PeptibodyF2-MMAE, being peptibodyF2 conjugated with a cytotoxic drug, shows high and specific cytotoxicity towards cell lines expressing FGFR1, i.e., squamous cell lung carcinoma NCI-H520, while remaining non-toxic for cells with physiological FGFR1 levels. The gene discussed is FGFR1; the disease is squamous cell lung carcinoma.