Figure 3. Cytotoxicity induced by Spy-tagged cetuximab ADCs using EGFR overexpressing MDA-MB-468 and EGFR-negative MCF-7 breast cancer cell lines.

(A) In vitro cell killing of ADCs with non-cleavable (nc) MMAE payload 6 (■). (B) In vitro cell killing of ADCs with cleavable (vc) MMAE payload 7 (□). Incubation times were 3 days. Trastuzumab ADCs were used as isotype controls (○ and ●). Compound 6 (▼) and compound 7 (▲) were also assayed as controls. IC₅₀ values were calculated as mean values from two independent experiments.