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

A Phase 3 Global, Randomized, Double-Blind, Placebo-Controlled, 48-Week, Parallel-Group Study of the Efficacy and Safety of Losmapimod in Treating Patients With Facioscapulohumeral Muscular Dystrophy (FSHD) (REACH)

This is a study to evaluate the safety and efficacy of losmapimod in treating participants with Facioscapulohumeral Muscular Dystrophy (FSHD). Participants diagnosed with Facioscapulohumeral muscular dystrophy type 1 (FSHD1) or Facioscapulohumeral muscular dystrophy type 2 (FSHD2) will participate in Part A (Placebo-controlled treatment period) and will be randomized in a 1:1 ratio to receive losmapimod 15 milligrams (mg) or placebo orally twice daily (BID). Upon completion of Part A, participants will have the option to rollover into Part B (open-label extension) to evaluate the long-term safety, tolerability, and efficacy of losmapimod and will receive losmapimod 15 mg orally BID.

Key Inclusion Criteria:

• 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.

Key Exclusion Criteria:

• 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.
• 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).

Note that all other inclusion and exclusion criteria are listed in the protocol and only key are presented.