Alzheimer’s Research UK has warned that patients are being shut out of clinical trials not because suitable treatments do not exist, but because the UK’s diagnostic system is too slow and too imprecise to connect them with research programmes in time. The warning lands at a moment when global investment in Alzheimer’s drug development is at its highest point on record.

The diagnosis problem is substantial. More than 32 million people worldwide are living with Alzheimer’s disease, the most common form of dementia, yet in the UK one in three of them have no formal diagnosis at all. Of those who do, a significant proportion receive a general dementia diagnosis rather than one specific to Alzheimer’s. That distinction matters enormously for trial eligibility. Most clinical research programmes require a confirmed Alzheimer’s diagnosis to enrol participants, and a catch-all dementia label does not meet that threshold. The consequence is visible in the numbers: fewer than 1,000 UK patients are currently taking part in phase three Alzheimer’s drug trials.

The research landscape they are being excluded from is expanding rapidly. The number of candidate drugs under investigation has risen by 40 per cent over the past decade. This year, 158 potential medicines are being tested across 192 trials globally, according to an annual review published in Alzheimer’s & Dementia: Translational Research & Clinical Interventions. Eight phase three trials are due to report results in 2026 alone. The direction of research is also changing. Fewer new drugs are targeting the amyloid protein that has dominated the field for decades, with more attention now turning to tau, inflammation, and immune system pathways, reflecting a growing consensus that the disease will need to be tackled on multiple fronts simultaneously.

The two drugs that have generated the most attention in recent years, lecanemab and donanemab, are both anti-amyloid medicines that have received regulatory approval in several countries after trials showed they slowed disease progression. Neither was judged cost-effective enough for routine NHS use. Their clinical standing has also been contested. A Cochrane review published recently concluded that anti-amyloid drugs as a class had no clinically meaningful impact on patients over an 18-month period. Critics pushed back, arguing the review bundled lecanemab and donanemab alongside older and considerably less effective medicines, and that the drugs may perform better when given earlier in the disease course and over longer timeframes. The debate is unresolved, but it has sharpened interest in earlier intervention.

That interest is reflected in one of the most closely watched trials currently under way. Trailblazer-Alz 3 is testing whether donanemab can protect against cognitive decline in people who carry amyloid in the brain but have not yet developed Alzheimer’s symptoms. The logic is that if the drug can be shown to prevent or significantly delay the onset of the disease, the case for treating patients before symptoms appear becomes much stronger. Results could arrive later this year.

Dr Sheona Scales, director of research at Alzheimer’s Research UK, said the surge in trials was driving demand for participants that the UK currently cannot satisfy. “Progress depends on finding the right participants for these studies, and that starts with early and accurate diagnosis,” she said. “Without it, researchers can’t match people to the trials most likely to help them.” The implication is that patients who are never properly diagnosed are not only missing out on trials today, they are also being positioned to miss out on the treatments those trials eventually produce.

The broader picture is uncomfortable. Alzheimer’s research is moving at a pace the UK’s diagnostic infrastructure is not keeping up with. That is not an argument against the research. It is an argument for treating diagnosis as urgently as the disease itself.

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