Benzinga | Sep 2, 2021 04:09PM EDT

Caribou Biosciences Announces Publication Of Data Demonstrating High Specificity Genome Editing With Its Proprietary chRDNA Technology

Caribou Biosciences, Inc. (NASDAQ:CRBU), a leading clinical-stage CRISPR genome-editing biopharmaceutical company, announced today the publication of data demonstrating that its proprietary CRISPR hybrid RNA-DNA (chRDNA) guide technology provides significantly improved specificity compared to all-RNA guides, thereby enabling high levels of intended genomic edits in cells while eliminating or minimizing inadvertent off-target events. Higher specificity is a key advantage in the development of therapeutics and of critical importance in therapies that contain multiple genome edits.

The data, which provide a mechanistic framework to elucidate the specificity of chRDNA guides, were published in an article entitled, "Conformational control of Cas9 by CRISPR hybrid RNA-DNA guides mitigates off-target activity in T cells," in the journal Molecular Cell.

"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., Caribou's 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., Caribou's 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."

The studies in the Molecular Cell paper were part of a collaboration between Caribou and the laboratory of Martin Jinek, Ph.D., at the University of Zurich, Switzerland. Dr. Jinek is a co-founder of Caribou and a leader in the field of CRISPR.

The Molecular Cell paper describes studies comparing the editing activity and specificity of Cas9 programed with either chRDNA or all-RNA guides at multiple independent genomic sites in human primary T cells. The data demonstrate that chRDNA guides enable highly specific Cas9-mediated editing, with little to no perturbation of on-target efficiency, while the all-RNA guides give rise to multiple unintended off-target editing events across the genome. The study also demonstrates that the number and location of DNA nucleotides in a chRDNA design can be tuned for each intended target site to allow for the maximal level of discrimination between on- and off-target sites. Structural analysis of target-bound Cas9-chRDNA complexes revealed that chRDNAs result in an altered geometry of the chRDNA and target DNA interface, and this alteration is accompanied by structural rearrangements of the Cas9 protein. These changes disfavor off-target DNA binding and modulate Cas9 cleavage activity to inhibit editing at off-target sites. The publication can be accessed here.

(Donohoue, Pacesa, et al., September 2, 2021, Molecular Cell 81(17), 3637-3649.)