Study of Remibrutinib (LOU064) Efficacy and Safety and Exploration of Its Mechanism of Action in Participants With Chronic Urticaria

Inclusion Criteria: 1. Signed informed consent must be obtained prior to participation in the study. 2. Male and female participants ≥ 18 years of age at the time of signing of the informed consent forms. 3. CINDU patients: Confirmed diagnosis of CINDU with a duration of ≥ 4 months (defined as onset of CINDU with supporting documentation (e.g. medical record, clinical history, photographs) and inadequate control with H1-AH at local label approved doses at the time of randomization. The response to the provocation test for each CINDU subtype is required before randomization (either during screening or prior to randomization on Day 1): 4. CINDU patients: Patients should be symptomatic for their most bothersome symptom as assessed with the USDD during baseline with a NRS score of 3 or more 5. CSU patients: Diagnosis of CSU (acc. to Zuberbier et al 2022c) not adequately controlled with H1-AH at approved doses alone for at least 4 weeks prior to randomization, as defined by all of the following: * UAS7 score (range 0-42) ≥ 16 and HSS7 (range 0-21) ≥ 8 during 7 days prior to randomization * CSU for ≥ 6 months 6. Participants must be willing and able to attend the protocol defined test procedure throughout the study. Exclusion Criteria: 1. Participants who have a familial/hereditary form (e.g. familial cold autoinflammatory syndrome, familial cold urticaria) of the target CINDU that is being considered for the participant's inclusion in this study. 2. Diseases, other than CSU or CINDU, with urticaria or angioedema symptoms including but not limited to: * urticarial vasculitis, erythema multiforme, cutaneous mastocytosis (urticaria pigmentosa), * food allergies yielding urticaria symptoms when the allergen is not avoided by the dietary habits of the participant * hereditary or acquired angioedema. 3. CINDU patients only: To prevent any confounding effect of CSU symptoms, the CINDU study population will consist of participants with predominant CINDU and should not have a significant share of CSU symptoms (that might make the assessment of CINDU symptoms difficult) as per the investigator's judgement. 4. CSU patients only: Patients should have no relevant inducible urticaria trigger 5. Any other skin disease associated with chronic itching that might influence, in the investigator's opinion, the study evaluations and results (e.g., atopic dermatitis, bullous pemphigoid, dermatitis herpetiformis, senile pruritus, etc.) or skin diseases associated with only wheals and no itch e.g asymptomatic dermographism 6. Known or suspected ongoing, chronic or recurrent infectious disease including but not limited to opportunistic infections (e.g., tuberculosis, atypical mycobacterioses, listeriosis or aspergillosis) and/or known positivity for Human Immunodeficiency Virus (HIV) infection. 7. Evidence of an ongoing Hepatitis C infection (defined by the detection at screening of Hepatitis C virus antibodies (anti-HCVAb) and hepatitis C ribonucleic acid (HCV-RNA) in participants who are positive for anti-HCVAb) and/or an ongoing Hepatitis B infection (defined by the detection of Hepatitis B virus surface antigen (HBsAg) and/or hepatitis B virus (HBV)-DNA at screening; participants who are positive for anti-hepatitis B core (HBc) antibodies but who are negative for antibodies against HBsAg and HBV-DNA can be included into the study if they agree to monitoring for HBsAg and HBV-DNA reactivation). 8. Major surgery within 8 weeks prior to screening or planned surgery for the duration of the study. 9. Evidence of clinically significant cardiovascular (such as but not limited to myocardial infarction, unstable ischemic heart disease, NYHA Class III/IV left ventricular failure, arrhythmia and uncontrolled hypertension within 12 months prior to Screening), neurological, psychiatric, pulmonary, renal, hepatic, endocrine, metabolic, hematological disorders, gastrointestinal disease or immunodeficiency that, in the investigator's opinion, would compromise the safety of the participant, interfere with the interpretation of the study results or otherwise preclude participation or protocol adherence of the participant. 10. Uncontrolled disease states, such as asthma, or inflammatory bowel disease, or any other disease where flares are commonly treated with oral or parenteral corticosteroids. 11. History of lymphoproliferative disease or any known malignancy or history of malignancy of any organ system within the past 5 years (except for basal cell carcinoma or actinic keratosis that have been treated with no evidence of recurrence in the past 3 months, carcinoma in situ of the cervix or non-invasive malignant colon polyps that have been removed). 12. History or presence of impaired renal function as indicated by clinically significantly abnormal creatinine or BUN values, or abnormal urinary constituents (e.g. proteinuria, hematuria) * Evidence of urinary obstruction, or difficulty in voiding at screening * Evidence of congenital renal abnormalities with known effect on renal function * Calculated eGFR \< 60 mL/min 13. Hematology parameters at screening: * Hemoglobin: \< 10 g/dL * Platelets: \< 100,000/mm3 * Leucocytes: \< 3,000/mm3 * Neutrophils:\< 1,500/mm3 14. History or current hepatic disease including but not limited to acute or chronic hepatitis, cirrhosis or hepatic failure or Aspartate Aminotransferase (AST)/ Alanine Aminotransferase (ALT) levels of more than 1.5 x upper limit of normal (ULN) or International Normalized Ratio (INR) of more than 1.5 at screening 15. Use of other investigational drugs s within 5 half-lives or within 30 days (for small molecules) prior to Screening or until the expected pharmacodynamic (PD) effect has returned to baseline (for biologics), whichever is longer; or longer if required by local regulations 16. Contraindications to or hypersensitivity to remibrutinib (or its excipients or to drugs of similar chemical classes) or other substances