immunotoxin

noun

im·​mu·​no·​tox·​in ˈim-yə-nō-ˌtäk-sən  im-ˈyü-nō- 

: a toxin that is linked to a monoclonal antibody and that is delivered to only those cells (as cancer cells) bearing the antigen targeted by the monoclonal antibody to which it is linked