Table 1.

Key parameters used for comparing in vitro data

Term	Definition
EC50	Effective concentration needed to achieve 50% of maximal response (50% viral inhibition)
IC50	Inhibitory concentration needed to inhibit a process by 50% (usually intended for antagonist drug potency, but often interchanged with EC50 when discussing antiviral therapy)
CC50	Cytotoxic concentration needed to cause death among 50% of host cells
SI	CC50/EC50; selectivity index to describe a given drug’s therapeutic window