This study aims to explore how safe and tolerable a drug called SUN-627 is for people aged 18-70 with Non-Active Secondary Progressive Multiple Sclerosis (SPMS) or Primary Progressive Multiple Sclerosis (PPMS). This is a Phase 2a clinical trial, meaning it's in the early stages of testing. Participants won't know if they are getting SUN-627 or a placebo (a harmless pill). The study will look at how the drug moves through and affects the body, and its effects on neuroinflammation (swelling in the brain and spinal cord).

• The study is double-blind, so neither you nor the doctors will know if you're taking the real drug.
• You must not have had an MS relapse in the past 2 years and need to fit certain health criteria to join.
• Participation involves risks, like potential side effects, and you can't join if you're in another study or have certain medical conditions.

Before joining, consider discussing with your doctor to make sure it's the right fit for you and to understand any potential risks.