TABLE 3.

Activity of benzimidazole nucleoside 1311 against HCMV strains resistant to GCV, CDV, and PFA

Compound	IC50 (μM) against the following virusesa:
	17517	48041	AD169	4760 Rec Pol A	1117 3-1-2
1311	0.57 ± 0.23	0.82 ± 0.35	0.82 ± 0.10	0.87 ± 0.07	0.96 ± 0.07
GCV	3.2 ± 2.6	27 ± 8*b	11.8 ± 3.9	14.3 ± 1.5	48.3 ± 5.5*
BDCRB	0.46 ± 0.24	0.64 ± 0.05	0.58 ± 0.05	0.50 ± 0.11	0.53 ± 0.04
PFA	NDc	ND	50 ± 13	190 ± 10*	52 ± 11
CDV	ND	ND	0.44 ± 0.04	0.40 ± 0.07	2.27 ± 0.67*

^aInhibition of HCMV plaque formation was measured by using at least six drug concentrations ranging from 100 to 0.05 μM. Data are presented as the means±SDs of IC₅₀s determined in at least triplicate. HCMV strains 17517 (GCV sensitive) and 48041 (GCV resistant) are a matched pair of clinical isolates. Strain 48041 is resistant to GCV due to a mutation (L595S) in UL97 (K. K. Biron, personal communication). HCMV strains 4760 Rec Pol A (PFA resistant) and 1117 3-1-2 (CDV resistant) were derived from AD169 (wild type) and manifest their resistance to PFA or GCV and CDV due to mutations in the UL54 viral DNA polymerase gene (3).

^b*, P < 0.005 as determined by the Student's t test function of Microsoft Excel.

^cND, not determined.