The 2'-endo conformation of arabinose-CTP and arabinose-UTP inhibit viral polymerases by inducing long pauses.

Key to supporting human health in the face of evolving viruses is the development of novel antiviral drug scaffolds with the potential for broad inhibition of viral families. Nucleoside analogs are a key class of drugs that have demonstrated potential for the inhibition of several viral species. Here, we evaluate arabinose nucleotides (ara-NTP) as inhibitors of the SARS-CoV-2 and poliovirus polymerases using biochemistry, biophysics and structural biology. Ara-NTPs compete poorly with their natural counterparts for incorporation into RNA by viral polymerases. However, upon incorporation, ara-NMPs induce long polymerase pausing in both SARS-CoV-2 and poliovirus polymerase RNA elongation. Our studies suggest that subsequent nucleotide incorporation is inhibited at the catalytic step due to the 2'-endo sugar pucker of the incorporated ara-NMP.