A Study to Investigate the Safety, Pharmacokinetics (PK), and Efficacy of Garetosmab in Children and Adolescents With Fibrodysplasia Ossificans Progressiva (FOP)

NCT07559513 | Not Yet Recruiting Phase 3 DMC FDA Drug

• 2 other identifiers: R2477-FOP-24132024-518415-19-01
• Study Type: interventional
• Target: 18
• Locations: 0 countries
• Sites: N/A

Brief Summary

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:

• What side effects may happen from taking the study drug
• How much study drug is in the blood at different times
• Whether the body makes antibodies against the study drug (which could make the study drug less effective or could lead to side effects)

Conditions

Fibrodysplasia Ossificans Progressiva (FOP)

Keywords

Type I Activin A Receptor (ACVR1) FOP-causing mutation

Outcome Measures

Primary Outcomes (5)

• Occurrence of Treatment-Emergent Adverse Event (TEAEs)

  Baseline to week 28

• Occurrence of TEAEs

  Baseline to week 56

• Severity of TEAEs

  Baseline to week 28

• Severity of TEAEs

  Baseline to week 56

• Concentrations of functional garetosmab in serum

  Through week 56

Secondary Outcomes (16)

• Total volume of new Heterotopic Ossification (HO) lesion

  At week 28 and week 56

• Number of new HO lesions

  At week 28 and week 56

• Occurrence of new HO lesions

  At week 28 and week 56

• Number of clinician-assessed flare-ups

  Through week 28 and week 56

• Occurrence of clinician-assessed flare-ups

  Through week 28 and week 56

Study Arms (3)

Cohort 1: Adolescents

EXPERIMENTAL

Drug: garetosmab

Cohort 2: Children

EXPERIMENTAL

Drug: garetosmab

Cohort 3: Children and Adolescents

EXPERIMENTAL

Drug: garetosmab

Interventions

garetosmab DRUG

Administered per the protocol

Also known as: REGN2477

Cohort 1: Adolescents; Cohort 2: Children; Cohort 3: Children and Adolescents

Eligibility Criteria

• Age: 2 Years - 18 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64)

You may qualify if:

• For USA participants, age criteria are 4 to \< 18 years old, at the time of the administration of the first dose of study intervention. Non-USA participants age criteria are 2 to \< 18 years old
• Must have a confirmation of FOP diagnosis, as described in the protocol
• At the time of enrollment, participants must weight:
• Cohort 1 \> 30 kg
• Cohort 2 \> 30 kg
• Cohort 3 ≤ 30 kg

You may not qualify if:

• Cumulative Analog Joint Involvement Scale (CAJIS) score \> 19 at the time of screening
• Participant has significant concomitant illness or history of significant illness, as described in the protocol
• Previous history or diagnosis of cancer
• Ongoing significant viral or bacterial illness, within 2 weeks of the first study drug administration
• History of severe respiratory compromise requiring oxygen, respiratory support
• Known history of cerebral vascular malformation
• Participants with a history of severe, non-traumatic bleeding requiring transfusion or hospitalization for hemodynamic compromise
• Participants with a known pre-existing medical history of a bleeding diathesis, as described in the protocol

Sponsors & Collaborators

• Regeneron Pharmaceuticals: lead

MeSH Terms

Conditions

Myositis Ossificans

Condition Hierarchy (Ancestors)

Myositis; Muscular Diseases; Musculoskeletal Diseases

Study Officials

• Clinical Trial Management

  Regeneron Pharmaceuticals

  STUDY DIRECTOR

Central Study Contacts

Clinical Trials Administrator

CONTACT

844-734-6643; clinicaltrials@regeneron.com

Study Design

• Study Type: interventional
• Phase: phase 3
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: April 22, 2026
• First Posted: April 30, 2026
• Study Start (Estimated): July 30, 2026
• Primary Completion (Estimated): December 10, 2028
• Study Completion (Estimated): December 21, 2029
• Last Updated: April 30, 2026

Record last verified: 2026-03

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ICF, CSR, ANALYTIC CODE
• Time Frame: When Regeneron has: * received marketing authorization from major health authorities (e.g., FDA, European Medicines Agency (EMA), Pharmaceuticals and Medical Devices Agency (PMDA), etc.) for the product and indication or has globally discontinued development of the product for all indications on or after April 2020 and has no plans for future development * made the study results publicly available (e.g., scientific publication, scientific conference, clinical trial registry) * the legal authority to share the data, and * ensured the ability to protect participant privacy
• Access Criteria: Qualified researchers can submit a proposal for access to individual patient or aggregate level data from a Regeneron-sponsored clinical trial through Vivli. Regeneron's Independent Research Request Evaluation Criteria can be found at: https://www.regeneron.com/sites/default/files/Regeneron-External-Data-Sharing-Policy-and-Independent-Research-Request-Evaluation-Criteria.pdf