A Study to Evaluate the Long-term Safety and Efficacy of Fenebrutinib in Participants Previously Enrolled in a Fenebrutinib Chronic Spontaneous Urticaria (CSU) 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