A single IV treatment retrains immune cells to fight autoimmune diseases in early trial

by Sanjukta Mondal, Medical Xpress

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CAR T-cell therapy is an immune-reprogramming procedure that turns a patient's own immune cells into cancer-fighting specialists. The entire process is complex, but researchers have now found a faster way to achieve similar effects using a single intravenous (IV) drip of a harmless engineered virus.

In the standard process, clinicians extract T cells from the patient's blood, then re-engineer them in the lab, arming each one with a chimeric antigen receptor (CAR)—engineered proteins designed to recognize specific markers on cancer cells. Once infused back into the patient, these modified T cells circulate through the body, identifying and eliminating the cancer cells they were engineered to target.

In this new off-the-shelf treatment, called JY231, researchers genetically engineered a harmless virus (lentiviral vector) whose sole job is to enter the body and deliver the genetic instructions needed to reprogram the patient's own immune cells directly inside the body. Sixteen patients who were resistant to standard treatments for their severe neurological and muscle autoimmune conditions each received a single IV infusion of the JY231 treatment.

In every patient, JY231 successfully generated CAR-T cells inside the body. The newly trained cells multiplied, peaking 11 days after injection, and traveled throughout the body.

The findings were published in the New England Journal of Medicine.

Reprogramming immune cells

CAR T-cell therapy is a promising therapeutic approach, but delivering it to patients is far from simple. Their immune cells must be extracted, shipped to a highly specialized laboratory for genetic modification and then returned to the patient, a process that can be both expensive and time-consuming.

Also, before patients can receive their reprogrammed cells, they must undergo lymphodepleting chemotherapy, in which drugs temporarily reduce the patient's existing immune cells to make room for the incoming cells. This step can be harsh and leave people with side effects including nausea, fatigue and headache.

Previous studies have suggested that viral vectors could overcome some of these limitations by achieving stable genomic integration with a single dose. To test this possibility, researchers conducted a small, single-group clinical trial involving adults with severe neurological or muscle autoimmune diseases who had not improved with standard treatments.

The study included seven patients with progressive multiple sclerosis (MS), three with myelin oligodendrocyte glycoprotein antibody–associated disease (MOGAD), in which antibodies attack a protein that protects nerves, three with generalized myasthenia gravis (gMG), a chronic autoimmune disorder that causes muscle weakness, and three with idiopathic inflammatory myopathies (IIM), a group of autoimmune diseases that cause inflammation in skeletal muscles.

Disease carrier gets a new role

The team engineered the harmless viral vector to deliver genetic instructions that reprogram a patient's own T cells to target CD19, a protein found on the B cells that cause autoimmune attacks. After giving participants a single intravenous (IV) drip of the experimental treatment, JY231, the researchers took regular blood, bone marrow and spinal fluid samples to monitor how the treatment worked at the molecular level.

The treatment rapidly wiped out the patients' B cells, which produce antibodies that fight foreign entities, with B-cell levels in the blood falling temporarily as a result. More than two months after the infusion, B cells began to return, but they were largely newly generated cells. The returning B cells were completely different from those present before treatment, suggesting that the therapy had essentially reset the immune system.

The treatment was highly accurate, with more than 99% of the reprogrammed cells successfully turning into the correct disease-fighting cells. Six months after treatment, patients in all four disease categories showed improvements in both symptoms and underlying biological markers.

New cells bring better outcomes

The seven MS patients experienced reduced physical disability, better physical and cognitive function, and significantly less fatigue. The three patients with gMG saw a clear decrease in the self-attacking antibodies targeting their nervous system. The MOGAD patients saw a clear decrease in self-attacking antibodies targeting their nervous system, and IIM patients experienced improved muscle strength.

None of the patients experienced the nerve-related side effects sometimes seen with this kind of therapy, a reassuring early sign of safety. A mild immune reaction called cytokine release syndrome did show up in about 69% of the patients after infusion. This happens when the immune system releases a flood of signaling proteins known as cytokines. However, these reactions were short-lived, fading completely within two weeks.

• Copy-number dynamics and distribution of CAR+ cells. Credit: New England Journal of Medicine (2026). DOI: 10.1056/nejmc2603114
• Clinical outcome measures after treatment. Credit: New England Journal of Medicine (2026). DOI: 10.1056/nejmc2603114

The researchers see these results as early proof of concept for treating hard-to-treat autoimmune diseases of the nervous system, but larger, randomized trials with longer follow-up are needed to confirm their long-term applicability and safety. If approved for clinical use, this approach could offer a new lifeline to millions of people living with autoimmune conditions who have run out of effective treatment options.

Written for you by our author Sanjukta Mondal, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

Publication details

Yu-Hang Cheng et al, Lentiviral In Vivo CD19 CAR T-Cell Therapy in Neurologic Autoimmune Disorders, New England Journal of Medicine (2026). DOI: 10.1056/nejmc2603114

Journal information: New England Journal of Medicine

Key medical concepts

Chimeric Antigen Receptor T-cellsAntigens, CD19B-LymphocytesMultiple Sclerosis, Chronic Progressive

Clinical categories

NeurologyAllergy and immunology Who's behind this story?

Sanjukta Mondal

Master's in Chemistry. Freelance science journalist and communicator. Published in Chemistry World, BioSpace, and The Hindu. Full profile →

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries. Full profile →

Robert Egan

Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →

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