Up to 102 eligible study subjects will participate in this two cohort study. Cohort A will enroll approximately 58 subjects randomized in a 1:1 ratio (active:placebo). Subjects randomized to the active treatment group in Cohort A will receive CAP-1002A (deramiocel manufactured at Capricor’s manufacturing facility in Los Angeles, CA). Once Cohort A enrollment is completed, Cohort B enrollment will begin. Cohort B will enroll approximately 44 participants randomized in a 1:1 ratio (active:placebo). Subjects randomized to the active treatment group in Cohort B will receive CAP-1002B (deramiocel manufactured at Capricor’s manufacturing facility in San Diego, CA). Both cohorts will include visits at Screening, Baseline/Day 1, Month 1, and Months 3, 6, 9, and 12. Subjects will receive IV infusions of deramiocel or placebo on Day 1 and Months 3, 6, and 9. All subjects will then be eligible to receive additional IV infusions of deramiocel at Month 12, 15, 18, and 21 as part of the open-label phase of the study. All subjects who complete the first open-label extension phase of the study will be eligible to receive additional IV infusions of deramicoel every 3 months in a Long Term Open-Label Extension phase until commercial availability of deramiocel, or until sponsor’s decision to terminate the trial, or the participant withdraws consent.

A primary analysis of efficacy and safety will be performed on the double-blind placebo-controlled phase of the study for both Cohort A and Cohort B combined at Month 12 following 4 administrations of deramiocel or placebo.

The primary efficacy endpoint is the mean change from baseline in upper limb function as assessed by Performance of the Upper Limb test, version 2.0 [PUL 2.0] Total Score at the 12-month time point. Secondary endpoints evaluated at the 12-month time point include assessment of changes in cardiac muscle function and structure by cardiac magnetic resonance imaging [cMRI], changes in hand-to-mouth function [eat 10-bites assessed by the Duchenne Video Assessment (DVA)], quality of life assessments, and biomarker analysis for creatine kinase MB isoenzyme (CK-MB).

Safety evaluations will include adverse events, concomitant medications, physical exam, vital signs, and clinical laboratory testing.

An analysis of extended safety and efficacy will be performed in the subsequent open-label phases of the study.