Elan and Transition Therapeutics have announced that they will immediately withdraw patients from the two higher dose groups in the Phase II AD201 study for Alzheimer’s disease after nine deaths.

The AD201 study is evaluating three dose levels of ELND005 compared to placebo in 353 patients.

Patients will be withdrawn immediately from the study in the two higher dose groups, where each patient receives 1,000mg and 2,000mg dosed twice daily respectively, but will continue unchanged for patients who are assigned to the lower dose (250mg dosed twice daily) and placebo groups.

Greater rates of serious adverse events, including nine deaths, were observed among patients receiving the two highest doses, the companies said.