Partially complementary off-target RNAs

Partially complementary off-target RNAs are unintended messenger RNA (mRNA) or non-coding RNA transcripts that share sequence homology with oligonucleotide-based therapeutics, such as small interfering RNAs (siRNAs) or antisense oligonucleotides (ASOs). These molecules are not therapeutic targets but rather 'anti-targets' that represent a significant safety liability in the development of nucleic acid drugs (Birmingham et al., 2006, Nature Methods). When a drug binds to these off-targets—often mediated by the 5' seed region of an siRNA—it can trigger unintended gene silencing, degradation, or translational inhibition, potentially leading to cellular toxicity or adverse clinical events (Setten et al., 2019, Nature Reviews Drug Discovery). This phenomenon is a primary driver of hepatotoxicity and other side effects observed in RNA-targeted platforms. To mitigate these risks, drug developers utilize advanced bioinformatic screening and chemical modifications, such as 2'-O-methyl or locked nucleic acids, to enhance specificity for the intended target and reduce affinity for partially complementary sequences (Janus et al., 2018, Nucleic Acids Research). Understanding the landscape of these off-target interactions is critical for ensuring the safety profile and therapeutic index of modern RNA-based medicines.

Other names

Off-target transcriptsUnintended RNA targetsSeed-mediated off-targetsNon-target mRNAsCross-reactive RNA species

Oligonucleotide drugs (siRNAs or ASOs) bind to unintended RNA transcripts via partial sequence complementarity, particularly through the 'seed region' (nucleotides 2-8), leading to RISC-mediated cleavage or translational repression (Jackson et al., 2003, Nature Biotechnology).