Shire expressed confidence that its new products would compensate for the loss in revenues after the arrival of a generic competitor to one of its bestselling medicines dented sales.

In April, Teva, the generics maker, began shipping a low-cost version of Adderall XR, Shire’s treatment for attention deficit and hyperactivity disorder, causing sales of the drug to fall by 77 per cent, and wiping $229m off the group’s top line.