Fibrodysplasia Ossificans Progressiva (FOP) is a rare, severely disabling disease characterized by the presence of bone in soft tissue where bone normally does not exist, known as Heterotopic Ossification (HO). It is often associated with painful, recurrent episodes of soft tissue swelling (flare-ups) that lead to abnormal stiffening and immobility (ankyloses) of major joints with cumulative and irreversible loss of movement and disability. This study will evaluate the efficacy of 2 dosing regimens of IPN60130 in inhibiting new HO volume compared with placebo (a dummy treatment) in adult and paediatric participants with FOP. It will be assessed by a scan (provides internal images of the body) called low dose Whole Body Computed Tomography (WBCT), excluding head. Adults and participants 15 years of age or older are also eligible for a sub study to evaluate HO lesions assessed by another type of scan, Fluorine-18-labelled natrium fluoride Positron Emission Tomography-Computed Tomography ([18F]NaF PETCT ). This will be a 3-part study: Part A will be a 12-month, 3-arm, parallel-group, randomised, double-blind, placebo-controlled period during which participants will be randomised to low or high weight-based IPN60130 dosage arms or placebo, Part B will be a 12-month, 2-arm, randomised, double-blind period during which participants will receive high or low weight-based daily dosages of IPN60130. Participants completing Part A will enter Part B: placebo recipients from Part A will be randomised to one of the IPN60130 dosage arms with a 1:1 ratio, whereas participants receiving IPN60130 will remain in their respective dosage arms. Part C will be a 36-month, extension period. All participants completing Part B will continue in the same IPN60130 treatment arm for additional 36-month treatment in Part C.