Research

Dementia research trials: What is trontinemab?

What is trontinemab?

Trontinemab, developed by Roche, is a disease-modifying drug, which means it was developed to tackle the root causes of Alzheimer's disease, rather than helping with its symptoms.  

Trontinemab is delivered into the vein directly through an IV bag, also known as intravenously. It is an immunotherapy. Immunotherapies use the body’s immune system and are often used in cancer to target and destroy cancerous cells.  

In Alzheimer’s disease, immunotherapies are used to recognise and target the toxic proteins that build up in the brain. Trontinemab targets amyloid plaques, build-up of amyloid protein that clumps in the brain, and is a key characteristic of Alzheimer’s disease. The build-up of these proteins is toxic to brain cells, slowing them down and eventually killing them. The slowing down and death of brain cells then causes the symptoms of Alzheimer’s disease.  

How does trontinemab work?

Trontinemab works in a similar way to other antibody treatments, like lecanemab and donanemab, where the antibody recognises and binds with amyloid beta in the brain. This causes the brain’s immune cells to clear amyloid that has built up from the brain. One of the issues with developing treatments for Alzheimer’s disease is getting the drug across the blood brain barrier – a tightly packed layer of cells that protects the brain.

Trontinemab has been designed with a protein attached to the antibody, which helps it cross the blood brain barrier more easily. Roche are calling this Brainshuttleᵀᴹ.

Researchers are now working to get new drugs across the blood brain barrier more easily.

Results from trontinemab clinical trials

In July 2025, Roche, the company that developed trontinemab, shared the results of their phase 2 clinical trial that was carried out in people with early-stage Alzheimer’s disease or had mild cognitive impairment. The trial called 'Brainshuttle AD', showed that amyloid was cleared in nine out of ten people within 28 weeks. 

This means that amyloid plaques, one of the key characteristics of Alzheimer's disease, had been removed.  

These phase 2 trial results are promising, especially as amyloid was cleared from the brain quickly. 

The trial did not investigate whether the changes in the brain meant Alzheimer’s disease progression was slowed or if people’s thinking and memory were improved. This is common for phase 2 trials, which are often designed to test different doses, to see which is most effective, and monitor people carefully for side effects.

Are there any side effects?

Like all drugs, trontinemab has some side effects. One of the more serious side effects of antibody treatments against amyloid, like trontinemab, is swelling or microbleeds on the brain. These are known as Amyloid-Related Imaging Abnormalities (ARIA).  

Some of the safety data about ARIAs has been presented at scientific conferences. Four people on the phase 2 trial (less than 5%) showed signs of ARIA detected through MRI brain scanning. Only one of these people had symptoms of ARIA, which were mild.

The full results of side effects from the phase 2 trial have not yet been published. 

What happens next

Researchers are now testing trontinemab in phase 3 clinical trials to test whether it is effective at slowing Alzheimer’s disease in a broad range of people. Around 100 people were involved in the phase 2 trial, whereas both of the initial phase 3 trial recruitment aims to enrol around 800 people.

The next trontinemab trial is taking place across 18 countries, including the UK, where Alzheimer’s Society nurses are supporting recruitment.

We expect to hear results from the phase 3 trontinemab trial when it ends in 2028. After the trial is finished, if the results are positive, drug regulatory bodies will need to decide whether trontinemab is safe and effective before it would be available in the UK.