Fibrodysplasia Ossificans Progressiva (FOP) is a rare, severely disabling disease characterized by heterotopic ossification (HO), i.e., abnormal bone formation, often associated with painful, recurrent episodes of soft tissue swelling (flare-ups). Lesions begin in early childhood and lead to progressive ankyloses of major joints with resultant loss of movement. In this study, the ability of different palovarotene dosing regimens to prevent the formation of new HO will be evaluated in adult and pediatric participants with FOP.