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FDA says not yet to Ipsen rare bone disease drug

French drugmaker Ipsen announced last week that the FDA had responded to the New Drug application for its fibrodysplasia ossificans progressiva (FOP) therapy, palovarotene, with a Complete Response Letter.

According to the company’s statement, the CRL is related to a previous request that the agency had made for additional information on palovarotene’s clinical data. The request had been communicated in October 2022, and Ipsen anticipates responding within the first quarter of next year. While no specific details were disclosed concerning the data requests, Ipsen said it is “not a request for additional efficacy or safety data beyond existing studies.”

Palovarotene belongs to a class of medications known as retinoids, similar in mechanism to other drugs which are derivatives of vitamin A. The oral drug was first approved for use in Canada in January 2022, making it the first global approval for any FOP therapy. While it has received Rare Pediatric Disease and Breakthrough Therapy designations from the FDA, its road to approval in the United States has been bumpy, to say the least. FOP is a rare, bone and tissue disorder that causes bone formation outside of the skeleton and in connective tissue.

The drug was initially developed by Canadian biopharma Clementia and was perhaps the most important incentive to Ipsen when it decided to buy all outstanding shares of the company in 2019, looking to bolster its rare disease portfolio.

In May 2021, Ipsen confirmed that the FDA had accepted its NDA for the drug, only to announce a few months later that the application had been withdrawn. At the time, the company said that during the review and ongoing dialogue with the FDA, “it was recognized that additional analyses and evaluation of data collected from Ipsen’s Phase III MOVE and FOP program would be required to progress.”

It was agreed between Ipsen and the FDA that it would not be possible to complete this within the current NDA review cycle Since then, the drug received a Priority Review in January 2022. Now, due to pending requests, the FDA will be evaluating the resubmission of the NDA once more.