AstraZeneca PLC (LSE:AZN) shares fell more than 1.7% on Tuesday after the UK healthcare watchdog said that it could not recommend the drug company's breast cancer drug for the NHS.
The National Institute for Health and Care Excellence (NICE) said it was unable to recommend Enhertu for use in NHS England for advanced common form of breast cancer, HER-2-low breast cancer.
Helen Knight, NICE's director of medicines evaluation, said the medicines watchdog was "deeply disappointed" to make the decision due to its high cost.
It was the first time in six years that a breast cancer treatment had been deemed too costly by the public health body, with NICE having warned in March that it thought the drug did not provide value for money.
Last week, AstraZeneca boss Pascal Soriot called for the UK government to reassess the funding of new medicines.
Enhertu generated $1.7 billion in total sales in the first half of the year.
The drug costs £1,455 per 100 mg vial, while a course of treatment costs around £117,857 at the 'list price', although the NHS can access a discounted price.
Enhertu is still available in Scotland.