Caribou Releases Data Proving High Specificity Genome Editing

Caribous patented chRDNA technology for therapeutic purposes has a mechanistic framework, according to data published in Molecular Cell.

FREMONT, CA: Caribou Biosciences has released data proving that its unique CRISPR hybrid RNA-DNA (chRDNA) guide technology outperforms all-RNA guides in terms of specificity, allowing for high levels of desired genomic alterations in cells while preventing or decreasing unintended off-target events. Higher specificity is a significant benefit in the development of medicines, especially in regimens that include several genome modifications.

The research published in Molecular Cell resulted from a cooperation between Caribou and Martin Jinek's team at the University of Zurich in Switzerland. Dr. Jinek is a co-founder of Caribou and a pioneer in CRISPR research.

In the work published in Molecular Cell, researchers compared the editing activity and specificity of Cas9 programmed with either chRDNA or all-RNA guides at different genomic locations in human primary T cells. The findings show that chRDNA guides allow very targeted Cas9-mediated editing with little to no off-target effects. In contrast, all-RNA guides cause many undesired off-target editing events across the genome. The research also shows that the quantity and placement of DNA nucleotides in a chRDNA design can be adjusted for each desired target site to achieve the best possible discrimination between on- and off-target locations. 

The chRDNAs cause a changed geometry of the chRDNA and target DNA interface, accompanied by structural rearrangements of the Cas9 protein, according to structural studies of target-bound Cas9-chRDNA complexes. Off-target DNA binding is discouraged, and Cas9 cleavage activity is modulated to prevent editing at off-target locations.

“Caribou is currently developing unique allogeneic CAR-T cell therapies with multiple genome edits designed to enhance their persistence in patients,” said Steve Kanner, Ph.D., Caribous chief scientific officer. “By altering the position and number of DNA residues in our chRDNA guides, we readily achieve optimal on-target editing and minimize unintended off-target edits that may be problematic in therapeutic applications.”

“These data demonstrate that our chRDNA editing platform provides an efficient and highly customizable approach to develop sophisticated allogeneic CAR-T cells for the treatment of hematologic malignancies,” said Rachel Haurwitz, Ph.D., Caribous president, and chief executive officer. “The first of Caribou’s multiplex-edited product candidates, CB-010, is being evaluated in an ongoing Phase 1 clinical trial in patients with relapsed or refractory B cell non-Hodgkin lymphoma and we look forward to initial clinical data in 2022.”