Cytotoxic and antitumor activity of a recombinant immunotoxin composed of disulfide-stabilized anti-Tac Fv fragment and truncated Pseudomonas exotoxin

Int J Cancer. 1994 Jul 1;58(1):142-9. doi: 10.1002/ijc.2910580123.


Disulfide-stabilized Fv (dsFv)-immunotoxins are recombinant immunotoxins in which the inherently unstable Fv moiety, composed of the VH-VL heterodimer, is stabilized by a disulfide bond engineered between structurally conserved framework positions of VH and VL. Anti-Tac(dsFv)-PE38KDEL is composed of such a dsFv, directed to the alpha subunit of the IL2 receptor (IL2R), and containing a truncated form of Pseudomonas exotoxin (PE38KDEL). We have found this new type of immunotoxin to be indistinguishable in its in vitro activity and specificity from its single-chain immunotoxin counterpart, anti-Tac(Fv)-PE38KDEL. We have now examined the therapeutically relevant factors, including stability, pharmacokinetics, and antitumor activity of this new disulfide-stabilized Fv-immunotoxin. We found that anti-Tac(dsFv)-PE38KDEL was specifically cytotoxic to human activated T-lymphocytes in addition to IL2R bearing cell lines. Anti-Tac(dsFv)-PE38KDEL was considerably more stable at 37 degrees C in human serum and in buffered saline than the single-chain immunotoxin, anti-Tac(Fv)-PE38KDEL. The half-life in blood was similar for both immunotoxins (approx. 20 min). The therapeutic potential of the disulfide-stabilized immunotoxin was evaluated using an animal model of immunodeficient mice bearing subcutaneous tumor xenografts of human IL2R-bearing cells. Anti-Tac(dsFv)-PE38KDEL caused complete regression of tumors with no toxic effects in mice. Because dsFv-immunotoxins are more stable and can be produced with significantly improved yields compared to scFv-immunotoxins, dsFv-immunotoxin may be more useful for therapeutic applications.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ADP Ribose Transferases*
  • Animals
  • Antineoplastic Agents / pharmacokinetics*
  • Antineoplastic Agents / toxicity*
  • Bacterial Toxins*
  • Disulfides / pharmacology*
  • Drug Stability
  • Exotoxins / pharmacokinetics*
  • Exotoxins / toxicity*
  • Female
  • Humans
  • Immunoglobulin Fragments / immunology
  • Immunoglobulin Variable Region / toxicity
  • Immunotoxins / metabolism*
  • Immunotoxins / toxicity*
  • Mice
  • Mice, Inbred BALB C
  • Mice, Nude
  • Neoplasm Transplantation
  • Neoplasms, Experimental / drug therapy
  • Neoplasms, Experimental / immunology
  • Peptide Fragments / immunology
  • Peptide Fragments / pharmacokinetics
  • Peptide Fragments / toxicity
  • Plasmids
  • Receptors, Interleukin-2 / immunology*
  • Recombinant Proteins / toxicity
  • Virulence Factors*


  • Antineoplastic Agents
  • Bacterial Toxins
  • Disulfides
  • Exotoxins
  • Immunoglobulin Fragments
  • Immunoglobulin Variable Region
  • Immunotoxins
  • Peptide Fragments
  • Receptors, Interleukin-2
  • Recombinant Proteins
  • Virulence Factors
  • immunoglobulin Fv
  • ADP Ribose Transferases
  • toxA protein, Pseudomonas aeruginosa