This study is looking at how well a drug called remibrutinib works for adults with a condition called CINDU, which is a skin problem causing itchy hives not controlled by H1-antihistamines (H1-AHs). The study lasts about 60 weeks and is divided into two main parts: the Core period and the Open-label Extension (OLE).

In the Core period, there are several stages:

• Screening (up to 4 weeks): Doctors check if you can join.
• Double-blind treatment (24 weeks): You’ll get either remibrutinib or a placebo, but won't know which.
• Open-label treatment (28 weeks): All get remibrutinib.
• Follow-up (4 weeks): No treatment, but doctors check on you.

If you still have symptoms after the Core period, you may join the OLE, which could last up to 3 years. Here, you may receive remibrutinib if you need it. To join, you must be 18 or older, have CINDU for at least 4 months, and not have taken remibrutinib before.

• Length: Up to 60 weeks for Core, plus 3 years for OLE.
• Visits: Regular visits required for check-ups.
• Risk: Unknown effects of remibrutinib.