After more than 10 years in development, Regeneron secured a landmark approval for its monoclonal antibody garetosmab, now commercially known as Pasatru. The drug has become the second cleared by the FDA to treat fibrodysplasia ossificans progressiva (FOP) and the first to reduce clinician-assessed flare-ups in adults with the disease.
Pasatru, given intravenously every four weeks, is designed to block what is believed to be the key protein behind the FOP disease process—activin A—which was pinpointed by Regeneron scientists as a possible target for treating FOP more than a decade ago.
The approval follows a victory last year in a phase 3 study, which randomized 63 adults with FOP to receive one of two doses of the anti-activin A antibody or placebo every four weeks for 56 weeks. In the trial, both high- and low-dose Pasatru reduced new bone lesions in FOP patients by 90% over 56 weeks. And high dose Pasatru reduced bouts of painful localized inflammation by 89% compared to placebo, too.
By the end of the trial, an independent data monitoring committee recommended all patients on placebo be switched to Pasatru as soon as possible.
FOP is an ultrarare genetic disorder—there are roughly 900 cases worldwide—wherein the body’s soft tissues progressively turn to bone. It’s marked by painful flare-ups: hot and swollen masses in the tissue that precede the permanent conversion of muscle, tendons and ligaments to bone. Over time, the ossification restricts patient movement, and the pain becomes chronic as the increasing bone mass compresses nerves and fuses joints.
