Fusion proteins are recombinant molecules that combine a targeting mechanism to a
cytocidal moiety. DAB 389 IL-2 (denileukin diftitox; ONTAK™), with a unique mechanism of
action, is the first genetically constructed fusion protein to reach the clinic. In this molecule,
the interleukin-2 (IL-2) gene is genetically fused to the enzymatically active and translocating
domains of diphtheria toxin. DAB 389 IL-2 is internalized into IL-2 receptor-bearing cells by
endocytosis. The ADP-ribosyltransferase activity of diphtheria toxin is cleaved in the …