Targeting elements may be antibody fragments, such as single-chain variable fragments (scFv), single-domain antibodies (sdAb), peptides, or fatty acids, which bind to specific target molecules.

Effector elements may be scFv, sdAb, cytotoxic drugs, peptide hormones, chelators for harboring radionuclides, immunoregulatory molecules, short interference RNA, or others, which mediate or render inhibitory, stimulatory, or lethal effects on the cells in contact.

A multi-arm linker that has been conjugated with targeting or effector elements may be referred as a “packed multi-arm linker”, which can be applied as a “targeting moiety” or “effector moiety” to couple with an effector or targeting molecule (or moiety), respectively.