A Phase 2a Study of SUN-627 in Participants With Non-Active Secondary Progressive and Primary Progressive Multiple Sclerosis (SPMS/PPMS)

Inclusion Criteria: 1. Aged 18-70, inclusive 2. Diagnosis of PPMS or non-active SPMS 3. No MS relapses in the past 2 years 4. Evidence that MS has continued to get worse over time 5. A level of disability that fits the study requirements Exclusion Criteria: 1. Use of certain medications or treatments before the study, or need for these treatments during the study 2. Current participation in another research study 3. Certain abnormal heart rhythm findings on ECG or other heart conditions that may increase risk 4. Certain serious or unstable medical conditions that could make the study unsafe 5. Active infection, recent infection, or a history of repeated infections Additional inclusion and exclusion criteria are outlined in the full study protocol.