Off-target messenger RNAs with partial seed-region complementarity (Seed-mediated off-targets)

Off-target messenger RNAs with partial seed-region complementarity represent a collective group of unintended transcripts that are downregulated by RNA interference (RNAi) therapeutics. This phenomenon occurs when the seed region of a therapeutic small interfering RNA (siRNA)—typically nucleotides 2 through 8 of the guide strand—binds to the 3' untranslated region (UTR) of non-target mRNAs with high complementarity (Jackson et al., 2003). Because the seed sequence is short, a single siRNA can potentially interact with hundreds of different transcripts, mimicking the natural regulatory mechanism of microRNAs (miRNAs) (Birmingham et al., 2006). These interactions often lead to unintended gene silencing, which can manifest as cellular toxicity or adverse clinical effects, particularly in the liver where many RNAi drugs are sequestered (Janas et al., 2018). To minimize these risks, drug developers employ chemical modifications, such as 2'-O-methyl substitutions at position 2 of the guide strand, to destabilize off-target binding while maintaining on-target potency (Burchard et al., 2009). Understanding and predicting these off-target profiles is a critical component of the safety assessment for any oligonucleotide-based drug candidate.

Other names

miRNA-like off-targetsSeed-based off-targetssiRNA off-target effectsSeed-region-mediated off-target effectsUnintended mRNA transcripts

Drugs such as siRNAs or miRNAs utilize the RNA-induced silencing complex (RISC) to bind to these unintended mRNAs via partial complementarity, primarily involving the seed region (nucleotides 2-8), resulting in transcript degradation or translational inhibition (Jackson et al., 2003; Birmingham et al., 2006).