Injected nanoparticles reprogram killer immune cells in mice

A single injection, in mice. That is what MIT engineers report. Their lipid nanoparticles carry mRNA, the molecular instructions a cell uses to build a protein, into the bloodstream, where they reach natural killer (NK) cells, the immune cells that destroy abnormal cells. Once inside, the NK cells start building a chimeric antigen receptor (CAR), a receptor that tells the cell which target to attack. The work is published in Nature Biotechnology under the title "In vivo engineering of CAR natural killer cells for immunotherapy using ligand-directed lipid nanoparticles".

The numbers come from mice. The lead formulations achieved up to ~80% NK cell transfection, meaning the share of cells that took up and expressed the new instructions, with minimal off-target effects. In healthy mice, CD19-targeted CAR NK cells completely depleted circulating B cells. In humanized mice, meaning mice carrying human immune components, treatment eradicated T-cell lymphoma. In a melanoma model, 3 of 5 mice reached complete remission. In a mouse model of autoimmune hepatitis, one injection eliminated autoreactive T cells and healed liver damage, according to phys.org's coverage of the work. The study's own summary adds that NKG2A-targeting nanoparticles relieved Qa-1b-mediated immunosuppression in solid tumors. Five mice per group is a small sample, and none of these results has yet been reported in people.

The context explains the caution. According to AZO Life Sciences, there are currently no FDA-approved CAR NK cell therapies, although many researchers are working on them. The approach is also nonviral, which the Nature Biotechnology abstract presents as its main difference from current methods of cell engineering. Nature Medicine, in an editorial titled "A reality check for autoimmune CAR T cells", describes the hope that CAR T therapies can reset the immune system and induce deep remission, and notes that recent trial pauses have renewed concerns about safety, patient selection and acceptable risk. Those concerns concern CAR T cells, not NK cells, but they frame how any in vivo approach will be judged.

What would change, and for whom? If the results hold in larger animals and in people, patients with autoimmune disorders caused by dysfunctional T cells, and patients with cancer, would be the first to benefit, since researchers hope engineered NK cells could treat both. The sources give no date for a first human study, no dose and no price, and they do not say when such a treatment could reach a clinic. For now, the change is a demonstrated principle in mice: a nanoparticle injected into the body can reprogram immune cells already inside it.