In vitro antiviral activity of the 6-substituted 2-(3',4'-dichlorophenoxy)-2H-pyrano[2,3-b]pyridines MDL 20,610, MDL 20,646, and MDL 20,957.

The 6-substituted 2-(3',4'-dichlorophenoxy)-2H-pyrano[2,3-b]pyridines MDL 20,610 (6-SO2CH3), MDL 20,646 (6-Br), and MDL 20,957 (6-Cl) are potent antirhinovirus compounds with median plaque 50% inhibitory concentrations (IC1/2s) of 0.03, 0.006, and 0.006 micrograms/ml, respectively, against the 32 serotypes evaluated. The 6-halogenated analogs produced 99% reductions in progeny virion yields at concentrations as low as 0.004 micrograms/ml. However, these analogs perturbated HeLa cell metabolism at lower concentrations (at or above 5 micrograms/ml) than did the 6-methylsulfonyl analog (at or above 20 micrograms/ml). Compound MDL 20,610 was also active against human, simian, and bovine rotaviruses (cytopathic effect IC1/2s of 0.8 to 1.5 micrograms/ml) and possessed variable enterovirus and paramyxovirus activity.