Double Blind Combination of Rituximab by Intravenous and Intrathecal Injection Versus Placebo in Patients With Low-Inflammatory Secondary Progressive Multiple Sclerosis (RIVITaLISe)

Background: \- Secondary-progressive multiple sclerosis (SP-MS) is the chronic phase of multiple sclerosis (MS). The majority of people who have relapsing-remitting MS eventually develop SP-MS. There are currently no effective treatments for SP-MS. Researchers are interested in determining whether the drug rituximab, which is used to treat rheumatoid arthritis and some types of cancer, is able to target certain white blood cells that are thought to play a role in the progression of SP-MS. To ensure that the rituximab will reach the brain and spinal cord, participants will receive it by intravenous drip and by intrathecal injection (through a lumbar puncture into the cerebrospinal fluid). Objectives: \- To evaluate the safety and effectiveness of combined intravenous and intrathecal rituximab in individuals with secondary-progressive multiple sclerosis. Eligibility: \- Individuals between 18 and 65 years of age who have been diagnosed with SP-MS and have been off any form of immunosuppressive therapy for at least 3 months. Design: \- The study will involve a 1-year pretreatment baseline series of visits, followed by a 2-year treatment period. Participants will provide blood samples throughout treatment as directed by the study researchers, and additional studies may be performed during the study period if participants consent to further investigation.