TABLE 1.

Serial passages and colony formation of replicon cells in increasing concentrations of AG-021541^a

Passage nos.	AG-21541 concn (μM)	EC90 factor	Concn for colony formation (EC90 factor)	No. of days to obtain colonies
1-3	3	0.2	ND
4-6	6	0.4	ND
7-9	12	0.8	1.6	41
10-12	24	1.6	3.2	50
13-15	48	3.2	6.4	59
16-18	96	6.4	12.8	No colony
19-21	192	12.8	ND

^aThe replicon cells were cultured in the starting concentration of 0.2× EC₉₀ of AG-021541. The cells were cultured until they reached 90 to 100% confluence (an average of 3 days), and the compound concentration was doubled after every three passages until cytotoxicity became apparent at 12.8× EC₉₀. Cells grown at 0.8× EC₉₀, 1.6× EC₉₀, and 3.2× EC₉₀ of AG-021541 were subjected to colony formation at 1.6× EC₉₀, 3.2× EC₉₀, and 6.4× EC₉₀, respectively. ND, not done.