Meanwhile, the Allon Therapeutics drug helped improve some measures of short-term memory in patients with mild cognitive impairment, a condition that often leads to Alzheimer's disease.
The researchers reported they found the retrovirus XMRV in a majority of 101 patients with chronic fatigue syndrome, a debilitating condition that involves cognitive dysfunction and severe pain.
All three companies are also looking at whether their drugs work in a condition called mild cognitive impairment--mild memory loss that may or may not be a precursor to Alzheimer's or other dementia.
While cholinesterase inhibitors are useful in many early dementias, studies have not shown that treatment of patients with mild cognitive impairment, which is the condition before dementia, prevents or slows progression to dementia.