The present invention concerns a multivalent antibody construct comprising an anti-IGF-1R antibody or antigen-binding fragment thereof, wherein the anti-IGF-1R antibody or antigen-binding fragment thereof comprises the heavy chain variable region complementarity determining region (CDR) sequences CDR1 (DYYMY, SEQ ID NO: 1), CDR2 (YITNYGGSTYYPDTVKG, SEQ ID NO:2) and CDR3 (QSNYDYDGWFAY, SEQ ID NO:3) and the light chain variable region CDR sequences CDR1 (KASQEVGTAVA, SEQ ID NO:4), CDR2 (WASTRHT, SEQ ID NO:5) and CDR3 (QQYSNYPLT, SEQ ID NO:6.