A Phase 3 interventional study of garetosmab in Fibrodysplasia Ossificans Progressiva (FOP), sponsored by Regeneron Pharmaceuticals. Not yet recruiting. Open to participants aged 2 Years to 18 Years. Per ClinicalTrials.gov, last updated 2026-08-24.
Sponsored by Regeneron Pharmaceuticals · Phase 3, Interventional, and Treatment
This study is researching an experimental drug called garetosmab, referred to as "study drug". The study is focused on children and adolescent participants with FOP.
The aim of the study is to see how safe, tolerable, and effective the study drug is.
The study is looking at several other research questions, including:
25 studies on the registry are indexed under Myositis Ossificans; 5 are open to participants now.
This study's planned enrollment of 18 is below the median of 48 across 15 interventional studies indexed under Myositis Ossificans.
Browse Myositis Ossificans studies →Regeneron Pharmaceuticals is the lead sponsor of 400 studies on the registry; 91 are open to participants now.
Of its 120 completed or terminated interventional studies of FDA-regulated products, 77 (64%) have results posted.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria:
At the time of enrollment, participants must weight:
Key Exclusion Criteria:
NOTE: Other Protocol-defined Inclusion/Exclusion Criteria Apply
Drug: garetosmab
Drug: garetosmab
Drug: garetosmab
Administered per the protocol
Also known as: REGN2477
Occurrence of Treatment-Emergent Adverse Event (TEAEs)
Time frame: Baseline to week 28
Occurrence of TEAEs
Time frame: Baseline to week 56
Severity of TEAEs
Time frame: Baseline to week 28
Severity of TEAEs
Time frame: Baseline to week 56
Concentrations of functional garetosmab in serum
Time frame: Through week 56
Total volume of new Heterotopic Ossification (HO) lesion
Time frame: At week 28 and week 56
Number of new HO lesions
Time frame: At week 28 and week 56
Occurrence of new HO lesions
Time frame: At week 28 and week 56
Number of clinician-assessed flare-ups
Time frame: Through week 28 and week 56
Occurrence of clinician-assessed flare-ups
Time frame: Through week 28 and week 56
Number of patient/caregiver-reported flare-ups
Time frame: Through Week 28 and week 56
Occurrence of patient/caregiver-reported flare-ups
Time frame: Through week 28 and week 56
Change from baseline in Tanner puberty scale
Tanner puberty scale or stages: Staging of sexual development is graded on a 5-point ordinal scale ranging from 1 (prepubertal) to 5 (adultlike) for female breast development, male external genitals, and pubic hair
Time frame: At week 28 and week 56
Characteristics of menstrual cycles for female participants who reached menarche
Time frame: Over 28 weeks and 56 weeks
Height-for-age Z-Scores according to the World Health Organization (WHO) Growth Reference Data for Children
Participants 5-19 years of age Z-score represents standardized measure of how far an individual deviated from study cohort average at baseline. A higher Z-score reflects better performance.
Time frame: Through week 56
Concentrations of total activin A in serum
Time frame: Through week 56
Occurence of Anti-Drug Antibody (ADA) to garetosmab
Time frame: Through week 56
Magnitude of ADA to garetosmab
Time frame: Through week 56
Change from baseline in hearing function as assessed by audiometry
Time frame: At week 28 and week 56
Change from baseline in Pediatric Quality of Life inventory (PedsQL) scores
Age-appropriate PedsQL Generic Core Scales will be used to measure HRQoL in children and adolescents. Response options include 5-point Likert scale (or 3-point Likert scale for the young children self-report) for each item asking about experience within the past week. Global scores are transformed to a 0 to 100 scale with higher scores indicating better quality of life.
Time frame: At week 28 and week 56
Acceptability and tolerability assessment via exit interview
Each interview will be conducted by trained external interviewers following a semi-structured interview guide of questions for the participants about their overall experience in the trial.
Time frame: Up to week 30
No study locations are listed for this record.
Plan to share: Yes — All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing.
Supporting information: Study protocol, Sap, Icf, Csr, Analytic code
No publications or documents are linked to this record.
This study is not yet recruiting, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.
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Regeneron Pharmaceuticals