks of treatment with remibrutinib. Participants completing an Observation period 2/3/4/5 with a UAS7≤6 will complete the study. Participants with a UAS7 >6 -<16 can enter the next (Re-)treatment period if continuous treatment is considered necessary and beneficial for the individual participant. For participants with a UAS7<16 that enter the next (Re-)treatment period, remibrutinib monotherapy treatment (without background H1-AH) is required.
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 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.