Shares in Novo Nordisk fell as much as 6% on Friday before recovering some ground later in the session, extending recent losses that threaten to wipe out all the gains since the drugmaker launched its blockbuster weight-loss treatment Wegovy four years ago.

Compounding pharmacies are crimping sales of Novo Nordisk's obesity drug Wegovy by making what are essentially copies of the name-brand medicine. The company says it trying to stop them.