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.
