Key Inclusion Criteria:  Have a body mass index (BMI) between 18 and 30 kilograms per meter square (kg/m^2), inclusive. Negative polymerase chain reaction (PCR) test result for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at screening and Day -1. For Chinese participants: was born in China, and biological parents and grandparents were of Chinese origin. If living outside China for more than 5 years, must not have had a significantly modified diet since leaving China.  Key Exclusion Criteria:  History of severe allergic or anaphylactic reactions or of any allergic reactions that, in the opinion of the investigator, are likely to be exacerbated by any component of the study treatment; or systemic hypersensitivity reactions to DRF, dimethyl fumarate (DMF), MMF, other fumaric esters, excipients in the formulation, or diagnostic agents to be administered during the study. Confirmed demonstration of corrected QT interval, using Fridericia's correction method, of >450 milliseconds (ms) for males and >460 ms for females. Has a history of gastrointestinal (GI) surgery (except appendectomy or cholecystectomy that occurred more than 6 months prior to screening), irritable bowel syndrome, inflammatory bowel disease (Crohn's disease, ulcerative colitis), or other clinically significant and active GI condition, per the investigator's discretion. Has experienced clinically significant acute GI symptoms in the judgment of the investigator within 30 days prior to admission. History or positive test result at screening for human immunodeficiency virus (HIV). Chronic, recurrent, or serious infection, as determined by the investigator, within 90 days prior to screening and between screening and Day -1. Current enrollment in any other drug, biological, device, or clinical study or treatment with an investigational drug or approved therapy for investigational use within 30 days prior to Day -1, or 5 half-lives, whichever is longer. Previous participation in this study or previous studies with DRF or DMF.  NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.