CAR T-cell therapy

CAR T-cell therapy uses immune cells called T cells, which normally find and kill infections. They're reprogrammed in the lab so they can find and kill specific cells instead. They’re then put back into the body where they multiply and attack the cells they're designed to target.  

In MS, these CAR T-cells are reprogrammed to target B cells, a type of immune cell. In MS, B cells are thought to mistakenly attack the protective myelin coating around nerves in the brain and spinal cord.  

Researchers are studying two types of CAR T-cell therapy:

• Autologous CAR T-cell therapy: T cells are collected from the person’s own blood, reprogrammed in the lab, and then given back. Most of the early studies in MS use this approach.
• Allogenic CAR T-cell therapy: T cells are taken from a healthy donor, reprogrammed in the lab and then given to the person with MS.

This approach has the potential to slow or even stop MS progression. But this is still being tested in early trials. 

CAR T-cell therapy is currently being investigated for MS in small, early-stage clinical trials. These trials will check whether the treatment is safe and tolerable for people with MS. They'll also be looking for early signs of potential benefit. If the results from these trials are promising, larger trials will be needed to test how effective these therapies are, and how they compares with existing MS treatments. 

Read more about how treatments for MS are developed

AUTO1-MS1 

This is a phase 1 clinical trial that began in 2025. The team aim to recruit 18 people globally with relapsing or progressive MS who aren’t responding to current treatments. The trial will test whether an autologous CAR T-cell therapy is feasible and safe for people with MS. The trial is due to finish in 2029. Participants will be closely monitored for 24 months and there will be a long-term follow-up phase of up to 15 years. 

Breakfree-2 

This is a phase 1 clinical trial taking place at multiple sites across the world, including four in the UK. The trial is testing whether an autologous CAR T-cell therapy, developed by biopharmaceutical company Bristol Myers Squibb, is safe for people with relapsing or progressive MS. The team aims to recruit 120 people, who will be closely monitored for 24 months. The study is due to finish in 2027. 

KYV-101 

KYV-101 is an autologous CAR T-cell therapy developed by the biopharmaceutical company Kyverna. This is a phase 1 clinical trial based in the US. The team aims to recruit up to 10 people with primary or secondary progressive MS who haven’t responded to therapies to slow progression. They’re looking at whether the therapy can enter the brain and spinal cord, and which dose is safest.  

They presented encouraging early results from the first four trial participants at ECTRIMS 2025. Their results suggest that KYV-101 can cross into the brain and spinal cord and is well-tolerated with no serious side effects. All four participants showed stable or improved disability scores and a substantial improvement in fatigue after 12 months. The trial is due to finish in 2029.

NCT06680037 

This is a phase 1 study taking place across the US. Researchers are testing if genetically engineered donor T-cells (allogenic) can safely and effectively target the immune cells that drive inflammation and damage in MS. Researchers are recruiting up to 32 people with progressive MS. The study is due to finish in 2029. 

CAR T-cell therapies are still in early clinical trials, so we still don’t know all the risks for people with MS. But we do know some of the potential side effects from their use in cancer treatment. These are usually reversible and treatable but can be serious if not managed early: 

• Cytokine release syndrome: This happens when the immune system releases a large number of cytokines (small proteins that tell immune cells what to do) into the bloodstream. It causes symptoms like the flu, with fever, low energy and body aches. In rare cases this inflammation can damage organs and tissues.
• Immune effector cell-associated Neurotoxicity syndrome: This happens when the activated immune cells mistakenly attack the brain. It usually starts within a week after treatment and can cause symptoms like confusion, seizures and trouble speaking.
• Infection: Because CAR T-cells target B cells, a type of immune cell that helps to fight infections, this treatment can leave people more vulnerable to infections. 

Many existing MS treatments, including ocrelizumab, work by targeting B cells. So do BTK inhibitors, which are currently being tested in trials. These treatments need to be given regularly to keep B cell numbers low. 

CAR T-cell therapy might offer longer-lasting effects, potentially even as a one-off treatment. And unlike most existing MS treatments, CAR T-cells can cross the blood brain barrier. This is the protective border of cells that controls which molecules can enter the brain and spinal cord from the blood. This means they could fight immune cells more effectively, at the location where they’re causing damage.   

Like HSCT (stem cell transplant), CAR T-cell therapy aims to ‘reset’ the immune system. But while HSCT rebuilds the immune system using stem cells, CAR T-cell therapy uses reprogrammed T cells to specifically target B cells. This could offer a more precise approach.   

But CAR T-cell therapy would only target the immune system. That’s why it’s important that we continue to fund research to find treatments that can target other aspects of MS – like repairing myelin that has already been damaged and keeping nerves healthy.   

You can find out more information about CAR T-cell therapy clinical trials for MS on the NIHR Be Part of Research website, or by speaking to your neurologist.