Last year we worked alongside authors from Amgen and published data in support of refining the hERG testing strategy for silencing RNA (siRNA). In accordance with the ICH S7B guidelines, an in vitro assay targeting the hERG channel forms a crucial component of the integrated risk assessment for delayed ventricular repolarization. The function of hERG may be influenced by either direct (acute) mechanisms or indirect (chronic) mechanisms. While some approved oligonucleotide therapeutics have submitted hERG data to regulatory bodies, gathered using protocols akin to small-molecule testing (with an incubation time <20 min, indicative of acute effects), oligonucleotides operate via distinct mechanisms and timelines (notably indirect effects).