Three-component nanoparticles reprogram T cells inside the body to kill B-cell cancers
Johns Hopkins Medicine
CAR-T cell therapy has transformed treatment for certain blood cancers. But it comes with a brutal bottleneck: doctors must draw a patient's blood, ship T cells to a specialized lab, engineer them to recognize cancer, grow them for weeks, and infuse them back. The process can cost hundreds of thousands of dollars and takes time that some patients do not have.
What if the engineering could happen inside the patient's own body?
A team at Johns Hopkins Medicine has taken a significant step toward that goal. In a study published March 11, 2026, in Science Advances, biomedical engineer Jordan Green and immunologist Jonathan Schneck describe biodegradable nanoparticles that travel through the bloodstream, find T cells, activate them, enter them, and deliver mRNA instructions to build cancer-targeting receptors on their surface. In healthy mice, a single injection depleted 95% of target B cells in circulating blood within 24 hours.
A three-stage rocket for inner space
Green compares the nanoparticles to a multistage rocket. Each component handles a different phase of the mission. The outer surface carries two antibody molecules, antiCD3 and antiCD28, which help the particle find and latch onto T cells. Once attached, these signals stimulate the T cell to activate and multiply. Then the particle passes through the cell membrane, biodegrades, and releases its cargo: mRNA encoding a receptor that directs the T cell to seek out and destroy B cells.
The design uses only three components, compared to five or more in lipid-based nanoparticle systems developed by other groups. The polymer backbone is built from ester units that break down in water, making the particles fully biodegradable.
Getting past the immune system's bouncers
Engineering nanoparticles to reach T cells throughout the body is harder than delivering them to a localized site like the eye. T cells evolved to resist foreign material. If they easily internalized viral particles, infections like HIV would hijack the entire immune system.
The Johns Hopkins team found that their particles match the performance of commercial magnetic beads used in laboratories to stimulate T cells, but then go further by actually entering the cells and reprogramming them from the inside. In previous work, the group showed that about 10% of their nanoparticles escape the cell's degradation compartments to deliver intact genetic cargo, compared to 1-2% for other nanoparticle designs.
In the current study, the particles degraded and released their mRNA contents within a few hours in mice. The mRNA instructed T cells to express receptors targeting B cells, which are the source of diseases including lupus, leukemia, and lymphoma.
95% depletion in blood, 50% in the spleen
Twenty-four hours after a single injection in healthy mice, 95% of target B cells were depleted from circulating blood and about 50% were destroyed in the spleen. After one week, B cells in the blood had returned to roughly 50% of their original levels, suggesting the effect is potent but temporary, which could be an advantage for conditions requiring short-term immune modulation rather than permanent cell elimination.
Still far from the clinic
This is a proof-of-principle study in healthy mice. The nanoparticles have not been tested in disease models, and the gap between depleting B cells in a healthy mouse and treating cancer or autoimmune disease in a human patient is substantial.
The temporary nature of the effect, while potentially useful, also means repeat dosing may be necessary. Long-term safety data do not exist. The specificity of the targeting, how well the particles avoid reprogramming the wrong T cells or causing off-target immune activation, needs thorough evaluation.
Manufacturing scalability, while theoretically simpler than CAR-T production, has not been demonstrated at clinical scale. And the regulatory path for an off-the-shelf injectable that reprograms immune cells in vivo is largely uncharted.
The team, which recently joined a collaboration with biotechnology company ImmunoVec on a $40 million grant from the Advanced Research Projects Agency for Health, plans to refine the nanoparticles for better targeting of diseased B cells and adjustable levels of T-cell stimulation.
The bigger bet
The appeal of in-body immune cell engineering extends well beyond cancer. If nanoparticles can reliably reprogram T cells without removing them from the patient, the same platform could theoretically be adapted for autoimmune diseases, transplant rejection, or infectious diseases. The key word is "if." Five years of development led to this mouse study. The path to human patients will require many more.