Scientists are developing a new drug delivery system to treat genetic diseases

A research team led by scientists from Harvard and the Broad Institute has developed a new drug delivery system that uses non-DNA virus-like particles (eVLPs) to package and deliver therapeutic levels of DNA-editing proteins. genes to animal models of disease. The team used eVLPs to modify a gene in mice that is associated with high cholesterol and to partially restore vision in mice with a point mutation that causes genetic blindness.

Given that eVLPs allow safer in vivo delivery of gene editing agents than some methods used in the clinic, with comparable or higher efficiencies, this new platform is a promising technology for the delivery of therapeutic macromolecules in patients. live animals with minimized risk of off-target editing. or DNA integration.

In the article published in Cell, the researchers detail how they developed virus-like particles to provide base editors, proteins that make single-letter programmable changes in DNA and the CRISPR-Cas9 nuclease, a protein that cuts DNA at targeted sites in the genome. The authors identified factors that influence the efficiency of virus-like particle delivery and demonstrated that engineering virus-like particles can overcome multiple structural limits to their potency. The safe and efficient delivery of gene editing agents to cells of living humans and animals is a major challenge. The team’s eVLPs are the first virus-like particles to deliver therapeutic levels of basal editors to a variety of cell types in adult animals.

The delivery of therapeutic macromolecules into mammalian cells in animals and eventually in patients is one of the most important challenges in the life sciences. There is often a very steep drop between in vitro and in vivo delivery, so we made the decision early on that our new delivery technology should show good efficacy in animal models. »

David Liu, lead author of the paper, Thomas Dudley Cabot Professor of Natural Sciences and senior faculty member at the Broad Institute

This work was led by members of Liu’s lab, including postdoctoral fellow Samagya Banskota and graduate student Aditya Raguram, in collaboration with research teams led by Krzysztof Palczewski of the University of California, Irvine and Kiran Musunuru from the Perelman School of Medicine at the University of Pennsylvania.

This new delivery system finds a new use for virus-like particles and builds on the success of base editors, which the Liu lab developed in 2016 to rewrite individual DNA bases such as mutations that cause thousands of genetic diseases.

Virus-like particles, assemblies of viral proteins that can infect cells but lack viral genetic material, have long been studied as vehicles for drug delivery. Because they are able to carry molecular cargo and lack viral genetic material, they are able to exploit the efficiency and tissue targeting benefits of viral delivery without the drawbacks of using viruses real ones, which can insert their genetic material into the cell’s genome and potentially cause cancer. . However, existing VLP delivery strategies have had limited therapeutic efficacy in vivo.

To successfully deploy VLPs, the team identified delivery limitations and systematically designed VLP components to overcome bottlenecks related to packing, releasing, and tracking cargo. In doing so, they developed fourth-generation eVLPs that packed 16 times more protein cargo than previous designs and enabled an eight- to 26-fold increase in editing efficiency in cells and animals.

The team tested their optimized eVLP system to deliver baseline editors to the liver in mice, where they effectively edited a gene that can lower levels of “bad” cholesterol. A single injection of eVLP resulted in an average 63% change in the target gene and a 78% drop in its protein levels, significantly reducing the risk of coronary heart disease.

“The cholesterol target is particularly interesting because it’s not just for patients with a rare genetic disease,” Raguram said. “We hope this is an example of genome editing that can benefit a large population, as cholesterol levels impact the health of billions of people.”

The researchers also used a single injection of eVLP to correct the disease-causing point mutation in mice with a genetic retinal disorder. They effectively corrected the point mutation with less focused editing than other basic editing techniques, resulting in partial vision restoration.

The team also injected eVLPs directly into mouse brains and observed around 50% editing efficiency in cells exposed to eVLPs.

Going forward, Banskota is optimistic that eVLPs will be used quite easily by scientists due to the system’s relative simplicity and versatility.

“Because our system is relatively simple and easy to design, it allows other scientists to quickly adopt and scale up this technology,” Banskota said. “Beyond the transport of gene editors, eVLPs have the ability to transport other macromolecules with great therapeutic potential.”


Journal reference:

Bankota, S., et al. (2022) Virus-Like Particles Designed for Efficient In Vivo Delivery of Therapeutic Proteins. Cell.

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