FDA approves Pasatru, the second treatment for rare bone disorder

The FDA has approved Regeneron’s Pasatru (garetosmab-grts) to reduce the formation of new heterotopic ossification (HO) lesions and flare-ups in adults with fibrodysplasia ossificans progressiva (FOP).

FOP is an ultra-rare genetic disease that transforms the body’s soft tissue into bone. It affects about 900 people worldwide, and most patients will require a wheelchair by the age of 30. Life expectancy is about 56 years of age.

Pasatru is a human monoclonal antibody that blocks Activin A, a protein that is critical in the development of heterotopic ossification lesions in people with FOP. In studies of mice, inhibition of Activin A prevents HO.

Pasatru is available in two doses and given intravenously every four weeks. It will be available within a few days and have an annual list price of $1.4 million based on dosing a patient of the average weight in the trial at 10 mg/kg dosing, according to a Regeneron spokesperson. Given the 3 mg/kg dosing option and varying patient weights, the company expects an annual list pricing range at launch of $693,000 to $2.1 million.

Regeneron offers patient support programs that offer resources for patients and healthcare providers, including product information, insurance benefit verification, and information about potential financial support.

“Regeneron recognizes that the financial cost of medicines like Pasatru is top-of-mind for patients and physicians in determining treatment decisions,” the spokesperson said. “When determining the U.S. list price of Pasatru, Regeneron considered the significance of this milestone for the community, alongside the decades of scientific research, development and investment that went into bringing this innovative medicine to adults impacted by FOP.”

The approval was based on efficacy and safety data from the phase 3 OPTIMA trial evaluating Pasatru in 63 adults with FOP. At 56 weeks, both doses of Pasatru reduced the total number of new HO lesions compared with placebo. Additionally, the number of clinician-assessed flare-ups, a key secondary endpoint, was also reduced. But changes in the proportion of patients with patient-reported flare-ups through week 56 were not significantly different between placebo and Pasatru treatment groups.

“For people living with FOP, every irregular new bone formation is a step toward disability and potential loss of mobility,” Kathryn Dahir, M.D., professor in the Department of Internal Medicine, division of Endocrinology, Diabetes, and Metabolism at Vanderbilt University, and a primary investigator for the OPTIMA trial, said in a news release. “With the ability to reduce the number of new bone lesions and flare-ups, we now have a new treatment that can positively affect patients.”

Pasatru has a warning about fetal harm when administered during pregnancy, as well as warnings about skin and soft-tissue infections that may require hospitalization.

During the trials, serious treatment-emergent adverse events occurred in two patients treated with 10 mg/kg Pasatru, one patient treated with 3 mg/kg Pasatru, and two patients treated with placebo. The most common adverse reactions in patients treated with Pasatru were abscess, acne, increased hair growth, madarosis (loss of eyebrows), oral ulcers, epistaxis (nosebleeds), folliculitis, paronychia (nail infection), and rash.

Pasatru is the second treatment approved by the FDA for FOP. Ipsen’s Sohonos (palovarotene) was approved in August 2023 to reduce new abnormal bone formation in people living with FOP. Sohonos is indicated to treat girls 8 years of age and older and boys 10 years of age or older. When Sohonos launched, it had a price of $624,000 based on a 5 mg dose per day.