A gene therapy designed to treat the severest cases of the most common type of hemophilia has been rejected by the FDA, which wants more data on the durability of the investigational treatment developed by BioMarin Pharmaceutical.

Letters issued by the FDA turning down experimental treatments aren’t made public, but BioMarin (NASDAQ: BMRN) says the missive requested data that the agency hadn’t previously told it the company would need to support approval of the bleeding disorder drug, valoctocogene roxaparvovec (Roctavian).

Shares of San Rafael, CA-based BioMarin closed down 35 percent Wednesday at $76.71. In an SVB Leerink research note analysts… Read more »