Garetosmab

iStock, nambitomo Regeneron’s Pasatru is the second fibrodysplasia ossificans progressiva drug approved in the U.S., following the 2023 approval of Ipsen’s Sohonos. Regeneron has won FDA approval for garetosmab in fibrodysplasia ossificans progressiva, giving the biotech a commercial product built on its scientific breakthrough in the ultrarare disease. It also sets up a showdown with Ipsen, which owns the only other FOP drug on the market. The Thursday approval covers the use of Pasatru—an antibody called garetosmab and REGN2477 during development—to reduce the formation of new heterotopic ossification (HO) lesions and clinician-assessed flare-ups in adults with FOP. HO is characterized by bone developing in soft tissues. Pasatru is the second FOP drug to secure U.S. approval. The first, Ipsen’s Sohonos, came to market in 2023 after a troubled development program marked by clinical and regulatory setbacks. Ipsen acquired the asset in 2019 from Clementia Pharmaceuticals. For the first half of 2026, Sohonos contributed to the €11.4 million ($13.4 million) in sales generated by Ipsen’s rare disease drugs apart from Iqirvo and Bylvay. Following Clinical Hold and Trial Setback, Ipsen Takes $728 Million Hit on FOP Drug Ipsen’s decision to pause dosing in its studies of palovarotene trials for patients with fibrodysplasia ossificans progressive (FOP) has hit the France-based company right in the pocketbook. February 13, 2020 · 2 min read · Alex Keown Read more Regeneron has now won approval based on Phase 3 trial data that showed two doses of Pasatru reduced the total number of new HO lesions compared to placebo. Investigators saw 19 new lesions in the 21 patients on placebo, compared to three new lesions in the 42 patients treated across two Pasatru dose cohorts. The recommended starting dosage is 10 mg/kg, the higher of the two doses given in the Phase 3 trial. Patients receive the antibody intravenously for one hour every month. If a patient doesn’t tolerate the dose, they can drop down to the lower Phase 3 dose, 3 mg/kg. Patients on the lower dose still receive a 60-minute infusion once monthly. Regeneron designed Pasatru to be given in a range of care settings, including at home when appropriate. The flexibility reflects the significant mobility challenges faced by many people with FOP, which can make walking difficult as bone builds up in muscles, tendons, ligaments and other connective tissues. Most patients are wheelchair-bound by age 30, Regeneron said. Regeneron’s efforts in the disease can be traced back to 2015, when researchers published a paper describing an unexpected discovery about the driver of HO in FOP. By looking at FOP in mice, Regeneron identified Activin A as the ligand responsible for HO. Regeneron started a Phase 1 trial of the anti-Activin A antibody—now known as Pasatru— in 2016. About 900 people are diagnosed with FOP. Rare disease–focused biopharma Mirum Pharmaceuticals has predicted that its rival FOP drug candidate, zilurgisertib, could generate peak sales of more than $200 million. Zilurgisertib, which Mirum licensed from Incyte, is under review at the FDA and has an approval decision date of Sept. 26. Mirum is seeking approval of zilurgisertib for the treatment of FOP in patients 12 years of age and older. Regeneron’s Phase 3 study only enrolled adults, although the company plans to start a trial in children and adolescents this year.

Dive Brief:The Food and Drug Administration on Wednesday approved Regeneron Pharmaceuticals Pasatru to treat an uncommon bone disease, ushering in a commercial battle with an Ipsen drug that hasnt sold well since its launch.Pasatru is cleared for fibrodysplasia ossificans progressiva, or FOP, a degenerative condition that causes muscles and connective tissue to turn into bones. The disease is estimated to occur in about 1 in a million people and leads to a loss of mobility.Development of Pasatru was slowed by a study pause following the deaths of multiple trial participants. Regeneron investigated, concluded that the treatment likely wasnt the cause and advanced the treatment into late-stage testing. Phase 3 results announced last September showed that, over the course of a year, the drug reduced new abnormal bone formations by 90% or morewhen compared to a placebo.Dive Insight:Pasatru will have an average annual, per-patient list price of about $1.4 million based on the enrollees in clinical studies, according to a Regeneron spokesperson. The drug is dosed at either 3 or 10 milligrams per kilogram of body weight, so the cost could total anywhere between $693,000 and $2.1 million, the spokesperson said.Known scientifically as garetosmab, the treatment is an antibody drug that blocks the activity of a protein called Activin A, which triggers excessive bone growth in people with the disease.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,said Michelle Davis, executive director of the International FOP Association, in a statement.Pasatru will challenge Ipsens Sohonos, which gained an approval in 2023 despite questions about its benefits and safety. Though the drugs havent been tested head-to-head, Sohonos was associated with less of an impact on bone growth. Prior to Sohonos approval, FDA scientists also expressed concerns that patients taking the drug might be more likely than placebo recipients to experience the inflammatory flare-ups that come before abnormal bone growth.Sohonos recorded sales of 21 million euros, or $24 million, in the first six months of 2026, roughly equal to the same period in 2025. Ipsen recorded an impairment charge of 279 million euros in 2024 related to slower-than-expected sales.Pasatrus launch comes as Regeneron is facing fresh questions about its future. The companys biggest seller, the eye drug Eylea, is facing growing biosimilar competition. Sales of a high-dose version of Eylea havent yet met investor expectationsand an up-and-coming cancer drug missed its goalin a key clinical trial. '