This clinical trial is focused on studying the long-term safety and tolerability of a medication called Tolebrutinib in individuals with different types of Multiple Sclerosis (MS). Multiple Sclerosis is a disease that affects the nervous system, and this study includes participants with relapsing MS, primary progressive MS, and non-relapsing secondary progressive MS. The medication being tested, Tolebrutinib, is taken in the form of film-coated tablets. The study also involves the use of a placebo, which is a substance with no active medication, to compare the effects of Tolebrutinib.

The purpose of this study is to determine how safe and tolerable Tolebrutinib is over a long period. Participants will take the medication orally, and the study will last for up to 36 months. During this time, researchers will monitor participants for any adverse events, which are unwanted effects that may occur during the study. The study will also look at how the medication affects the progression of disability in participants with MS and track any changes in the brain using Magnetic Resonance Imaging (MRI), a type of scan that provides detailed images of the brain.

In addition to Tolebrutinib, the study involves other substances like Anhydrous Cholestyramine, which is used to bind certain substances in the intestines, and Magnetic Resonance Imaging Contrast Media, which helps improve the clarity of MRI images. These substances are used to support the study’s objectives and ensure accurate monitoring of the participants’ health. The study aims to provide valuable information on the long-term use of Tolebrutinib in managing Multiple Sclerosis.