Table III.

Biological Activity of V13K Analogs Against Pseudomonas aeruginosa Strains

				Hemolytic Activity		Antimicrobial Activity								Therapeutic Indexa
						MIC (μg/ml)d
Peptide Name	Number of Positively Charged Residues	Number of Negatively Charged Residues	Net Charge	MHC (μg/ml)b	Foldc	PAO 1	PAK	CP 204	PA 14	WR 5	M 2	GMg	Folde	MHC/MIC	Foldf
V681	6	0	+6	7.8	0.03	15.6	31.3	15.6	62.5	62.5	15.6	27.8	1.8	0.3	0.06
−5	1	6	−5	>1000.0	8.0	>500.0	>500.0	>500.0	>500.0	>500.0	>500.0	1000.0	0.05	2.0	0.4
+1	7	6	+1	>1000.0	8.0	>500.0	>500.0	>500.0	>500.0	>500.0	>500.0	1000.0	0.05	2.0	0.4
+4S	4	0	+4	125.0	0.5	>500.0	>500.0	>500.0	>500.0	>500.0	>500.0	1000.0	0.05	0.1	0.02
+4E	7	3	+4	250.0	1.0	500.0	250.0	250.0	125.0	250.0	250.0	250.0	0.2	1.0	0.2
V13K	7	0	+7	250.0	1.0	31.3	125.0	7.8	62.5	250.0	31.3	49.6	1.0	5.0	1.0
+8	8	0	+8	250.0	1.0	31.3	62.5	7.8	31.3	62.5	31.3	31.3	1.6	8.0	1.6
+9	9	0	+9	<7.8	0.02	7.8	31.3	15.6	15.6	62.5	31.3	22.1	2.2	0.2	0.04
+10	10	0	+10	<7.8	0.02	15.6	15.6	7.8	15.6	31.3	31.3	17.5	2.8	0.2	0.04

^aTherapeutic index is the ratio of the MHC value (μg/ml) over the geometric mean MIC value (μg/ml). Large values indicate greater antimicrobial specificity.

^bMHC is the maximal peptide concentration that produces no hemolysis of human red blood cells after 18 h in the standard microtiter dilution method. When no detectable hemolytic activity was observed at 1000 μg/ml, a value of 2000 μg/ml was used for calculation of the therapeutic index and fold improvement. When hemolytic activity was still observed at 7.8 μg/ml, a value of 3.9 μg/ml was used for calculation of the therapeutic index and fold improvement.

^cThe fold improvement in hemolytic activity compared to that of lead compound, V13K.

^dMIC is minimal inhibitory concentration that inhibited growth of six P. aeruginosa strains in brain heart infusion (BHI) medium at 37°C after 24 h. MIC is given based on three sets of determinations. When no detectable antimicrobial activity was observed at 500 μg/ml, a value of 1000 μg/ml was used for calculation of the therapeutic index and fold improvement. The relative susceptibilities of P. aeruginosa strains to ciprofloxacin, with the number 1 denoting the most susceptible strain, are as follows: PAOl, 4; WR5, 1; PAK, 4; PA14, 8; M2, 8; CP204, 64.

^eThe fold improvement in antimicrobial activity (geometric mean data) compared to that of lead compound, V13K.

^fThe fold improvement in therapeutic index compared to that of lead compound, V13K.

^gGM, geometric mean of the MICs for the six P. aeruginosa clinical isolates.