We have chosen human lung cancer cell lines showing FGFR1 overexpression(NCI-H520 and NCI-H1581) and a cell line with physiological, low levelsof FGFR1 (HCC95) as a control,30,45 and we used them forthe assessment of peptibodyC19-PEG4vcMMAE cytotoxicity.One of the most important issues in the drug delivery system is thechosen selective and nontoxic carrier; therefore, FGFR1-positive andFGFR1-negative cells were treated with a range of either peptibodyC19or peptibodyC19-PEG4vcMMAE concentrations. The gene discussed is FGFR1; the disease is lung carcinoma.