The present invention relates to Multifunctional Antibody Conjugates, comprising an antibody or antigen binding portion thereof, comprising at least a fragment of a light chain constant kappa region (CLK) comprising K188according to Kabat numbering; a linker comprising the formula X-Y-Z, wherein Z is a group is covalently connected to the antibody through the side chain of K188, Y is a linear or branched biologically compatible connecting chain, and X is a group covalently connected to at least one Effector Moiety.The invention further provides specific MAC compounds and compositions of the invention.本發明關於多功能抗體共軛物類(MACs),其包含抗體或彼之抗原結合部分及連接子,該抗體或彼之抗原結合部分包含至少輕鏈κ恆定區(CLκ)之片段,該片段包含根據卡巴(Kabat)編號之K188,且該連接子包含式X-Y-Z,其中Z係透過K188之側鏈與該抗體共價連接之基團,Y係線性或分歧之生物相容性連接鏈且X係與至少一個效應基團共價連接之基團。本發明另提供本發明之特定MAC化合物及組成物。