FDA Approves First Drug to Slow Rare Bone Disease FOP

After decades of research, the FDA has approved the first treatment for a devastating condition that slowly locks people's bodies in place by turning soft tissue into bone.

Pasatru is now available for adults with fibrodysplasia ossificans progressiva, or FOP, an ultra-rare genetic disorder that causes muscles, tendons and ligaments to transform into bone. The new drug reduced abnormal bone formation by more than 90% in clinical trials.

FOP affects roughly 900 people globally, turning everyday movements into a battle. Speaking, eating, walking and breathing become increasingly difficult as rogue bone grows in the jaw, spine, hips and rib cage. Most patients need wheelchairs by age 30, with a median life expectancy of 56 years.

The drug works by blocking Activin A, a protein scientists at Regeneron discovered drives the abnormal bone growth. In the 56-week OPTIMA trial, patients receiving the treatment developed just 1 to 2 new bone lesions compared to 19 in the placebo group.

"For people living with FOP, every irregular new bone formation is a step toward disability and potential loss of mobility," said Dr. Kathryn Dahir, who led parts of the trial at Vanderbilt University. "We now have a new treatment that can positively affect patients."

The treatment also dramatically reduced disease flare-ups. Patients on the higher dose experienced 88% fewer clinician-assessed flare-ups than those on placebo. These flare-ups signal new bone is forming and often mean another part of the body will lose function.

Recognizing that many FOP patients struggle with mobility, doctors can administer Pasatru through home infusion where appropriate. Patients receive monthly infusions, with dosing adjusted based on individual tolerance.

Why This Inspires

This approval represents more than just a new drug. It's the result of researchers refusing to give up on a tiny patient population that pharmaceutical companies often overlook. When diseases are this rare, developing treatments rarely makes financial sense, yet Regeneron invested decades into understanding FOP's underlying biology.

The FOP community has waited a lifetime for options. "This approval is monumental for our community, providing a vital new therapy that can have a significant impact on the life of someone with FOP," said Michelle Davis, Executive Director of the International FOP Association.

For families watching loved ones gradually lose mobility, knowing that science hasn't forgotten them matters just as much as the medicine itself.

The drug is under review in Europe and additional regulatory submissions are planned worldwide, including in Japan, potentially bringing relief to FOP patients across the globe.