Cyclo(-Met-Pro) is a cyclic dipeptide consisting of the amino acids methionine and proline. Cyclo(-Met-Pro) exhibits weak inhibitory activity against the influenza A virus (H3N2) (5 mM, 2.1% inhibition), while cis-cyclo(Leu-Pro) and cis-cyclo(Phe-Pro) shows significant antiviral activity[1].