Immunotoxin

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Schematic representation of the endocytosis of an immunotoxin in a cancer cell.

Immunotoxins , also known as immunotoxins , are immunoconjugates that consist of a cell-binding component and a toxin . Immunotoxins are potential drugs that especially in oncology for the treatment of cancer are to be used ( cancer immunotherapy ).

Structure and synthesis

Immunotoxins are made up of two components. One component is a carrier molecule that binds to cancer cells as selectively as possible. In most cases this is a monoclonal antibody or a fragment of a monoclonal antibody or a corresponding antibody mimetic . The carrier molecule serves on the one hand as a ligand for binding to the target structure ( target ) on the cell membrane of a cancer cell. By definition, the ligand is derived from the immune system. The target structures are essentially tumor antigens or tumor-specific receptors, i.e. proteins or glycoproteins which , ideally , are only presented ( expressed ) by cancer cells on their cell surface . The other function of the carrier molecule is to attach a toxin - the second component of an immunotoxin. Toxins are highly toxic compounds of vegetable or bacterial origin. Protein-based toxins are used almost exclusively for immunotoxins. In the first immunotoxins, antibodies and toxins were synthesized separately and then linked to one another via chemical linkers . Immunotoxins are now produced completely recombinantly , i.e. with the help of genetically modified microorganisms ( fusion proteins ). In this way, immunotoxins can also be produced that only consist of the binding domain of the antibody and an active portion of the toxin.

When toxins are vegetable toxins, such as ricin , saporin (a toxin the ribosome inactive), bryodin 1 (a likewise ribosome deactivating toxin of the red-fruited bryony ( Bryonia dioica )), Bouganin (a toxin of the type Bougainvillea spectabilis from the genus of Bougainvillea ), gelonin (a toxin from Gelonium multiflorum ) or pokeweed antiviral protein (PAP, American pokeweed = American pokeweed = Phytolacca americana ), and bacterial toxins such as diphtheria toxin , listeriolysin O , exotoxin a ( Pseudomonas exotoxin ), or anthrax toxin , for Application.

In the meantime, mainly bacterial toxins, or their toxin segments, are used. This is due, among other things, to the sometimes unfavorable enzymatic processing and release of these immunotoxins in the lysosome, as well as the transition to recombinantly produced immunotoxins. If the cell-binding region of the toxin is deleted from the corresponding gene which codes for the toxin , the application safety of the immunotoxin can be increased. For the most part, only the toxins absorbed via the carrier molecule are effective in the cell. Free toxins, for example enzymatically split off from the carrier molecule, are not. In principle, several toxin molecules can also be bound to one antibody.

Working principle

Via the ligand (antibody, antibody fragment or antibody mimetic), the immunotoxin binds preferentially to the cells that express the corresponding receptor, for example a tumor antigen, on their surface. An immune complex is formed from ligand and receptor ( lock and key principle ). The immunotoxin is internalized by the cell to whose surface it is bound by means of receptor-mediated endocytosis and broken down in the lysosome . The toxin is released and can develop its effect. The effect is toxin-dependent. Some toxins destroy the cell membrane, others deactivate the ribosomes or similar essential proteins in the cytosol . The damage to the cell triggers apoptosis (programmed cell death). In the case of catalytically active toxins, such as diphtheria toxin, in many cases a single molecule in a cell is sufficient to kill them.

Status of development

The first concepts for immunotoxins date back to the early 1980s. A number of immunotoxins are currently in clinical trials. No antibody-based immunotoxin is currently approved as a drug. The main problems lie in the short plasma half-life of the currently tested immunotoxins and the associated rapid elimination from the body, as well as other causes described in the next paragraph .

In 1999, Denileukin Diftitox was the first immunotoxin to be approved by the FDA for the treatment of refractory patients with cutaneous T-cell lymphoma in the United States . It does not consist of an antibody, but of interleukin-2 , to which the diphtheria toxin is bound. The interleukin-2 binds to the interleukin-2 receptor, which is mainly expressed by T lymphocytes - including malignant T lymphocytes. Denileukin Diftitox is not approved as a medicinal product in Europe.

