CAR T immunotherapies are one of the hottest topics of research — and investment — in the world of medicine today. The emerging treatments have had shocking success in the past few years, even curing patients with aggressive, terminal cancer.

But so far, that success has largely been against blood cancers, notably leukemia and lymphoma. Bringing CAR T immunotherapies into solid tumors is the next frontier of the technology, and a new approach from the Fred Hutchinson Cancer Research Center may help it along the way.

In a recent study, Fred Hutch researchers used tiny, biodegradable nanoparticles to deliver two drugs directly into solid tumors. The drugs worked together to shut down the tumors’ defense mechanisms and rally the immune system. That opens the door for CAR T treatments, which are made up of genetically modified immune cells, to come in and attack the cancer cells.

The finding is important because it could help target CAR T treatments directly at tumors instead of sending them coursing throughout a patient’s body, which leads to potentially dangerous side effects. The research was published on the cover of the July issue of the journal Cancer Research.

While the study did not use human patients, the researchers said they successfully created a two-week window where tumors would be highly susceptible to CAR T cell treatments. The study lead, Fred Hutch researcher Dr. Matthias Stephan, said doctors “could use these nanoparticles to precondition the patient, and precondition the tumor, so that [the] T cells work much better.”

Stephan’s team is also experimenting with the same nanoparticle technology as a way to make CAR T therapies easier to make and administer, envisioning them as a replacement for chemotherapy as the front-line treatment for cancer.

The new research was supported by a grant from the National Institutes of Health and private support from the family of Amazon and Blue Origin CEO Jeff Bezos, which has become a prominent supporter of immunotherapy work at Fred Hutch over the past five years.