Shares in pharmaceutical giant AstraZeneca PLC (LSE:AZN) fell 8% on Monday, erasing £14bn from the company's market value by the close.
The drop comes amid investor concerns over the results of a high-profile study of its new cancer drug, datopotamab deruxtecan (Dato-DXd).
While the drug helped lung cancer patients live longer without worsening symptoms compared to standard chemotherapy, the trial's success and the drug's overall survival benefit lacked clarity, analysts said. There were also safety concerns.
Analysts at Jefferies said the results fell short of the best-case scenario, with the American investment bank's analysts noting that the data showed a "less pronounced benefit than hoped".
At the close, AZN shares were changing hands for 10,374p, down 896p on the day.
*** Update: Closing share price added. ***