Peptidomimetic furin inhibitor MI-701 in combination with oseltamivir and ribavirin efficiently blocks propagation of highly pathogenic avian influenza viruses and delays high level oseltamivir resistance in MDCK cells

•Blockage of HA cleavage by the furin inhibitor MI-701 suppresses replication of highly pathogenic avian influenza viruses.•Suppression of virus replication is enhanced when MI-701 is combined with oseltamivir and ribavirin.•MI-701 resistant virus mutants have not been observed.•Emergence of high-level oseltamivir resistant virus mutants is delayed in presence of MI-701.