Study to Investigate the Efficacy and Safety of QGE031 in Adolescent Patients With Chronic Spontaneous Urticaria (CSU)

Inclusion Criteria: * Parent or legal guardian's written informed consent and child's assent, if appropriate, must be obtained before any study related activity or assessment is performed. Of note, if the subject reaches age of consent (age as per local law) during the study, they will also need to sign the corresponding study ICF (Informed Consent Form) at the next study visit. * Male and female adolescent patients aged ≥ 12 to \<18 years at the time of screening. * Diagnosis of CSU refractory to approved doses of H1-antihistamines at the time of randomization, as defined by all of the following: * The presence of itch and hives for at least 6 consecutive weeks at any time prior to enrollment despite current use of non-sedating H1-antihistamines during this time period * UAS7 score (range 0 - 42) ≥ 16 and HSS7 (range 0 - 21) ≥ 8 during 7 days prior to randomization (Day 1) * In-clinic UAS ≥ 4 on at least one of the screening visit days or Day 1 or a medical record of the presence of hives (confirmed and documented by a physician); patients must have been on H1-antihistamines for treatment of CSU at the time of in-clinic UAS at screening visit and/or time of the medical record of hives (for at least 3 days prior to the in-clinic UAS or medical record) • Patients must have been on H1-antihistamines for treatment of CSU for at least the 3 consecutive days immediately prior to the first screening visit and must have documented current use on the day of the initial screen…