A Phase 1/2a Study of Oral PRO-1562 in Healthy Subjects and Patients With Relapsing Multiple Sclerosis

Phase 1 Inclusion Criteria: 1. Able and willing to provide written informed consent 2. Body weight ≥ 48 kg (105.6 lbs) and body mass index (BMI) ≥ 18.5 and ≤ 30 kg/m2 3. Must be in good health and without clinically significant abnormalities by review of medical and surgical history, physical examination, vital signs measurement, and 12-lead ECG 4. No clinically-significant laboratory abnormalities 5. Willing and able to use highly-effective forms of contraception for at least 30 days after the end of study visit. Phase 1 Exclusion Criteria: 1. Ongoing medical condition requiring systemic therapy. 2. Ongoing infection 3. mRNA or live vaccine during the past 60 days 4. History of significant hypersensitivity, intolerance, or allergy to any drug/medication 5. Participation in another clinical trial with an investigational agent within 30 days prior to Check-in or 5 half-lives (if known) of the investigational drug's PK, PD, or biological activity (if known), whichever is longer 6. Positive alcohol breath test or urine screen for drugs of abuse. 7. Use or intent to use natural products or nutritional/dietary supplements (including St. John's wort), vitamins, minerals, and phytotherapeutic /herbal/plant-derived preparations within or received within 14 days or 5 half-lives prior to Check-in, whichever is longer. 8. Poor peripheral venous access. 9. Receipt of blood products within 2 months prior to Check-in. 10. Donation of blood or blood products during the 4 weeks prior to Check-in. 11. Participants who in the opinion of the Principal Investigator (or designee), should not participate in this study