Site-specific DAR 4 ADCs
generated using the TKM ligation display high potency in in vitro
and in vivo tumor models. (A) ADCs with payloads placed at CH1 (blue),
CT (red), and Hinge (green). (B) In vitro cytotoxicity. Cells were
treated with varying concentrations of maytansine (black), compound 5 (purple), antigen-targeted ADCs conjugated at the CH1 (blue),
CT (red), or Hinge (green) positions, and an isotype control ADC (gold).
Error bars = SD; n = 9. (C,D) The in vivo efficacy
of ADCs bearing payloads at the CH1 (blue), CT (red), or hinge (green)
positions was compared to the vehicle-treated negative control group.
Mean tumor volume ((C) error bars = SEM) and survival (D) are shown.