REGN2477 (garetosmab)

REGN2477 (garetosmab)

FOP is caused by a mutation in a gene called “ACVR1” which encodes for the receptor protein “ACVR1/ALK2.” In healthy individuals, a protein called Activin A usually turns this receptor “off.” However, in FOP, Activin A turns the mutant receptor “on,” resulting in the abnormal bone growth (heterotopic ossification or HO) that is characteristic of FOP. REGN2477 (also known as garetosmab) is an antibody that binds (i,e. holds onto) to Activin A, and blocks its activity. By binding and blocking Activin A, REN2477 may prevent the formation and stop the growth of HO in FOP. REGN2477 has received Orphan Drug status for FOP from the U.S. Food and Drug Administration (FDA), and orphan status for the treatment of FOP in the EU.

About the Clinical Trial

The REGN2477

Phase 3
Phase 3: Studies that further test safety and begin to test the effectiveness of the drug, often at a variety of doses.

trial is a global, multi-center, placebo-controlled trial. Approximately 66 adults 18 years of age or older with the classic FOP mutation (R206H) or non-classic mutations will be enrolled. The trial is designed to evaluate the safety of REGN2477, and whether monthly dosing will reduce the formation of new HO and reduce the signs and symptoms of flare-ups. 

Eligibility Criteria Icon
Eligibility Criteria*
  • AGE: ≥ 18
  • DISEASE ACTIVITY: Participants need to have had FOP disease activity within one year of the screening visit.
  • MUTATIONS: R206H and other mutations of the ACVR1 gene resulting in heterotopic ossification
Study Design Icon
Study Design*
  • STUDY TYPE:  Interventional
  • PLACEBO-CONTROLLED:  Yes, participants will be randomized to high-dose garetosmab, low-dose garetosmab, or
    Placebo (control): An inactive product that resembles the test medicine or procedure, but without a treatment value. A placebo can be a pill, a powder, or a solution that resembles the test drug, but has no physical effect.  
Status Icon

Phase 3,
Phase 3: Studies that further test safety and begin to test the effectiveness of the drug, often at a variety of doses.  
Open, Enrolling

Therapy Approach Icon
Therapy Approach

Blocking Antibody

Study Sponsor Icon
Study Sponsor

Regeneron Pharmaceuticals

*For the complete list of eligibility criteria and details on this study, visit and enter Identifier NCT05394116.

Participating Clinical Sites (as of March 28, 2023)

Lariboisière Hospital AP-HP
Principal Investigator: Thomas Funck-Brentano, MD, PhD

Nagoya University Hospital
Principal Investigator: Kenichi Mishima, MD

Kuala Lumpur Hospital
Principal Investigator: Kavitha Rethnavelu

Medyk Medical Center Hospital 
Principal Investigator: Jacek Tabarkiewicz, MD, PhD

Ramon y Cajal University Hospital
Principal Investigator: Javier Bachiller Corral, MD

Royal National Orthopaedic Hospital NHS Trust
United Kingdom
Principal Investigator: Richard Keen, MD
Alternate Contact: Jackie Vinton


The IFOPA does not endorse nor recommend specific clinical trials. Please speak with your doctor if you are interested in participating in a clinical trial.

Make a Difference

Donate Connect Fundraise
Already a Member? Sign In

Sign Up for FOP Connection, Our Monthly eNewsletter