TABLE 5.

Cytotoxicity of bispecific EGFR × c-MET ADC on tumor cell line A431 and keratinocytes

EC₅₀ values for A431 cells and IC₅₀ values for keratinocytes (NHEK.f-c.) were calculated by sigmoidal curve fitting using GraphPad Prism version 5 (GraphPad Software). *, estimated values only due to poor fitting results. ED₈₀ represents the ADC concentration at which 80% of cells are killed in A431 cells in comparison with untreated cells. TD₂₀ stands for the dose where cell viability is reduced by 20% in keratinocytes. Two definitions for an in vitro translational therapeutic index or therapeutic window were calculated: the difference of IC₅₀ and EC₅₀ as well as the ratio of TD₂₀ to ED₈₀. For the calculation of the therapeutic window, error propagation was used. For statistical analysis, comparison with cetuximab-vc-MMAE is given.

Antibody	A431				NHEK.f-c.				Therapeutic window
	EC50	ED80	Cell killing at 50 nm	n	IC50	TD20	Cell killing at 50 nm	n	IC50 − EC50	TD20/ED80
	nm	nm	%		nm	nm	%		nm
B10v5 × 225-H-vc-MMAE	0.4 ± 0.1a	2.1 ± 0.7a	93 ± 1.3	5	5.9 ± 2.9b	4 ± 1c	37 ± 12	5	5.6 ± 2.8	2 ± 0.06
B10v5 × 225-M-vc-MMAE	1.0 ± 0.3d	4.4 ± 1.0d	91 ± 0.4	3	>19*	25 ± 8d	30 ± 9	3	>28*	6 ± 0.5
B10 × 225-M-vc-MMAE	0.7 ± 0.2d	3.6 ± 0.9e	90 ± 0.5	3	>20*	19 ± 8d	27 ± 11	3	>18*	5 ± 0.9
Cetuximab-vc-MMAE	0.1 ± 0.04	0.7 ± 0.3	92 ± 1.4	5	1.0 ± 0.5	0.8 ± 0.5	34 ± 10	5	0.9 ± 0.5	1 ± 0.2

^a p < 0.05.

^b p < 0.01, unpaired t test.

^c Not significant.

^d p < 0.001.

^e p < 0.01 (all analysis of variance).