Patients could be getting breakthrough Alzheimer’s drug in a year, experts have said, but only a small proportion of patients will benefit unless more is done to boost dementia services in the NHS.

Experts estimated that unless there are drastic changes in UK dementia clinics, only 5% of patients eligible for the drug will be able to access it – and most of these will be private cases.

In September, scientists hailed a “historic moment” in Alzheimer’s research as a new drug was found to reduce memory decline among patients with early-stage disease.

Lecanemab, which is designed to target and clear amyloid – one of the proteins that builds up in the brains of people with Alzheimer’s, was found to slow decline in patients’ memory and thinking.

Scientists found that after 18 months the drug slowed the disease progression by 27% compared with patients taking the placebo.

Experts said that UK officials have much to do to prepare to deliver the drug, provided it gets regulatory approval.

The drug, created by Tokyo-based pharmaceutical company Eisai and US biotech firm Biogen, has been created for the treatment of mild cognitive impairment for patients with amyloid in the brain.

There are two ways to tell whether there is amyloid on the brain – a brain scan or biomarker test which is currently done through lumbar puncture.

While a blood test is on the horizon – dementia services must rely on these tests which are expensive and can have big waiting lists.

While private patients and those living near to big dementia services can access these diagnostic tests, the vast majority of the public cannot, experts said.

Experts warned that unless there are big changes in diagnostic services, people could become ineligible for Lecanemab treatment while on the waiting list for diagnosis because it can only be given to patients with mild disease – if their disease progresses to a moderate stage while on the waiting list, they will no longer be eligible for treatment.

More detail on the Lecanemab study will be presented to the Clinical Trials On Alzheimer’s congress in the US next week.

British experts expressed excitement over results from recent amyloid drug trials and said they were optimistic “that we’re seeing the beginning of Alzheimer therapies”.

But they warned that using Lecanemab in the UK would be “hard work”.

Speaking at a briefing ahead of the conference, Dr Susan Kohlhaas, director of research at Alzheimer’s Research UK, said: “The Lecanemab results brings a renewed sense of urgency to really improve the way we diagnose diseases like Alzheimer’s disease.”

Dr Liz Coulthard, associate professor in dementia neurology at the University of Bristol and North Bristol NHS Trust, added: “Over the years we have, as a profession, not used the biochemical definition of Alzheimer’s because we’ve not been able to test for it until after people have died.

“But we’ve now got biomarker tests that have come into the clinical sphere the last five years or so that we can actually diagnose people accurately with Alzheimer’s disease.

“So, if you work in a clinic where we don’t have biomarkers, the diagnostic accuracy for Alzheimer’s is about 70% – we cannot diagnose Alzheimer’s properly without doing biochemical tests.

“That’s not been a priority because there have been no molecular treatments, but now that there are, we need to start doing the biochemical tests on everyone.”

She added that the “vast majority of people” do not get a biomarker diagnosis and there is an “an enormous gulf between current service provision and what we need to do to deliver disease-modifying therapies”.

Dr Mani Santhana Krishnan, chair of the Old Age Faculty at the Royal College of Psychiatrists, added: “We need to get ready. It is about getting our current memory services robustly staffed and technically advanced.”

But Professor John Hardy, chair of molecular biology of neurological disease at the UCL Institute of Neurology, said that there was precedent for the NHS to quickly adapt to new therapies – citing the roll out of a multiple sclerosis treatment.

Professor Hardy estimated that patients could benefit from the treatment in the UK as early as next year.

“Of course, it depends upon regulatory authorities, but I would guess that we would see the first people towards the end of next year,” he said.

Asked what proportion of patients would benefit, Dr Coulthard said: “I would guess 5% – it would be given in the private sector because you’d be able to access biomarker and you’d be able to access biomarker tests (in the private sector).

“Then there are a few clinics in major cities who are doing biomarker tests now.

“It will be a small proportion of those who could be eligible, unless something changes.

“Or what will happen is we’ll have massive waiting times, but the trouble is people will wait beyond … I think it won’t be licenced in moderate disease.

“So people will be on a waiting list and by the time they come to see us, they’ll be a too advanced for the disease, which would be terrible.”