TABLE 1.

Neutralization potencies and apparent binding affinities of actoxumab and bezlotoxumab against purified toxins of different ribotypes

Strain	Actoxumab/TcdA		Bezlotoxumab/TcdB
	K′d (ng/ml)a	EC50 (ng/ml)b	K′d (ng/ml)	EC50 (ng/ml)
087c	3.1 ± 1.2	18	8.1 ± 2.8	5.2
001	3.1 ± 1.7	16	5.8 ± 0.9	4.5
002	4.1 ± 1.0	22	6.8 ± 1.3	4.5
014	5.3 ± 1.5	38	62.3 ± 0.5d	5.1
017	NAe	NA	4.4 ± 0.7	1.7
027	699 ± 70f	1,900	291 ± 11f	960
036	NA	NA	300 ± 197f	890
078	637 ± 633f	1,500	173 ± 111f	130
106	15.7 ± 1.9d	26	5.6 ± 1.9	2.0

^aK′_d values are means ± standard deviations of at least two separate determinations.

^bEC₅₀ values are from representative experiments.

^cStrain 087 is VPI 10463.

^dP < 0.05, compared to ribotype 087.

^eNA, not applicable; ribotypes 017 and 036 do not express TcdA.

^fP < 0.0001, compared to ribotype 087.