Ipsen announced that the U.S. Food and Drug Administration (FDA) has accepted for Priority Review its resubmitted New Drug Application (NDA) for investigational palovarotene for the treatment of patients with fibrodysplasia ossificans progressiva (FOP), an ultra-rare genetic disorder. Ipsen is seeking approval of palovarotene, an oral, selective retinoic-acid receptor gamma (RAR?) agonist for the prevention of heterotopic ossification (HO; new bone formation outside of the normal skeletal system). The FDA has assigned 29 December 2022 as the Prescription Drug User Fee Act goal date, which is on track with anticipated regulatory submission timelines.

The FDA's Priority Review designation is assigned to investigational therapies that, if approved, represent a significant improvement in the safety or effectiveness of the treatment compared to the current standard of care. In January 2022, Health Canada was the first regulatory authority to approve Sohonos (palovarotene capsules) to reduce the formation of HO in adults and children aged 8 years and above for females and 10 years and above for males with FOP. Sohonos is approved in Canada for the treatment of patients with FOP for both chronic use and for flare-ups in these patient populations.

Palovarotene is not currently approved outside of Canada. A Marketing Authorization Application for palovarotene has also been filed in the E.U. in 2021, with responses to questions raised by the European Medicines Agency submitted in June 2022, in line with the ongoing regulatory process. Ipsen anticipates additional applications to other regulatory agencies in due course.

FOP has an estimated prevalence of 1.36 per million individuals; however, the number of confirmed cases varies by country. It is characterized by new bone formation outside of the normal skeletal system, like in soft connective tissues, a process known as HO,[3] which can be preceded by painful soft-tissue swelling or 'flare-ups'. Flare-up episodes are common and are a substantial contributor to the formation of new HO, however HO can form in the absence of a flare-up.

HO, once formed, is irreversible and leads to loss of mobility and shortened life expectancy.