The invention provides an isolated antibody, or one of its functional fragments, said fragments being capable of binding to the human insulin-like growth factor I receptor IGF-IR, 5 characterized in that it comprises: a light chain comprising at least the 3 complementarity determining regions (CDRs) of sequence SEQ ID Nos. 2, 4 and 6, or comprising said 3 CDRs whose sequence has a substitution of one amino acid； or a heavy chain comprising at least the 3 CDRs of sequence SEQ ID Nos. 8, 10 and 0 12, or comprising solid 3 CDRs whose sequence has a substitution of one amino acid, wherein said substitution of one amino acid is a substitution which replaces leucine by valine or isoleucine, aspartic acid by glutamic acid, glutamine by asparagine, arginine by lysine or the reverse substitution 5 thereof. The invention also provides methods of using the antibodies.
