RecruitingPhase 2Biological interventionA Study to Assess the Tolerability of Ianalumab (VAY736) With Investigator's Choice Thrombopoietin Receptor Agonist (IC TPO-RA) in Patients With Primary Immune Thrombocytopenia (ITP)The purpose of this study is to investigate the tolerability of ianalumab (9 mg/kg) with investigator's choice thrombopoietin receptor agonist (IC TPO-RA) in participants diagnosed with primary immune thrombocytopenia (ITP) who have been treated with at least one but no more than four prior treatments, and with no change in IC TPO-RA dose in at least the last 14 days prior to the start of ianalumab.