Off-target effects of oligonucleotides and approaches of preclinical assessments

Oligonucleotide-based therapies, such as antisense oligonucleotides (ASOs), small interfering RNAs (siRNAs), represent a class of therapeutic agents that specifically target gene transcription or translation mechanisms through sequence specificity. These pharmaceuticals exhibit significant promise in the treatment of genetic disorders, including spinal muscular atrophy, as well as malignancies, viral infections, and metabolic diseases. Nonetheless, unintended toxicity continues to pose a considerable challenge and remain a critical safety concern in the development of oligonucleotide therapeutics (ONTs). Off-target toxicity may be caused by hybridization to sequences that are similar but not identical to the target, hybridization-independent sequence related, or sequence- and hybridization-independent effects. The effects may result in diminished transcript levels, decreased translation rates, or anomalous splicing, employing same molecular pathways and protein machinery as the desired on-target effects. Currently, there exists no established methodology for the systematic identification and evaluation of off-target toxicity, which may hinder the optimization of safety approaches. This review delineates significant nonclinical toxicities and clinical adverse effects by summarizing and analyzing approved oligonucleotides with their off-target assays, encompassing the limitations of nonclinical off-target effects and the potential off-target mechanisms. Plus, it discusses and emphasizes the factors that lead to the off target of ONTs, systematically offers approaches and workflows of preclinical assessments to enhance the transfer value of oligonucleotide therapies from nonclinical to clinical trials by managing unavoidable off-target effects.