Table 3.

Selection studies using PSI-7977 in GT 1b, 1a, and JFH-1 2a replicons^a

Replicon cell	Day of selection	PSI-7977 concnb (μM)	Fold change in EC50	NS5B amino acid substitution(s)
GT 1b	36	0.6	3.4	None
	56	0.9	5.0	S282T
GT 1a	86	0.5	1.1	None
	139	2.0	6.1	S282T, I434 M
GT 2a	105	1.2	5.9	T179A, M289L, I293L
	137	3.0	21.9	T179A, S282T, M289L, I293L
	149	3.0	13.5	T179A, S282T, M289L, I293L, M434T, H479P

^aLunet cells stably expressing GT 1b, 1a, or JFH-1 2a replicons were cultured in the presence of increasing concentrations of PSI-7977. The starting concentration for PSI-7977 was 0.3 μM in GT 1b replicon cells and 0.05 μM in GT 1a and JFH-1 2a replicon cells. Susceptibility studies and NS5B sequencing were performed at various days of selection to monitor for resistance. EC₅₀ fold change (single-point determinations performed in duplicate on the particular day of selection) was determined by normalizing the EC₅₀ of the PSI-7977-selected cells with that of the no-drug control cells.

^bConcentrations of PSI-7977 in which replicons cells were cultured and when the mutation(s) was identified.