The present inventors provide methods for modifying the isoelectric point of an antibody while retaining its antigen-binding activity, comprising modifying the charge of at least one exposable amino acid residue on the surface of the complementarity determining region (CDR). The present invention also provides methods for purifying multispecific antibodies, comprising modifying isoelectric point, and methods for improving the plasma pharmacokinetics of antibodies with a modified isoelectric point. The present invention further provides antibodies with a modified isoelectric point, pharmaceutical compositions comprising the antibodies as an active ingredient, and methods for producing the antibodies and compositions.
