By Agence France-Presse
Shares of Biogen were in free-fall on Thursday after it halted clinical trials for a medication once thought to offer promise for treating Alzheimer's disease.
Near 1435 GMT, shares of Biogen were down more than 28 percent at $230.49.
Biogen said it pulled the plug on phase three trials of aducanumab, which had been intended for patients with mild cognitive impairment and mild Alzheimer's disease dementia.
The trials, conducted jointly with Japanese company Eisai, were ended because they "were unlikely to meet their primary endpoint upon completion," Biogen said, adding that the decision was not due to "safety concerns."
"This disappointing news confirms the complexity of treating Alzheimer's disease and the need to further advance knowledge in neuroscience," said Biogen Chief Executive Michel Vounatsos.
Vounatsos pledged to "continue advancing our pipeline of potential therapies in Alzheimer's disease and innovative medicines for patients suffering from diseases of high unmet need."
The news follows Roche's announcement in January that it was halting two studies of another potential early Alzheimer's treatment after "disappointing" results but pledged to continue with other clinical trials to address the malady.
Alzheimer's Disease, a chronic neurodegenerative ailment that erodes memory, has been estimated to affect 50 million people worldwide, and the number of sufferers is rising.
But experts caution that the figures may underestimate the number of people affected because some have not been diagnosed.
Some estimates have said the Alzheimer’s population could reach 131 million in 2050.