Recruitment was stopped after an interim analysis of the parent GS39684 study.

This is a Phase II, multicenter, open-label extension (OLE) study to evaluate the long-term safety and efficacy of fenebrutinib in participants with Chronic Spontaneous Urticaria (CSU) who have completed the treatment period in a fenebrutinib CSU parent study. Participants may enroll in this OLE study at any time after completing the treatment period of the parent study. Participants will receive open-label fenebrutinib at a dose of 200 milligram (mg) orally twice a day. Treatment may continue until the end of the study.

Inclusion Criteria:

• Ability to comply with the study protocol, in the investigator's judgment
• Completion of the treatment period as specified in the parent study
• Acceptable demonstration of tolerance to study drug during the parent study as determined by the investigator or Medical Monitor
• For participants receiving treatment with proton-pump inhibitors (PPIs) or H2-receptor antagonists (H2RAs), agreement to maintain treatment at a stable dose for the first 12 weeks of the study
• For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive measures, and agreement to refrain from donating eggs
• For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use a condom, and agreement to refrain from donating sperm

Exclusion Criteria

• Pregnant or breastfeeding, or intending to become pregnant during the study or within 4 weeks after the final dose of fenebrutinib
• Treatment with any investigational agent or live/attenuated vaccine in the preceding 6 weeks
• Any signs or symptoms of infection judged by the investigator to be clinically significant since completing the treatment period of the parent study
• Any significant changes (e.g., events, changes in medication) occurring after completion of participation in the parent study that, in the investigator's judgment, would increase the risk of adverse events in this OLE study

Qualified researchers may request access to individual patient level data through the clinical study data request platform (www.vivli.org). Further details on Roche's criteria for eligible studies are available here (https://vivli.org/ourmember/roche/). For further details on Roche's Global Policy on the Sharing of Clinical Information and how to request access to related clinical study documents, see here (https://www.roche.com/research\_and\_development/who\_we\_are\_how\_we\_work/clinical\_trials/our\_commitment\_to\_data\_sharing.htm).

The Study being conducted under this Agreement is part of the Overall Study. Investigator is free to publish in reputable journals or to present at professional conferences the results of the Study, but only after the first publication or presentation that involves the Overall Study. The Sponsor may request that Confidential Information be deleted and/or the publication be postponed in order to protect the Sponsor's intellectual property rights.