Study to Evaluate the Efficacy, Safety and Tolerability of IMU-838 in Patients With Relapsing Multiple Sclerosis

Inclusion Criteria: * Male or female patient (age ≥18 to ≤55 years). * Patients with an established diagnosis of MS according to 2017 McDonald Criteria. * Patients with RMS comprising of relapsing remitting MS (RRMS) and active secondary progressive MS, both defined according to Lublin criteria 1996 and 2014. * Active disease as defined by Lublin 2014 evidenced prior to Screening by: 1. At least 2 relapses in the last 24 months before randomization, or 2. At least 1 relapse in the last 12 months before randomization, or 3. A positive Gd+ MRI scan (brain and/or spine) in the last 12 months prior to randomization. * Willingness and ability to comply with the protocol. * Written informed consent given prior to any study-related procedure. Exclusion Criteria: * Patients with non-active secondary progressive MS and primary progressive MS. * Any disease other than MS that may better explain the signs and symptoms, including history of complete transverse myelitis. * Clinical signs or presence of laboratory findings suggestive for neuromyelitis optica (NMO) spectrum disorders or myelin oligodendrocyte glycoprotein (MOG)-IgG-associated encephalomyelitis * Any active and uncontrolled coexisting autoimmune disease, other than MS (except for type 1 diabetes mellitus and inflammatory bowel disease) * Use of experimental/investigational drug (with the exception of COVID-19 vaccines approved by emergency use authorization) and/or participation in drug clinical studies within 6 months prior to Screening * Previous or current use of MS treatments lifelong, or within a pre-specified time period. * Use of the pre-specified concomitant medications. * Clinically significantly abnormal and pre-specified lab values. * History of chronic systemic infections within 6 months before the date of informed consent. * Diagnosis or suspected liver function impairment, which may cause fluctuating liver function tests during this study. * Known history of nephrolithiasis or underlying condition with a strong association of nephrolithiasis. * History or clinical diagnosis of gout. * History or presence of any major medical or psychiatric illness * Substantial medical condition that could create undue risk to the patient, could affect adherence with the study protocol or could undesirably affect study outcomes