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

Inclusion Criteria: * Adult patients, age 18 to 65 years (inclusive). * EDSS score at screening between 3.0 to 6.5 (both inclusive) * No evidence of relapse in the last 24 months before randomization, AND Patients diagnosed according to 2017 revised McDonald Criteria 1 and the 2013 revised classification of disease courses 2 as either 1. SPMS inpatients showing evidence of Gd+MRI lesions (active SPMS) or without Gd+MRI lesions (non-active SPMS) in the last 12 months, OR 2. PPMS * Willingness and ability to comply with the protocol. * Written informed consent given by the patient before the beginning of any study-related procedure. * Documented evidence of disability progression not temporarily related to a relapse in the last 24 months before randomization, adjudicated by a central independent reviewer Exclusion Criteria: * Any disease other than MS that may better explain the signs and symptoms, including a history of complete transverse myelitis. * Clinical signs or presence of laboratory findings suggestive for neuromyelitis optica (NMO) spectrum disorders or myelin oligodendrocyte glycoprotein (MOG)-associated encephalomyelitis (i.e.,presence of anti-NMO \[aquaporin-4\] antibodies or anti-MOG antibodies). * Previous or current use of MS treatments lifelong, or within a pre-specified time period. * Use of any investigational product within 8 weeks or 5 the respective PK half- life before the date of informed consent, whichever is longer, and throughout the study.For some investigational products, prolonged biological effects beyond 8 weeks should be considered. * Positive test for severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2) within14 days before randomization. In case of known SARS-CoV-2 infection, patients should be randomized no earlier than 14 days after 2 consecutive negative tests confirming virus negative status.The screening period can be extended for these patients to accommodate the required virus negativity. * Positive IFN-gamma release assay (IGRA) for Mycobacterium tuberculosis at SV1. * Positive hepatitis B virus (HBV) surface antigen, hepatitis B core antibody, positive hepatitis C virus (HCV) antibody, and/or HIV-antigen-antibody test at SV1.