An Open-label Extension Study to Evaluate the Long-term Safety and Tolerability of LOU064 in Subjects With CSU

Key Inclusion Criteria

• Participants must provide written informed consent prior to any assessments.
• Participants must be willing and able to complete a daily symptom eDiary throughout the study and adhere to the study visit schedules.
• Participants transitioning from the CLOU064A2201 trial must have completed either the Week 12 visit (end of treatment period) or the Week 16 visit (end of follow-up period). They will be assigned to either the treatment period or the observational period based on their UAS7 score (average score from the 7 days prior to the respective visit) as follows:
• Participants transitioning at Week 12 of CLOU064A2201 with a UAS7 score of ≥16 will be allocated to the treatment period.
• Participants transitioning at Week 16 of CLOU064A2201 with a UAS7 score of ≥16 will be allocated to the treatment period.
• Participants transitioning at Week 16 of CLOU064A2201 with a UAS7 score of <16 will be allocated to the observational period.

Key Exclusion Criteria

• Participants with a clearly defined predominant or sole trigger for their chronic urticaria, such as chronic inducible urticaria (including symptomatic dermographism, cold-induced, heat-induced, solar-induced, pressure-induced, delayed pressure-induced, aquagenic-induced, cholinergic-induced, or contact-induced urticaria).
• Participants with other diseases presenting with urticaria or angioedema symptoms, including but not limited to urticaria vasculitis, urticarial pigmentosa, erythema multiforme, mastocytosis, hereditary urticaria, or acquired/drug-induced urticaria.
• Participants with any other skin disease associated with chronic itching that, in the opinion of the investigator, could affect the study evaluations and results, such as atopic dermatitis, bullous pemphigoid, dermatitis herpetiformis, senile pruritus, or psoriasis.
• Participants with a history or current diagnosis of ECG abnormalities that indicate a significant safety risk for their participation in the study, including:
• Concomitant clinically significant cardiac arrhythmias (e.g., sustained ventricular tachycardia) and clinically significant second or third-degree AV block without a pacemaker.
• History of familiar long QT syndrome or a known family history of Torsades de Pointes.
• Resting heart rate (as determined by physical exam or 12-lead ECG) below 50 bpm.
• Resting QTcF interval ≥450 msec (in males) or ≥460 msec (in females) at day 1 of the treatment period or inability to determine the QTcF interval.
• Use of agents known to prolong the QT interval, unless they can be permanently discontinued for the duration of the study.
• Participants with a significant risk of bleeding or coagulation disorders.
• Participants with a known or suspected history of an ongoing, chronic, or recurrent infectious disease, including but not limited to opportunistic infections (e.g., tuberculosis, atypical mycobacterioses, listeriosis, or aspergillosis), HIV, or Hepatitis B/C.