Pharmaceutical company Eli Lilly has announced that a very large clinical trial for a drug called solanezumab for Alzheimer's disease has failed.

This was a repeat of an earlier clinical trail of this drug, but this time they were testing it in patients with early-stage Alzheimer's disease.

The results were highly anticipated, not only because of hope for people with dementia, but also because, if the drug had succeeded, it would have demonstrated that beta amyloid contributes to the cause of Alzheimer's disease, a major but recently controversial theory in the field.

This is disappointing news for families who are watching Alzheimer's rob their loved ones of their memories and emotions - it consumes and absorbs families.

There are more than 353,800 Australians living with dementia, and the costs of managing the disease are expected to rise to $83 billion by the 2060s, representing around 11 per cent of Australia's health and residential aged care sector spending.

Importantly, this isn't the end for beta amyloid theory. There's a trial of another important drug for Alzheimer's, aducanumab, being run by Biogen [another pharmaceutical company] which has shown interesting and encouraging signs.

And there are numerous other trials in the pipeline of drugs which act in a variety of different ways to try to slow or reverse Alzheimer's.

There's good reason to have hope and optimism that a treatment will become available for this devastating disease in our lifetimes.