Table 1.

IC₅₀ values of EPI-X4 determined in a 12G5-competition assay for CXCR4 mutants.

CXCR4 mutation	IC50 ± SEM (µM)	Fold change	Hill slopea	Interaction with EPI-X4b	Agreementc
wt	6.99 ± 2.63		−1.67 ± 0.50	-
L41A	131.83 ± 61.64	19	−1.02 ± 0.16	V2 sidechain, hydrophobic	yes
D97E	129.08 ± 49.34	18	−0.96 ± 0.11	L1 N-terminal, salt bridge	yes
D97S	784.78 ± 214.89	112	Nd	L1 N-terminal, salt bridge	yes
D97T	>1000	-	Nd	L1 N-terminal, salt bridge	yes
D97N	>1000	-	Nd	L1 N-terminal, salt bridge	yes
D97Q	>1000	-	Nd	L1 N-terminal, salt bridge	yes
V112A	10.96 ± 1.98	1.6	Nd	L1 sidechain, hydrophobic	yes
V112L	41.12 ± 17.33	6	−1.03 ± 0.14	L1 sidechain, hydrophobic	yes
D187E	8.52 ± 2.84	1.2	−1.25 ± 0.13	T5 sidechain, H bonds	yes
D262A	5.21 ± 1.67	0.7	−1.05 ± 0.04	K7 sidechain, salt bridge	no
E277A	8.91 ± 1.43	1.3	−1.21 ± 0.28	T5 sidechain, H bonds	yes
D97E + V112A	18.01 ± 2.95	2.6	−1.20 ± 0.15	-	yes
D97E + V112L	222.74 ± 133.83	32	−1.07 ± 0.15	-	yes
V112A + L41A	78.04 ± 13.91	11	−1.28 ± 0.26		yes
D97E + V112A + L41A	48.44 ± 24.73	7	−0.93 ± 0.16		yes

^aHill slopes were determined in GraphPad Prism using nonlinear regression curve fit. P > 0.05 for all hill slopes compared to wt (one-way ANOVA with Dunnett’s post hoc test).

^bEPI-X4 residues interacting with wild-type residues of CXCR4 in the NTER-IN model.

^cAgreement between the NTER-IN model and the mutagenesis experiments.