A new study published in the journal Science in June 2025, describes a method to generate Chimeric Antigen Receptor (CAR) T cells directly inside the body, potentially simplifying a complex cancer treatment. Researchers developed targeted lipid nanoparticles (tLNPs) that deliver messenger RNA (mRNA) to T cells, bypassing the need to engineer cells outside the body, as required in traditional CAR T cell therapy. This ex vivo process, used to treat certain blood cancers like leukemia, involves extracting T cells, modifying them in a lab, and reinfusing them, often taking weeks and requiring specialized facilities. The new approach aims to reduce time, cost, and infrastructure barriers.

The tLNPs, designed with a specialized lipid called L829, target CD5, a protein on T cells, and avoid uptake by the liver, a common issue with standard nanoparticles. The mRNA instructs T cells to produce CARs, enabling them to attack cancer or diseased cells without permanent genetic changes, a safety advantage over DNA-based methods. Tests in human blood samples from autoimmune disease patients showed the tLNPs could engineer T cells to eliminate B cells. In mice with human immune cells, a single dose depleted B cells within hours, lasting up to two weeks. Repeated doses in a leukemia mouse model nearly cleared tumors.

The findings indicate the method could work for cancer and autoimmune conditions, but human trials are needed to confirm safety and effectiveness. Challenges include ensuring precise targeting, avoiding immune reactions to the nanoparticles, and scaling production.

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