The Therapeutic Goods Administration (TGA) has decided not to register Lecanemab, an Alzheimer’s drug that has been shown to reduce , for use in Australia.
Trials of the drug in the UK showed it slowed a person's cognitive decline by around one-quarter to one-third.
Subsequently, Lecanemab was approved for use in the United Kindgom, the United States, and a number of other countries.
It is the that modifies the disease — and not just the symptoms — of the most common form of dementia
But the TGA said on Wednesday: "The demonstrated efficacy did not outweigh the safety risks associated with the use of this medicine" in explaining why it wouldn't register the drug.
Dr Emer MacSweeney runs the private company that led the UK Lecanemab trial, which tested the drug on people with Alzheimer's, the most common form of dementia.
"Any medications that can slow this process and also which herald the beginning of a new era of other new medications designed to be possibly able to stop this disease in its tracks is very big news," she said.
But MacSweeney acknowledged the drug can have fatal consequences and can cause swelling or bleeding in the brain.
This is a side effect called ARIA, which stands for amyloid-related imaging abnormalities.
"[A] ballpark 35 per cent of people taking this class of medication will develop ARIA, but only about 3.5 per cent of people will actually experience any symptoms," she said.
"A small group of people, about 0.6 per cent, can actually develop more serious side effects."
What was behind the TGA decision?
The TGA acknowledged the drug improved patient outcomes when compared to a placebo but said the safety risks were too great.
"... the demonstrated efficacy did not outweigh the safety risks associated with the use of this medicine," it said.
"In particular, the TGA delegate considered the frequent occurrence of amyloid-related imaging abnormalities (ARIA) in patients."
The sponsor of Lecanemab, Eisai Australia, says it intends to request a reconsideration of the TGA's decision.
It's not the first time the drug has been rejected by a regulator.
In July the European Medicines Agency refused market authorisation of the drug, saying: "the benefits of treatment are not large enough to outweigh the risks".
"Although most cases of ARIA in the main study were not serious and did not involve symptoms, some patients had serious events, including large bleeds in the brain which required hospitalisation. The seriousness of this side effect should be considered in the context of the small effect seen with the medicine," it said.
Lee-Fay Low, a professor in ageing and health at the University of Sydney's Faculty of Medicine and Health labelled the decision "disappointing".
"While there have been risks associated with the drug, it would have been a benefit to people with mild cognitive impairment or early Alzheimer’s disease and has shown promising results for people in these groups," she said.
"It is important that we take a public health approach to dementia prevention. Exercise, reducing cholesterol and lowering blood pressure, as well as staying active into older age, can all play a part in reducing the risk of dementia.
"The government should also invest in memory clinics and increase capacity for early diagnosis and post-diagnosis support.”
Drug a 'historic first step'
Dementia Australia CEO Professor Tanya Buchanan says the decision deprives Australians the right to choose.
"Lecanemab is not a cure and is not for all people with a diagnosis of Alzheimer's disease. Like many medicines it also comes with some significant risks," she said.
"It is however, widely seen as an historic first step towards reducing the huge impact of Alzheimer's disease and for people living with the condition it signified hope."
Buchanan described the TGA rejection as disappointing but said there is ongoing investment into Alzheimer's and dementia research.
"There are currently more than 100 clinical trials of medicines to manage dementia happening globally. Research released this year also showed that nearly half of all dementia cases globally could be prevented by addressing modifiable risk factors."
