DENILEUKIN DIFTITOX, IS A RECOMBINANT DNA-DERIVED CYTOTOXIC PROTEIN COMPOSED OF THE AMINO ACID SEQUENCES FOR DIPHTHERIA TOXIN FRAGMENTS A AND B (MET1-THR387)-HIS AND THE SEQUENCES FOR HUMAN INTERLEUKIN-2 (IL-2; ALA1-THR133).
DENILEUKIN DIFTITOX IS A FUSION PROTEIN DESIGNED TO DIRECT THE CYTOCIDAL ACTION OF DIPHTHERIA TOXIN TO CELLS WHICH EXPRESS THE IL-2 RECEPTOR. EX VIVO STUDIES REPORT THAT AFTER BINDING TO THE IL-2 RECEPTOR ON THE CELL SURFACE, DENILEUKIN DIFTITOX IS INTERNALIZED BY RECEPTOR-MEDIATED ENDOCYTOSIS. THE FUSION PROTEIN IS SUBSEQUENTLY CLEAVED, RELEASING DIPHTHERIA TOXIN ENZYMATIC AND TRANSLOCATION DOMAINS FROM THE IL-2 FRAGMENT, RESULTING IN THE INHIBITION OF PROTEIN SYNTHESIS AND ULTIMATELY, CELL DEATH.