Although vaccines are of major importance in the battle against the Sars-CoV-2 virus responsible for COVID-19, issues including vaccine hesitancy, availability, virus evolution and incomplete vaccine effectiveness mean that effective treatments are also required.  There is currently no Sars-CoV-2 specific antiviral treatment, but a number of existing antiviral agents are under investigation for repurposing as Sars-CoV-2 treatments.  Amongst these are remdesivir and favipiravir (Wadaa-Allah et al, 2021) and the ribonucleoside analogue molnupiravir (also known as EIDD-1931; Sheahan et al, 2020) which is currently in human trials (NCT04405739 and NCT04405570).  Concerns have been raised about potential risks of arrhythmia, including drug-induced QT interval prolongation, in COVID-19 patients (e.g. Carpenter et al, 2020).  As the cardiac hERG potassium channel is a major culprit in drug-induced arrhythmia, the purpose of this investigation was to determine in silico the ability of remdesivir, favipiravir and molnupiravir to interact with known drug binding determinants in the hERG channel pore region.  Established computer models of the pore domain of hERG (Helliwell et al, 2018; Dickson et al, 2020) were employed and antiviral molecules were docked using GOLD v2020.1 and GOLD version 5.6.  The side chains of S6 domain aromatic residues (Y652 and F656) were unconstrained during docking simulations.  Rotamer sampling was maximally set to 300,000 generations. Remdesivir could be accommodated in the open state but not closed state channel models.  In open channel models, remdesivir could interact with F656, Y652 on the S6 domain and L622 and S624 residues near the channel selectivity filter.  Additionally, part of the remdesivir molecule could advance towards lateral side pockets and interact with the F577 S5 residue.  Favipiravir is a much smaller molecule and could be accommodated in both open and closed channel models and interact with known binding residues.  However, its small size meant that it made comparatively few simultaneous binding contacts in the open state and weak binding contacts in the closed state.  Molnupiravir is intermediate in size between favipiravir and remdesivir.  When docked to the open hERG structure it was able to make favourable interactions with the S6 aromatic residue Y652 and with residues under the selectivity filter (e.g. S624), but was unable simultaneously to access lateral side pockets and the F577 residue.  Molnupiravir could be accommodated in the central cavity of the closed hERG model, however the fit was relatively poor with a potential to interact with residues under the selectivity filter and contact both the S6 aromatic residues: Y652 and F656.  The results of this in silico study indicate that all 3 antiviral agents studied can interact with hERG channels; the small size of favipiravir makes it likely to have reduced hERG liability.  These in silico findings provide a rational basis for further in vitro and in vivo investigations in order to compare the ability of these agents to produce inhibition of hERG channel current and delay ventricular repolarization. Acknowledgment The authors acknowledge research funding from the British Heart Foundation (PG/17/77/33125, PG/17/89/33414 and PG/20/10252).