A Study of Diroximel Fumarate (DRF) in Adult Participants From the Asia-Pacific Region With Relapsing Forms of Multiple Sclerosis (RMS)

The primary objectives of this study are to determine the safety and tolerability of DRF administered for up to 24 weeks in adult East Asian participants with RMS (Part 1) and to determine the safety and tolerability of DRF administered for up to 48 weeks in adult East Asian participants with RMS (Part 2).

The secondary objective of this study is to evaluate the pharmacokinetic(s) (PK) of DRF metabolites (monomethyl fumarate \[MMF\] and 2-hydroxyethyl succinimide \[HES\]) following multiple doses of DRF in a subset of adult East Asian participants with RMS (Part 1).


Eligibility Criteria:
Key Inclusion Criteria:

* Must have a diagnosis of RMS, as defined by revised 2017 McDonald's criteria.
* Expanded Disability Status Scale (EDSS) score between 0.0 and 5.0, inclusive, at screening and baseline visit (Day 1).
* Neurologically stable with no evidence of relapse within 30 days prior to baseline visit (Day 1).
* For Japanese participants: Born in Japan and biological parents and grandparents were of Japanese origin. If previously lived outside of Japan for more than 5 years, must not have had a significantly modified diet since leaving Japan.
* For Chinese participants: Born in China, and biological parents and grandparents were of Chinese origin. If previously lived outside of China for more than 5 years, must not have had a significantly modified diet since leaving China.

Key Exclusion Criteria:

* Has a multiple sclerosis (MS) relapse that has occurred within the 30 days prior to randomization and/or the participant has not stabilized from a previous relapse prior to randomization.
* 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.
* History of, or ongoing, malignant disease, including solid tumors and hematologic malignancies.
* 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.
* History of clinically significant recurring or active GI symptoms (e.g., nausea, diarrhea, dyspepsia, constipation) within 90 days of screening, including symptoms that require the initiation of symptomatic medical treatment (e.g., initiation of a medication to treat gastroesophageal reflux disease) or a change in symptomatic medical treatment (e.g., an increase in dose) within 90 days prior to screening.
* History of systemic hypersensitivity reaction to DRF, dimethyl fumarate (DMF), MMF or other fumaric esters, the excipients contained in the formulation, and if appropriate, any diagnostic agents to be administered during the study.
* Evidence of current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection within 14 days prior to Screening, between screening and baseline visit (Day 1), or at baseline visit (Day 1), including but not limited to a fever (temperature \>37.5 degrees Celsius \[°C\]), new and persistent cough, breathlessness, or loss of taste and/or smell. Evidence of current SARS-CoV-2 infection within 14 days prior to Screening or during Screening, will be eligible for rescreening, provided that the participant is asymptomatic for 14 days prior to rescreening.
* Have close contact within 14 days prior to Day 1 with individual(s) with suspected SARS-CoV-2 infection.
* For participants who had close contact with individual(s) with suspected SARS-CoV-2 infection within 14 days prior to Day 1, as determined by the Investigator, will be eligible for rescreening, provided that the participant is asymptomatic for 14 days after the contact.
* History or positive test result at screening for human immunodeficiency virus (HIV).
* Previous participation in this study or previous studies with DRF, DMF, or MMF.
* Has a clinically significant history of suicidal ideation or suicidal behavior occurring in the past 12 months as assessed by the C-SSRS at Screening.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.