In an important step toward more effective gene therapies for brain diseases, researchers from the Broad Institute of MIT and Harvard have engineered a gene-delivery vehicle that uses a human protein to efficiently cross the blood-brain barrier and deliver a disease-relevant gene to the brain in mice expressing the human protein. Because the vehicle binds to a well-studied protein in the blood-brain barrier, the scientists say it has a good chance at working in patients.

Gene therapy could potentially treat a range of severe genetic brain disorders, which currently have no cures and few treatment options. But FDA-approved forms of the most commonly used vehicle for packaging and delivering these therapies to target cells, adeno-associated viruses (AAVs), aren’t able to efficiently cross the blood-brain barrier at high levels and deliver therapeutic cargo. The enormous challenge of getting therapies past this barrier — a highly selective membrane separating the blood from the brain — has stymied the development of safer and more effective gene therapies for brain diseases for decades. 

Now researchers in the lab of Ben Deverman, an institute scientist and senior director of vector engineering at the Broad, have engineered the first published AAV that targets a human protein to reach the brain in humanized mice. The AAV binds to the human transferrin receptor, which is highly expressed in the blood-brain barrier in humans. In a new study published today in Science, the team showed that their AAV, when injected into the bloodstream in mice expressing a humanized transferrin receptor, crossed into the brain at much higher levels than the AAV that is used in an FDA-approved gene therapy for the central nervous system, AAV9. It also reached a large fraction of important types of brain cells, including neurons and astrocytes. The researchers then showed that their AAV could deliver copies of the GBA1 gene, which has been linked to Gaucher’s disease, Lewy body dementia, and Parkinson’s disease, to a large fraction of cells throughout the brain. 

The scientists add that their new AAV could be a better option for treating neurodevelopmental disorders caused by mutations in a single gene such as Rett syndrome or SHANK3 deficiency; lysosomal storage diseases like GBA1 deficiency; and neurodegenerative diseases such as Huntington’s disease, prion disease, Friedreich’s ataxia, and single-gene forms of ALS and Parkinson’s disease.

“Since we came to the Broad we’ve been focused on the mission of enabling gene therapies for the central nervous system,” said Deverman, senior author on the study. “If this AAV does what we think it will in humans based on our mouse studies, it will be so much more effective than current options.” 

“These AAVs have the potential to change a lot of patients’ lives,” said Ken Chan, a co-first author on the paper and group leader from Deverman’s group who has been working on solving gene delivery to the central nervous system for nearly a decade.

Source: https://www.broadinstitute.org/news/new-gene-delivery-vehicle-shows-promise-human-brain-gene-therapy