A Study to Evaluate the Efficacy and Safety of Fenebrutinib Compared With Ocrelizumab in Adult Participants With Primary Progressive Multiple Sclerosis

To join this study, you need to be an adult between 18 and 65 years old (though in Germany and Italy, only those aged 46-65 can join). You must have a confirmed diagnosis of Primary Progressive Multiple Sclerosis (PPMS) based on specific criteria, and your condition should have shown some progression in the year before the study began. Your level of disability, measured by a scale called EDSS, needs to be within a certain range.

You should also be fairly stable in your neurological health for at least a month before starting the study treatments. You'll need to be able to complete some physical tasks, like a timed walk and a hand coordination test, within specific time limits. If you're a woman who could get pregnant, or a man whose partner could get pregnant, you'll need to agree to use effective contraception or avoid sexual activity during the study and not donate eggs or sperm.

It's important to note that if you're taking other medicines for MS symptoms, like fampridine or cannabis, or certain stomach-protecting medicines, you'll need to be on a stable dose before and during the study. The doctors will also check if there are reasons why you *cannot* join the study, but the full list of these reasons isn't provided here.

If you decide to take part in this study, you'll be assigned by chance to one of two groups: one will receive fenebrutinib (a daily tablet), and the other will receive ocrelizumab (given through a drip). Along with your assigned medicine, you will also receive a matching 'dummy' treatment (placebo) to keep the study 'blinded' so neither you nor your study doctor knows which active drug you are receiving. This is a common way to ensure fair results. The study will involve regular visits to the clinic for assessments, health checks, and to receive your medication if it's the drip form. These assessments might include physical exams, questionnaires, and possibly blood tests or scans.

The initial part of the study is called the 'Double-Blind Treatment' (DBT) phase. The duration of this phase isn't specified, but it involves continued treatment and close monitoring. After this phase, there might be an 'Open-Label Extension' (OLE) phase. This means if the initial results are positive, you could continue to receive fenebrutinib, and in this phase, both you and your doctor would know you are receiving the active drug. Throughout the study, it's expected that you won't be using other MS disease-modifying treatments. If you stop the study early for any reason, you won't be replaced by another participant. The total length of your participation would depend on whether you join the optional open-label extension.