Eisai shares fell the most in 16 months following a report of a second death potentially linked to the groundbreaking experimental drug for Alzheimer’s disease it is developing with Biogen.

The case involved a 65-year-old woman who died of a massive brain hemorrhage after suffering a stroke and a type of brain swelling and bleeding in an Eisai trial, according to a report in Science magazine. The bleeding began after the patient received an anti-clotting drug, the report said. Brain swelling and bleeding have previously been linked to medicines that work like the Biogen-Eisai treatment.

Bloomberg