BAX and infection: The combined assay optimization data allowed us to define standard conditions for the in vitro biopotency assay, where HepG2 cells (2.5 × 105 cells/mL or 6.25 × 104 cells/well) are pretreated with 2 mM HU prior to infection with BAX 335 in FreeStyle F17 medium, followed by an incubation period of 4 days.