A Humanized Anti-CD22-Onconase Antibody-Drug Conjugate Mediates Highly Potent Destruction of Targeted Tumor Cells

Table 2

Dose- and DAR-dependent in vitro cytotoxicity of SPDP-based ADCs.

	OAR	Daudi	Nalm6	Jurkat
		IC50  ± SE (nM)	IC50  ± SE (nM)	IC50  ± SE (nM)
ONC	—	1,469 ± 44.50	503.2 ± 21.67	674.5 ± 99.5
huRFB4 IgG	—	>500	>500	>500
SPDP-based 162 kDa ADC	1 : 1	260.0	>284	ND
SPDP-based 174 kDa ADC	2 : 1	0.68 ± 0.30	2.20 ± 2.07	>390
SPDP-based 186 kDa ADC	3 : 1	0.08 ± 0.02	0.14 ± 0.02	>335

The concentration required to inhibit cell viability by 50% relative to buffer-treated control cells (IC₅₀) was determined from semilogarithmic plots in which viability as percentage of control was plotted versus the tested protein concentration. IC₅₀ values are expressed as mean ± SE and are derived from at least two independent experiments each performed in triplicate. ND: not determined.