To Assess the Efficacy, Safety, and Tolerability of INCB000928 in Participants With Fibrodysplasia Ossificans Progressiva

Inclusion Criteria:

• Female and male participants:

• Cohort 1: ≥ 12 years of age.

• Cohort 2: 6 to < 12 years of age.

• Cohort 3: 2 to < 6 years of age (after eDMC review of interim data from Cohort 2).

• Clinical diagnosis of FOP.

• Willingness to avoid pregnancy or fathering children based on the criteria below.

• Willing and able to undergo low-dose WBCT (excluding the head) imaging withoutrequiring intubation.

• Further inclusion criteria apply.

Exclusion Criteria:

• Pregnant or breast-feeding.

• CAJIS score ≥ 24.

• FOP disease severity that in the investigator's opinion precludes participation.

• Any clinically significant medical condition other than FOP that would, in theinvestigator's judgment, interfere with full participation in the study, pose asignificant risk to the participant, or interfere with interpretation of study data.

• Chronic or current active infectious disease requiring systemic antibiotic,antifungal, or antiviral treatment.

• HIV, HBV, or HCV infection. Note:

• Further exclusion criteria apply.