People with Alzheimer’s disease are missing out on experimental treatments because they are not diagnosed early or accurately enough to be enrolled in clinical trials, a UK charity has said.

Trials of Alzheimer’s drugs reached a record high this year, according to data published on Tuesday, but Alzheimer’s Research UK said too few UK patients were taking part because their diagnoses were delayed or were not specific enough.

The warning suggests patients are being left behind as research gathers momentum and branches out to tackle the condition on multiple fronts, a strategy that scientists consider to be crucial for halting the disease.

Dr Sheona Scales, the director of research at Alzheimer’s Research UK, said the recent surge in clinical trials was driving demand for participants, but without a large and diverse range of patients to match to trials the UK risked missing out. “People won’t have access to the next generation of Alzheimer’s treatments,” she said.

More than 32 million people worldwide have Alzheimer’s disease, the most common form of dementia, but getting a diagnosis can take years. One in three people living with the condition in the UK do not have a formal diagnosis.

The precise mechanisms that drive Alzheimer’s disease are unclear but hallmarks include the buildup of abnormal proteins in the brain, including amyloid plaques between cells and tangles of tau protein inside neurons.

Hopes for treating Alzheimer’s have been boosted by the arrival of the anti-amyloid medicines lecanemab and donanemab, which have been approved by medicines regulators around the world. Clinical trials found that both slowed the progression of the disease, though the benefits were slight and neither drug was considered cost-effective for the NHS.

The recent Cochrane review of seven anti-amyloid drugs prompted controversy by concluding that the class of drugs had no clinically meaningful impact on patients over 18 months. But critics argued that the analysis lumped lecanemab and donanemab in with older, less effective medicines, and said the drugs may have better results when given to patients much earlier and for longer periods.

Dr Jeffrey Cummings, of the University of Nevada, has published an annual review of clinical trials for Alzheimer’s drugs for the past decade. The latest review, published in Alzheimer’s & Dementia: Translational Research & Clinical Interventions, reveals a shifting approach to the disease, with fewer drugs designed to remove amyloid and more targeting tau, inflammation and other immune system pathways.

Cummings said: “Anti‑amyloid medicines such as lecanemab and donanemab have been a crucial breakthrough. They’ve shown that directly targeting the disease’s process can slow decline. But they are only the beginning of what people with Alzheimer’s will ultimately need.”

The number of candidate drugs being trialled for Alzheimer’s has risen by 40% in the past decade, the review found, with 158 potential medicines and 192 trials taking place globally this year. Eight final phase-three trials are due to end in 2026.

Another keenly watched trial that could report this year is the Trailblazer-Alz 3 trial, which is testing the effect of donanemab in people who have amyloid in the brain but no Alzheimer’s symptoms. This could show whether the drug can protect against cognitive decline by administering the drug before the disease destroys brain cells.

Diagnosing patients is a major obstacle for identifying patients suitable for Alzheimer’s drug trials. In the UK, a third of patients have no formal diagnosis, and of those who do, the diagnosis is often general dementia, which is not precise enough to place people on trials. As such, fewer than 1,000 UK patients are taking part in phase 3 trials for Alzheimer’s drugs.

Scales said: “Progress depends on finding the right participants for these studies, and that starts with early and accurate diagnosis. Without it, researchers can’t match people to the trials most likely to help them.”