An Extension Study of Long-term Efficacy, Safety and Tolerability of Remibrutinib in Chronic Spontaneous Urticaria Patients Who Completed Preceding Studies With Remibrutinib

This is a Phase 3b multicenter, double-blind, placebo-controlled, randomized withdrawal, and open-label extension study to evaluate the efficacy and safety of remibrutinib 25 mg twice daily (b.i.d.) in adult CSU participants who have completed one of the preceding Phase 3 core studies. The study comprises 2 Epochs: Epoch 1 is the initial study period and includes participants from preceding Phase 3 studies. It consists of a 24-week randomized withdrawal period where participants receive either remibrutinib 25 mg b.i.d. or placebo if their UAS7 score is less than 16. For those with a UAS7 score of 16 or higher, there is a 24-week open-label treatment period with remibrutinib 25 mg b.i.d. Participants are randomized 1:1 to the double-blind placebo-controlled withdrawal phase. All participants will continue their background H1-AH treatment. If participants relapse (UAS7 ≥ 16) in the blinded group, they enter the (Re-)treatment period of Epoch 1 and receive 24 weeks of open-label treatment with remibrutinib 25 mg b.i.d. After this period, they move to Epoch 2. Epoch 2 is the second subsequent study period and consists of 24-week cycles that may include treatment-free observation and/or open-label (Re-)treatment periods with remibrutinib 25 mg b.i.d., with or without background H1-AH, at the investigator's discretion. Participants from future Phase 3 remibrutinib studies may also join Epoch 2 if approved. If participants relapse (UAS7 ≥ 16) during an observation period, they enter the next (Re-)treatment period for 24 weeks of treatment with remibrutinib 25 mg b.i.d. Participants completing an observation period with a UAS7 ≤ 6 will complete the study with an end-of-study (EOS) visit. Those with a UAS7 \> 6 but \< 16 can enter the next (Re-)treatment period if continuous treatment is deemed necessary. Participants with a UAS7 \< 16 in the previous treatment period will receive remibrutinib monotherapy (without background H1-AH). If treatment continuation is not necessary, they complete the EOS visit and leave the study. Participants with a UAS7 ≥ 16 during the observation period will enter the corresponding (Re-)treatment period to continue treatment. Throughout Epoch 2, the use of background H1-AH is at the investigator's discretion, except for participants with a UAS7 \< 16 in the previous treatment period, who will be treated with remibrutinib monotherapy.