Efficacy and Safety of Losmapimod in Treating Participants With Facioscapulohumeral Muscular Dystrophy (FSHD) (REACH)

• Participants must be between 18 and 65 years of age, inclusive.
• Genetically confirmed diagnosis of FSHD 1 or FSHD 2.
• Clinical severity score of 2 to 4 (Ricci Score; Range 0-5), at screening. Participants who are wheelchair-dependent or dependent on walker or wheelchair for activities are not permitted to enroll in the study.
• Screening total RSA (Q1-Q4) without weight in the dominant UE assessed by RWS ≥ 0.2 and ≤ 0.7.
• No contraindications to MRI.

• Previously diagnosed cancer that has not been in complete remission for at least 5 years. Localized carcinomas of the skin and carcinoma in situ of the cervix that have been resected or ablated for cure are not exclusionary.
• Participants who are on drug(s) or supplements that may affect muscle function, as determined by the Investigator: participants must be on a stable dose of that drug(s) or supplement for at least 3 months prior to the first dose of study drug and remain on that stable dose for the duration of the study.
• Orally administered cytochrome P450 (CYP3A4) substrates and multidrug and toxin extrusion (MATE) and organic anion transporter (OAT)3 substrates are not permitted as concomitant therapy during the administration of losmapimod (defined as Baseline visit through end of study treatment).
• Known active opportunistic or life-threatening infections including Human Immunodeficiency virus (HIV) and hepatitis B or C.
• Known active or inactive tuberculosis infection.
• Acute or chronic history of liver disease.
• Known severe renal impairment.
• History of cardiac dysrhythmias requiring anti-arrhythmia treatment(s); or history or evidence of abnormal ECGs.
• Use of another investigational product within 30 days or 5 half-lives (whichever is longer) or currently participating in a study of an investigational device.
• Current or anticipated participation in a natural history study. Previous participation is allowed but participants cannot continue after enrollment in Study 1821-FSH-301.
• Known hypersensitivity to losmapimod or any of its excipients.
• Previous participation in a Fulcrum-sponsored FSHD losmapimod study (FIS-001-2019 or FIS-002-2019).

key are presented.