New data shows an experimental drug could help some people with early stage Alzheimer's.

The medicine, lecanemab, attacks the protein amyloid that builds up in the brains of people with Alzheimer's, slowing progression of the disease.

There are side effects for some such as brain swelling and researchers are clear more work is needed.

Alzheimer's New Zealand Chief Executive Catherine Hall told Mike Hosking it's early days.

She says it's an intravenous injection once a fortnight for 18 months and there's a long way to go to see if it's worthwhile.

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