(NaturalNews) Elan Corp. and Transition Pharmaceuticals have called a premature halt on trials on the two highest doses of their experimental Alzheimer's drug ELND005 after the deaths of nine study participants.
"Greater rates of serious adverse events, including nine deaths, were observed among patients receiving the two highest doses. A direct relationship between ELND005 and these deaths has not been established," the companies said.
The announcement was greeted as particularly bad news for Elan, which recently had to update the safety label of its multiple sclerosis drug Tysabri after studies showed a heightened risk of death among patients taking it.
Elan and Transition had already completed a successful Phase I trial of the new drug, which showed that it built up in high concentrations in the brain and appeared to preserve higher levels of a key nerve-protecting enzyme. In the Phase II trial, the companies had been testing 353 people with either 250 milligram, 1,000 milligram or 2,000 milligram doses of the drug.
The decision to halt the two higher-dose trials was made in consultation with the study's Independent Safety Monitoring Committee. As no deaths were seen in the 250 milligram group, those tests will continue.
Although there was little effect on the companies' stock prices, analysts predicted an uphill battle for approval of the experimental drug.
"This is a considerable blow for the progress of the drug," Ian Hunter of Goodbody said.
"At the very least, efficacy at the lower dose will need to be compelling to justify development and ultimate approval," said Jack Gorman of Davy Stockbrokers.
Elan is also developing another Alzheimer's drug, this one in partnership with Johnson & Johnson, but progress on that product is not nearly as advanced.
Alzheimer's disease is the most common form of dementia, affecting more than five million people in the United States alone. The disease is characterized by a progressive loss of cognitive function, and is currently incurable. An Alzheimer's drug has been called the "holy grail" for pharmaceutical companies, but so far no effective cures seem forthcoming.