Table 2.

IC₅₀ Values (μM) and Cytotoxicity for the New-Generation Peptides

Peptide	Sequencea			IC50 (μM) YU2 (R5)b	TIc (μM)
	178	184	187
2C	CSSHFPYSQYQFWK			28±7d	>125–250
12–1	SSHFPYSQYQFWK			208±11	>500–1000
12–2	. . . . .F. . . . . . .			96.7±15	>500
12–3	. . . . .V. . . . . . .			ntf	>5
12–4	. . . . .W. . . . . . .			122±19	>500
12–5	. . . . . . . .R . . . .			2182±194	nt
12–6	. . . . . . . .T . . . .			1285±159	nt
12–7	. . . . . . . .V. . . .			753±398	nt
14–1	. . . . .F. .R. . . .			1170±134	>500–1000
14–2	. . . . .W. .R. . . .			726±31	>500–1000
14–3	. . . . .F. .T. . . .			611±69	nt
14–4	. . . . .W. .T. . . .			147±26	NDe
14–5	. . . . .F. .V. . . .			NAe	>500
14–6	. . . . .W. .V. . . .			NA	>200
16–3	C. . . . .W. . . . . . .			14.5±2.1	nt
16–4	C. . . . . . . .F . . . .			nt	>100
16–5	C. . . . .F . . F . . . .			nt	>50
16–6	C. . . . .F. .V. . . .			nt	>5
16–7	C. . . . .W. .V. . . .			nt	>75

^aAmino acid sequence numbered as in ECL2 of CCR5, Figure 1.

^bCCR5-tropic HIV strain. Neutralization assays were performed as described previously.⁹

^cToxicity index. Ratio of cytotoxicity to neutralization IC values.

^d50 Data from ref 5.

^ent, not tested due to weak HIV inhibitory activity or high cellular toxicity.

^fNA, not active at ≤500 μM.