Researchers also believe that the treatment could one day be used like statins, with a single jab given to patients before they start showing symptoms of the disease.
Dr Eric Karran, director of research at Alzheimer's UK, has said they were "full of hope" that the drug, which could help "unlock" the secrets of the disease, will be made available to people before the end of the decade.
He said in a conference that if solanezumab is shown to work in mild Alzheimer's disease then the pathway would be to take that earlier.
The drug works by targeting a toxic protein in the brain called beta amyloid, which can build up for a decade before any outward signs of dementia such as memory loss.
Karran said that if its combined with a battery of early detection tests involving scans and memory, treatments could one day lead to "biomarker" tests to accurately spot those at risk before the disease strikes.
People aged between the age of 55 to 90 are being recruited for a study in the US, to examine the drug's effects in people with mild Alzheimer's.