A new kind of drug to fight Alzheimer's has shown promise when given to people in the early stages of the disease, drug-maker Eli Lilly said Wednesday.

Known as solanezumab, the drug is a monoclonal antibody that helps the brain clear amyloid-beta before it clumps together to form plaques that are implicated in Alzheimer's, which affects 44 million people living with dementia worldwide, and has no effective treatment.

In 2012, solanezumab was shown to be no better than a sugar pill in clinical trials.

An editorial in the New England Journal of Medicine in 2014 said that as many as one quarter of patients studied in the early trials may have had dementia but not Alzheimer's, and that scientific trials should continue in people with confirmed Alzheimer's.

This time, researchers reported on randomized, double blind trials involving 1,322 people with mild Alzheimer's disease.
Some were given the drug right away, others after a period of two years. Both doctors and patients were unaware of whether they were using a sugar pill or the actual drug.

When researchers compared the cognitive function of the two groups two years into the study, the difference was "statistically significant," Eli Lilly said in a statement.

The study is published in the journal Alzheimer's and Dementia: Translational Research and Clinical Interventions, and was discussed at the Alzheimer's Association Annual Conference in the US capital.

"Today's findings strongly suggest that targeting people in the earliest stages of Alzheimer's disease with these antibody treatments is the best way to slow or stop Alzheimer's disease," said Doug Brown, head of research at the Alzheimer's Society.

"After a decade of no new therapies for dementia, today's news is an exciting step forward."

- Experts urge caution -

More study is needed to understand the risks and benefits of the drug, experts said. The final results from the current study are expected in 18 months.

Some researchers urged caution in interpreting the results.

"These reports are good news in the same way that a forecast of sunny weather at the weekend is good news. It raises hopes for good weather, but it does not mean good weather is a certainty," said John Hardy, professor of neuroscience at University College London.

Peter Roberts, emeritus professor of pharmacology at the University of Bristol, lamented early media reports that hyped the findings.

"I would very cautiously go along with this announcement possibly being significant, though unfortunately in the media this morning we have the usual 'medical breakthrough' spin," he said.

"Whether or not solanezumab proves to be disease-modifying will take some time to establish. The published data so far show only a small statistically-significant effect in the subset of mild cases of AD (not all the mild cases)," he said in a statement.

"The cognitive benefits are not astounding and are actually little or no better than the currently prescribed anticholinesterases."

Tara Spires-Jones, an Alzheimer's expert at the University of Edinburgh, agreed.

"Current results show the drug only achieves small improvements in early stages; however if it proves to be disease modifying in the current phase 3 trial and provides long term benefits, it will be a huge step forward from the current treatment options."