The NHS spending watchdog has been ordered to reconsider evidence surrounding drugs that slow the progression of Alzheimer's disease, following successful appeals lodged by their manufacturers.

Donanemab and lecanemab were both licensed for use in the UK in 2024, yet were denied NHS availability after the National Institute for Health and Care Excellence ( Nice ) ruled their benefits were "too small" to justify the cost.

The treatments were estimated to cost five to six times more than the threshold Nice can normally recommend.

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However, the watchdog must now revisit its final draft guidance after appeals were brought forward by Eli Lilly, which makes donanemab, and Eisai, which makes lecanemab.

Key issues to be reconsidered for both drugs include conclusions regarding the quality of life of Alzheimer's carers, along with evidence submitted by NHS England estimating the cost of administering the treatments via infusion.

The pharmaceutical firms argued that the document detailing infusion costs was only handed over four days before the third committee meeting, leaving little time for adequate scrutiny.

According to Lilly, Nice will also re-examine evidence relating to unpaid carer costs and long-term data on donanemab.

Both donanemab and lecanemab are targeted antibody treatments that bind to amyloid, a protein that accumulates in the brains of Alzheimer's sufferers.

This process helps to clear the build-up and reduces the rate of cognitive decline. The medications mark a significant breakthrough as they address the underlying cause of the condition rather than just its symptoms.

Nice published its final draft guidance on donanemab and lecanemab in June last year.

It said the treatments have been shown to delay progression from mild to moderate Alzheimer's by four to six months, but the medicines cannot be provided on the NHS because they are not good value for money and "only provide modest benefits at best".

Responding to the appeal's outcome, Chris Stokes, general manager of the northern European hub at Lilly, said: "This is a big moment in the battle against Alzheimer's disease.

"Nice was right to look again at the evidence in front of them and it's welcome that our appeal has been upheld. For people living with Alzheimer's disease, and for the families and carers who support them, this matters, perhaps now more than ever."

An Eisai spokesperson added: "This news offers a welcome glimmer of hope for the Alzheimer's disease community in England.

"We are keen to work quickly with Nice to assess this treatment effectively, because whilst we wait, Alzheimer's disease does not."

Helen Knight, director of medicines evaluation at Nice, said: "The independent appeal panel has ruled that some elements the committee used to inform its decision-making in relation to the cost effectiveness of donanemab and lecanemab need further consideration.

"So today we have announced we will give stakeholders an opportunity to provide more information for the committee to help it address the areas of continuing uncertainty highlighted by the appeal panel.

"Throughout our assessment of donanemab and lecanemab we have done everything we possibly can to try and achieve a positive outcome, including providing an additional opportunity for evidence to be submitted.

"Today's decision underlines our commitment to continuing that process."

Michelle Dyson, chief executive at Alzheimer's Society, responded: "We welcome Nice's decision to look again at the case for lecanemab and donanemab, particularly at the significant impact of dementia on unpaid carers.

"We know that carers are too often pushed to breaking point and this needs to be properly recognised.

"People living with dementia are desperate for new treatments that delay the progression of symptoms and help them stay independent for longer.

"The science is moving fast and globally more people are starting to access these drugs, but the UK is falling behind. With over 30 Alzheimer's disease drugs in late-stage clinical trials, there are likely to be more treatments submitted for approval soon."