Regeneron has won US Food and Drug Administration (FDA) approval for Pasatru (garetosmab-grts) in a rare connective tissue disorder, placing it in direct competition with Ipsen’s Sohonos (palovarotene).
Pasatru is approved to reduce new heterotopic ossification and reduce clinician-assessed disease flare-ups in adults with fibrodysplasia ossificans progressiva (FOP). The monoclonal antibody (mAb), which is administered intravenously once monthly, works by blocking Activin A – a protein critical in the development of lesions in FOP patients. The recommended starting dosage of Pasatru is 10 mg/kg, which can then be decreased to 3 mg/kg.
The FDA’s authorisation was based on the successful Phase III OPTIMA trial that enrolled 63 patients with the ultra-rare disease. At 56 weeks, Pasatru led to a significant reduction in the number of new heterotopic ossification lesions compared to placebo – up to 90% at the higher dose. The drug also cut the number of flare-ups at two dose levels.
FOP is an ultra-rare genetic disorder in which muscles, tendons, ligaments and other connective tissues are progressively infiltrated by rogue bone formation, a process known as heterotopic ossification. When this happens in the jaw, spine, or rib cage, basic daily activities can become limited. In theory, this creates a second skeleton, which is why the condition is also known as “stone man disease”. Worldwide, approximately 900 people are diagnosed with FOP, and most patients are wheelchair-bound by age 30, with the median age of survival being 56.
The approval means Pasatru is in direct competition with Ipsen’s Sohonos, which was until now the only therapy approved for FOP. Ipsen’s product, a tablet taken daily, gained FDA approval in 2023 but struggled with patient uptake due to its high list price of $624,000. Regeneron has not disclosed how much it will charge for Pasatru.
Dr Kathryn Dahir, professor at Vanderbilt University’s endocrinology, diabetes and metabolism department and a primary investigator for the OPTIMA trial, said: “For people living with FOP, every irregular new bone formation is a step toward disability and potential loss of mobility. 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.”
Michelle Davis, executive director of the International FOP Association, commented: “FOP is a relentless, restrictive condition that severely impacts the lives of those diagnosed and their families. 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."
A regulatory submission for Pasatru is also currently under review by the European Medicines Agency (EMA). Regeneron confirmed it is planning additional regulatory submissions in further international territories, including Japan.
