A medicine from Regeneron Pharmaceuticals for an ultra-rare disease that causes bone to grow where it shouldn’t won approval on Wednesday, the capstone of a three decade-long effort.

The hope is that the new medicine, called Pasatru, can help patients with fibrodysplasia ossificans progressiva, or FOP, maintain their mobility and perhaps even live longer. Typically, people with FOP rely on wheelchairs by age 25 as the bone accumulation locks up their limbs, and only some live into their 50s.

“Having an effective treatment, you’re hoping that you’ll change that trajectory,” said Richard Keen of London’s Royal National Orthopaedic Hospital, who was the primary investigator in the medicine’s pivotal trial. “You’re almost completely stopping the new [bone] forming, and therefore their condition will not deteriorate.”