Orelabrutinib is a CNS-penetrable BTK inhibitor. This is a phase 3, randomized, double-blind, parallel-group, multicenter study to evaluate the efficacy and safety of orelabrutinib compared with placebo in patients with PPMS. Patients will be treated for approximately 30 to 60 months, with a minimum treatment duration of 12 months. The study will enroll approximately 705 subjects in a 2:1 randomization (orelabrutinib: placebo), globally.

Inclusion Criteria:

• 18 to 60 years of age, inclusive
• Diagnosed with Primary Progressive MS (PPMS) according to 2017 McDonald criteria
• Participant must have documented evidence of disability progression observed during the 24 months before screening.
• Expanded disability status scale (EDSS) score between 3.0 to 6.5 points, inclusive, at Screening.

Exclusion Criteria:

• Diagnosed with relapsing-remitting MS (RRMS) or secondary progressive MS (SPMS)
• Immunologic disorder other than MS or any other conditions requiring oral, intravenous (IV), intramuscular, or intra-articular corticosteroid therapy.
• History or current diagnosis of other neurological disorders that may mimic MS
• History of any other significant active medical condition
• History of suicidal behavior within 6 months prior to Screening
• Any prior history of malignancy if no recurrence within 5 years
• Patients on anticoagulation, or antiplatelet therapy will be excluded
• Patients took strong/moderate CYP3A inhibitors or strong/moderate CYP3A inducerswithin 14 days
• Clinically significant laboratory abnormalities at Screening.
• Any allergy, contraindication, or inability to tolerate orelabrutinib or any of the excipients in the study intervention
• Vaccination with live or live-attenuated virus vaccine within 1 month prior to Screening
• History of alcohol abuse or alcohol use disorder or other drug abuse within 12 months prior to screening.