Off-target genomic DNA loci (KLKB1-targeting)

Off-target genomic DNA loci with partial complementarity to the KLKB1-targeting guide RNA are unintended sequences in the genome where a CRISPR-Cas9 complex may bind and induce double-strand breaks. These sites possess high sequence homology to the intended target site within the Kallikrein B1 (KLKB1) gene, which is targeted to reduce plasma prekallikrein levels in patients with hereditary angioedema (Long et al., NEJM, 2024). In therapies like NTLA-2002, the guide RNA is designed to be highly specific, but the Cas9 enzyme can occasionally tolerate mismatches, leading to cleavage at these off-target locations (Intellia Therapeutics, 2024). Such unintended modifications pose significant safety risks, including the potential for gene disruption, chromosomal translocations, or the activation of oncogenes. Consequently, these loci are not therapeutic targets but rather safety liabilities that must be rigorously screened using methods like GUIDE-seq or CIRCLE-seq (Tsai et al., Nature Biotechnology, 2015). Minimizing activity at these sites is essential for the clinical viability and regulatory approval of gene-editing medicines. The characterization of these loci is a critical component of the safety profile for any CRISPR-based intervention targeting the KLKB1 pathway.

Other names

Off-target sitesUnintended genomic modificationsCRISPR off-targetsNon-specific DNA binding sites

Unintended CRISPR-Cas9 mediated DNA cleavage and non-homologous end joining (NHEJ) at non-target genomic sites.