Lecanemab and donanemab slow down the early stages of the disease - which is the most common form of dementia.
But Alzheimer's Research UK says the NHS is not ready to roll out the drugs, which could be licensed this year.
The treatments would then be subject to an assessment of cost and benefits before they are made available.
Lecanemab and donanemab represent a step forward because they target one of the causes of Alzheimer's, rather than treating the symptoms.
However, their effectiveness depends on early diagnosis - and very few people have the specialist scans or investigations which would be needed.
Questions also remain over potentially harmful side-effects of the drugs and whether the benefit they offer represents value for NHS money.
Dawn, who's 62 and from Hampshire, is on a new donanemab trial, aimed at studying optimum dosing levels.
She started noticing memory problems last year, forgetting recent events and sometimes struggling to follow a television programme.
"I just knew something wasn't right," she says.
Tests revealed raised levels of a rogue protein in her brain called amyloid - a key marker of Alzheimer's disease.
Amyloid forms clumps or plaques around neurons, which are cells in the brain that transmit information and instructions throughout the body.
This process can start up to 20 years before the damage to brain cells becomes apparent and the first symptoms of dementia emerge, such as memory loss, or confusion.
Donanemab and lecanemab are antibodies, like those made by our body to attack viruses or bacteria. They have both been engineered to bind to amyloid and help our immune system clear it from the brain.
Dawn is hopeful the drug will help her: "If it slows it down, then I'll be able to function as I'd like to and do some of the things I'd still like to do."
In global trials involving hundreds of early-stage Alzheimer's patients, the drugs were shown to slow cognitive decline by between about a quarter and a third over 18 months.
Consultant neurologist Dr Cath Mummery, who is head of clinical trials at the Dementia Research Centre, University College London, says this would make a meaningful, if small, difference to individual patients: "Over 18 months, that gives you about five months at a higher function."
Lecanemab - produced by Eisai and Biogen - is already licensed in the US where it costs about £20,000 per patient per year.
The UK medicines regulator - the Medicines and Healthcare products Regulatory Agency (MHRA) - is assessing the drugs and is expected to approve lecanemab within the next few months, with the licence for donanemab - made by Eli Lilly - following slightly later.
However, both drugs come with potentially serious side effects, most notably swelling and bleeding in the brain. Three of the 853 people who took donanemab during the clinical trial, died as a result of the treatment.
As a result, patients need very careful monitoring via MRI brain scans.
The side effects of the drugs and their limited effectiveness has led some critics to dismiss them as a dead end.
Dr Cath Mummery disagrees.
She says, "For the first time, we've got drugs that show that you can alter the course of Alzheimer's disease, and that's an extraordinary thing."
Dr Mummery believes this may be the first move towards managing Alzheimer's as a chronic disease and keeping sufferers well and stable for as long as possible. Until now, she says, doctors could only give supportive and palliative care for what is, in effect, a terminal disease.
But even if the drugs are licensed in the UK, it does not mean they will be immediately available on the NHS.
The National Institute for Health and Care Excellence (NICE) and the Scottish Medicines Consortium will assess the effectiveness of lecanemab and donanemab, and whether they represent value for money.
A briefing paper for NHS England estimates that between 50,000 and 280,000 patients might be eligible for the new treatments if NICE recommends that the drugs are used by the health service. The cost of the drugs - and administering the treatment - would be between £500m and £1bn per year.
However, even if the drugs are approved, Alzheimer's charities say that the NHS is unprepared for their delivery.
This report was first published on the BBC website
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"Alzheimer’s is not about the past - the successes, the accolades, the accomplishments … Alzheimer’s is about the present and the struggle, the scrappy brawl, the fight to live with a disease. It’s being in the present, the relationships, the experiences, the courage to live in the soul”
- Anon
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