Can Regeneron (REGN)’s Rare-Disease Win Move the Earnings Needle?

Regeneron Pharmaceuticals, Inc. (NASDAQ:REGN) has won regulatory approval for Pasatru, a rare-disease treatment for fibrodysplasia ossificans progressiva (FOP), a genetic disorder where bone forms inside muscles, tendons, and ligaments. In a Phase 3 trial, the 3-milligram-per-kilogram dose showed a 94% reduction in new abnormal bone lesions compared to a placebo.

This is a significant scientific and regulatory victory for Regeneron, but its earnings potential is limited due to the exceptionally small market for FOP, estimated at one case per one million to one per two million people. Regeneron's existing franchises, such as Dupixent and Eylea HD, generate substantial revenue, making Pasatru's impact on the company's overall results relatively minor.

Despite this, the approval demonstrates Regeneron's ability to recover from a major clinical setback, validate the Activin A research platform, and recover from a major clinical setback. The company plans to launch a pediatric trial later in 2026, potentially expanding the eligible population. However, competition from Ipsen's Sohonos and other therapies could further limit Pasatru's market reach.

Hedge fund data shows that 72 funds held positions in Regeneron as of March 31, 2026, indicating cautious optimism about the company's long-term prospects.