Table 3.

RSV strain A2 virus yield reduction assay by NIH351 in HEp-2 and MA-104 cells

Compound	HEp-2 cells		MA-104 cells
	EC50	EC90	EC50	EC90
NIH351	0.3  ± 0.1 μM	1  ± 0.25 μM	0.3  ± 0.01 μM	1  ± 0.04 μM
Ribavirin	30  ± 6 μM	90  ± 6 μM	25  ± 3 μM	53  ± 33 μM

Both compounds were added only once, immediately before virus absorption. Infection was with A2 RSV strain. EC₅₀ and EC₉₀, concentration required to reduce virus replication by 50 and 90%, respectively. The EC₅₀ was determined by CPE directly on the primary assay wells that also received the antiviral agent to be tested. The EC₉₀ was determined on the secondary HEp-2 culture wells, where the virus titers from the primary wells were determined.