Researchers working with mice may have found new hope for patients suffering from a rare, untreatable disorder that turns muscle tissue into bone. Fibrodysplasia ossificans progressiva, or “stone man” syndrome, is a genetic disorder that is caused by mutations on a particular gene responsible for bone and muscle growth. This gene is ACVR1 and when functioning correctly, it controls the gradual replacement of cartilage with bone during the course of a child’s development. Patients with mutated ACVR1 experience the gradual replacement of muscle, tendon, ligaments, and other soft tissues with bone throughout their lifetime.

The disease typically begins in the neck and then progresses down the body and into the limbs. Eventually, those afflicted may develop difficulties eating, moving, and breathing as the bone growth continues. There is no cure, no way to slow down the disease, and currently the only treatment is to manage the pain during flare-ups.

There are approximately 800 confirmed cases of Fibrodysplasia ossificans progressive worldwide. The International FOP Association estimates that there are an additional 2,700 unreported cases across the globe.

Researchers have determined that a protein called activin A can cause the mutated gene to become over-active, creating flare-ups. Scientists at Regeneron Pharmaceuticals Inc. were able to take that knowledge, and use it to isolate an anti-body that blocks activin A. Once the antibody was successfully blocked, it stopped bone formation in lab mice with the same genetic mutation. While there are still many steps to go before the treatment can be tested on those afflicted with the disease, the scientific community is praising the discovery.

Director of global research development for the International FOP Association, Betsy Bogard, said it was an “extraordinary” finding:

We are very fortunate and grateful that not only did Regeneron make this basic science discovery, but that, as a biotechnology company with expertise in developing antibodies, they are in a position to act on it and answer the next question about whether this could lead to a meaningful therapy.