The present invention relates to antibody-drug conjugates (ADCs) wherein a plurality of active agents are conjugated to an antibody through at least one branched linker. The branched linker may comprise a branching unit, and two active agents are coupled to the branching unit through a secondary linker and the branching unit is coupled to the antibody by a primary linker. The active agents may be the same or different. In certain such embodiments, two or more such branched linkers are conjugated to the antibody, e.g., 2-4 branched linkers, which may each be coupled to a different C-terminal cysteine of a heavy or light chain of the antibody. The branched linker may comprise one active agent coupled to the branching unit by a first branch and a second branch that comprises a polyethylene glycol moiety coupled to the branching unit. In certain such embodiments, two or more such branched linkers are conjugated to the antibody, e.g., 2-4 branched linkers, which may each be coupled to a different C-terminal cysteine of a heavy or light chain of the antibody.
