Dublin-based pharmaceutical company Elan, along with Canadian-based Transition Therapeutics, has dropped the two highest doses of an experimental treatment for Alzheimer’s from clinical trials following the death of nine patients.

The company says no direct link between the deaths and the experimental treatment has been established but that it has decided to drop the high dose element of the trial over safety concerns.

The news raised doubts as to whether the drug will now get to market, industry analysts said, although the impact on Elan was limited as little value has so far been attributed to the product.

Patients will be withdrawn immediately from the Phase II study in the two higher dose groups, 1,000 milligrams and 2,000 mg dosed twice daily.

The study will continue unchanged for patients on 250 mg, the companies said.

“Greater rates of serious adverse events, including nine deaths, were observed among patients receiving the two highest doses. A direct relationship between ELND005 (the drug) and these deaths has not been established,” Elan and Transition said in a statement.

Elan and Transition, a small Toronto-based drugmaker, signed a worldwide development and commercialisation agreement in 2006 for the treatment.