PNP and influenza: Ulodesine is an investigational PNPI used to treat hyperuricemia and gout.45 8-aminoinosine is reported to exert diuretic and natriuretic activity by inhibiting purine nucleoside phosphorylase.46 All the three PNPI showed marked inhibitory effect on the viral copy number in the supernatant of H1N1-infected MDCK cells, indicating the anti-influenza potential of PNPIs (Fig. 8a).