Gene therapy at $3.5m a dose approved for US adults with hemophilia B

Hemgenix frees patients from repeated treatments but initial cost makes it most expensive medicine in the world

US drug regulators have approved a one-off gene-therapy treatment for adults with the genetic blood disorder hemophilia B that frees patients from repeated treatments but costs $3.5m a dose, making it the most expensive medicine in the world.

The US Food and Drug Administration (FDA) approved CSL Behring's hemophilia B gene therapy Hemgenix on Tuesday. It cuts the number of bleeding events expected over the course of a year by over half, a study found, and frees 94% of patients from the need for regular infusions to control the condition.