The present inventors succeeded in producing: an anti Epiregulin antibody exhibiting a cross species reactivity between a non human animal crab eating monkey and a human animal an anti Epiregulin antibody with suppressed chemical decomposition an anti Epiregulin antibody having a lowered isoelectric point an anti Epiregulin antibody having an elevated thermal denaturation midpoint temperature and an anti Epiregulin antibody having a reduced amount of aggregates by appropriately substituting an amino acid residue in the variable region sequence of a humanized EP27 antibody that is capable of exhibiting a cytotoxic activity and neutralization activity on a cancer cell said cancer cell expressing human Epiregulin to thereby inhibit the proliferation of the cancer cell. Also the present inventors succeeded in creating a therapeutic agent for non small cell lung carcinoma excluding adenocarcinoma said therapeutic agent comprising one of the aforesaid antibodies as an active ingredient.
