Garetosmab Trial Slashed Bone Growth in FOP Patients
A clinical trial found the antibody significantly reduced new bone formation in patients with rare FOP.
Updated on Sept. 28, 2026 in Arthritis
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A clinical trial involving 63 adults with fibrodysplasia ossificans progressiva (FOP) has demonstrated the efficacy of garetosmab in blocking activin A. Patients receiving the Regeneron-made antibody developed far fewer bone lesions over the one-year study compared to those given a placebo.
Why it matters
The study addresses a critical unmet medical need for those suffering from FOP, a rare genetic disorder that affects one in every million people. By curbing abnormal bone growth, the treatment offers potential for preserving long-term mobility and function in patients.
In a study of 63 adults, garetosmab recipients showed a 90% reduction in new bone growth compared to the placebo group. The trial was conducted across 16 countries over a treatment period of just over one year.
The players
Regeneron
This biotechnology company is the manufacturer of the antibody treatment garetosmab.
FOP Friends
This patient advocacy organization is calling on health officials in the UK to approve garetosmab for use within the National Health Service.
Oliver Bedford-Gay
He is an individual diagnosed with FOP who has navigated the condition for over 15 years.
The details
Garetosmab functions as an antibody that inhibits activin A, a protein essential to the abnormal bone growth characteristic of FOP. Researchers suggest the drug may eventually allow for the reconsideration of surgical remobilization efforts for patients with the disorder.
Timeline
Over 15 years ago, Oliver Bedford-Gay received his FOP diagnosis.
Over the past year, trial participants underwent garetosmab treatment.
The Big Picture
This clinical success marks a major milestone in the ongoing clinical development of FOP-targeted protein inhibitors. The trial findings provide definitive evidence that neutralizing activin A can alter the disease progression in a way previously considered impossible.
The approval and potential availability of garetosmab could fundamentally alter the treatment trajectory for the approximately 900 known global FOP cases. Patients and their families should consult with specialists regarding how these findings might impact future clinical care plans.
The takeaway
This breakthrough provides hope for those living with FOP by significantly reducing the development of new bone lesions. The success of the trial underscores the importance of targeting protein pathways in the management of rare genetic musculoskeletal disorders.
Further reading
Find more updates on emerging therapies at Arthritis.
Source note: This article includes information reported by The Independent.
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