Mix and go for cell therapy?

SEATTLE—Researchers at the Fred Hutchinson Cancer Research Center have designed a new biomedical tool that uses nanoparticles to deliver transient gene changes to targeted cells, in what they say could make therapies for cancer, diabetes, HIV and other diseases faster and cheaper to develop, as well as more customizable. This new tool, which has been tested only in preclinical models thus far, was described in a paper published August 30 in Nature Communications.

“Our goal is to streamline the manufacture of cell-based therapies,” said lead author Dr. Matthias Stephan, a faculty member in the Fred Hutch Clinical Research Division and an expert in developing biomaterials. “In this study, we created a product where you just add it to cultured cells and that’s it—no additional manufacturing steps.”

The nanoparticle delivery system was designed specifically to extend the therapeutic potential of messenger RNA (mRNA), and the researchers took that approach of focusing on specific cell types: T cells of the immune system and blood stem cells.

The mRNA is delivered directly to the cells, triggering short-term gene expression in what they refer to as “hit-and-run” genetic programming, because, as Fred Hutch puts it, “the transient effect of mRNA does not change the DNA, but it is enough to make a permanent impact on the cells’ therapeutic potential.”

The basic process:

• Nanoparticles carried a gene-editing tool to T cells of the immune system that snipped out their natural T cell receptors, and then was paired with genes encoding a “chimeric antigen receptor” or CAR, a synthetic molecule designed to attack cancer.

• Targeted to blood stem cells, nanoparticles were equipped with mRNA that enabled the stem cells to multiply and replace blood cancer cells with healthy cells when used in bone marrow transplants.

• Nanoparticles targeted to CAR-T cells and containing foxo1 mRNA, which signals the anti-cancer T cells to develop into a type of “memory” cell that is more aggressive, destroys tumor cells more effectively and maintains anti-tumor activity longer.

One of the problems with mRNA therapy is that the large messenger molecule degrades quickly before it can have an effect, and the body’s immune system recognizes it as essentially a foreign invader and attacks it.

“We developed a nanocarrier that binds and condenses synthetic mRNA and protects it from degradation,” Stephan said, explaining his team’s workaround. The researchers surrounded the nanoparticle with a negatively charged envelope with a targeting ligand attached to the surface so that the particle selectively homes in on and binds to a particular cell type.

The cells swallow up the tiny carrier, which can be loaded with different types of manmade mRNA. “If you know from the scientific literature that a signaling pathway works in synergy, you could co-deliver mRNA in a single nanoparticle,” Stephan explained. “Every cell that takes up the nanoparticle can express both.”

The approach involves mixing the freeze-dried nanoparticles with water and a sample of cells. Within four hours, cells start showing signs that the editing has taken effect. Boosters can be given if needed. Made from a dissolving biomaterial, the nanoparticles are removed from the body like other cell waste.

“Just add water to our freeze-dried product,” Stephan said.

Since it’s built on existing technologies and doesn’t require knowledge of nanotechnology, Stephan sees this as an off-the-shelf way for cell-therapy engineers to develop new approaches to treating a variety of diseases. The approach could replace labor-intensive electroporation, a multistep cell-manufacturing technique that requires specialized equipment and clean rooms. All the handling ends up destroying many of the cells, which limits the amount that can be used in treatments for patients.