Rare Bone Disorder Treatment Has Proven Effective
A clinical trial for the rare genetic condition FOP shows that a new antibody therapy significantly reduced new bone growth.
Updated on Sept. 28, 2026 in Arthritis
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A clinical trial of 63 adults has demonstrated that the drug garetosmab can curb abnormal bone growth in people with fibrodysplasia ossificans progressiva (FOP). This rare genetic disorder, which affects approximately one in every million people worldwide, causes muscles and tendons to turn into bone.
Why it matters
The findings address a significant unmet medical need for patients with FOP, as the condition currently lacks broad therapeutic options. Researchers believe this treatment could help preserve long-term mobility and function, potentially opening the door for future surgical interventions.
In a clinical trial involving 63 adults, participants receiving garetosmab over one year developed an average of only one or two new bone lesions compared to 19 in the placebo group. This represents a 90% reduction in new bone growth, though the trial results remain specific to the adult cohort studied.
The players
Regeneron
A biotechnology company that develops and manufactures the antibody therapy garetosmab.
FOP Friends
An advocacy organization representing the interests of patients with the rare genetic disorder FOP.
The details
Garetosmab acts as an antibody that blocks activin A, a protein essential to the abnormal bone growth process seen in FOP. By neutralizing this protein, the drug effectively stops the body's mistaken signal to turn soft tissues into bone. This mechanism is designed to prevent the formation of new lesions that restrict movement and impact physical function.
Timeline
Over 15 years ago, Oliver Bedford-Gay received his FOP diagnosis.
Over the past year, participants received garetosmab treatment.
Health Landscape
This trial marks a major progression in the development pipeline for FOP treatments by providing efficacy data for a condition that affects only 900 people globally. The results represent a shift toward targeted biological therapies for rare genetic diseases that were previously considered untreatable.
While garetosmab has received regulatory approval in the USA, patients in other regions continue to advocate for access. Those affected by FOP should consult with their specialist regarding the current availability of new therapies and how these developments may influence their long-term care.
The takeaway
The study suggests that blocking activin A can drastically reduce the progression of bone growth in FOP patients. Patients and families should discuss the implications of these trial results with a physician to determine how emerging treatment protocols may fit into their ongoing care plans.
Further reading
For more on managing bone-related conditions, visit our Arthritis section.
Source note: This article includes information reported by The Independent.
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