Why is Regeneron’s Pasatru FOP approval commercially limited despite clinical promise?

Regeneron’s Pasatru won FDA approval for FOP with strong phase 3 data, including major reductions in new bone lesions and flare-ups in adults. But the launch math is tight because only about 220 adult U.S. patients are currently eligible, and rare-disease launches still face diagnosis, referral, and uptake hurdles.