Limitations and potential

The best results in clinical studies have so far been achieved in hematological cancers - mainly T-cell lymphomas and leukemias. For other cancers, especially solid tumors, the results so far have been rather disappointing. In many cases, the side effects were considerable, due to an excessively high level of binding to healthy tissue. The cause here was insufficient specificity for cancer cells. The cells of the liver and kidneys in particular are damaged by the healthy cells of the body . A promising approach to solving this problem is the use of bispecific immunotoxins. This involves combining scFv fragments with two different ligands with a single toxin, increasing the likelihood of binding to a cancer cell. A very common side effect in the immunotoxins of the first generation on the basis of ricin, which is systemic capillary leak syndrome (engl. Vascular leakage syndrome , ultimately, the dose of the immunotoxin, VLS) limited. This problem does not exist with bacterial toxin segments. Modified ricin sequences are now available in which this side effect is largely eliminated.

Another difficulty is the poor tumor penetration of the immunotoxins. The recombinantly produced immunotoxins show some advantages over chemically coupled immunotoxins. This problem can be partly overcome by reducing the size of the ligand, for example by using Fab or scFv fragments, which have a higher penetration capacity into the tissue. It is also possible to reduce the size of the toxin by deleting less active areas.

Many patients develop an immune response against the immunotoxins, for example because they have previously formed antibodies against the naturally occurring toxins. Some toxins are enzymatically broken down in the cancer cells in the lysosome and then remain without effect in the cell.

Despite these limitations and problems, immunotoxins - even with solid tumors - have a high therapeutic potential. While in conventional chemotherapy, for example, necrotic dormant areas of a tumor often do not respond to the therapy or have developed resistance, immunotoxins can also trigger apoptosis there. Immune toxins can also trigger apoptosis in drug-resistant cells ( multiple drug resistance ).

further reading

Reference books

  • C. Huber (editor) among others: Cancer immunotherapies. Deutscher Ärzteverlag, 2007, ISBN 3-769-11212-1 .
  • WA Hall: Immunotoxin Methods and Protocols. Humana Press, 2000, ISBN 0-896-03775-4 .
  • K. Kawakami et al: Cytotoxins and immunotoxins for cancer therapy. Routledge Chapman & Hall, 2004, ISBN 0-415-26365-4 .
  • ML Grossbard: Monoclonal antibody-based therapy of cancer. Informa Healthcare, 1998, ISBN 0-824-70196-8 .
  • M. Welschof and J. Krauss: Recombinant antibodies for cancer therapy. Verlag Springer, 2002, ISBN 0-896-03918-8 .
  • GT Hermanson: Bioconjugate techniques. Academic Press, 2008, ISBN 0-123-70501-0 .

Review article

Technical article

  • S. Barth et al.: Immunotoxins - Mode of action and use in malignant diseases. In: Der Internist 38, 1997, pp. 1063-1069. PMID 9453955 doi : 10.1007 / s001080050118
  • M. Mathew, RS Verma: Humanized immunotoxins: a new generation of immunotoxins for targeted cancer therapy In: Cancer Sci. 100, 2009, pp. 1359-1365 PMID 19459847 (Review)
  • AE Frankel: New anti-T cell immunotoxins for the clinic. In: Leukemia Research 29, 2005, pp. 249-251. PMID 15661259

Dissertations

Web links

Individual evidence

  1. ^ RJ Kreitmann: Recombinant immunotoxins containing truncated bacterial toxins for the treatment of hematologic malignancies. In: BioDrugs 23, 2009, pp. 1-13. PMID 19344187 doi : 10.2165 / 00063030-200923010-00001 (Review).
  2. ^ SR Schmidt: Fusion-proteins as biopharmaceuticals -applications and challenges. In: Curr Opin Drug Discov Devel 12, 2009, pp. 284-295. PMID 19333874 (Review).
  3. ↑ a b c M. Mathew, RS Verma: Humanized immunotoxins: a new generation of immunotoxins for targeted cancer therapy In: Cancer Sci. 100, 2009, pp. 1359-1365 PMID 19459847 (review).
  4. ↑ a b T. Lich and others: Treatment of advanced gastric carcinomas with recombinant immunotoxins. In: Journal Onkologie 4, 2004.
  5. ^ AE Frankel et al.: Therapy of patients with T-cell lymphomas and leukemias using an anti-CD7 monoclonal antibody-ricin A chain immunotoxin. In: Leukemia & Lymphoma 26, 1997, pp. 287-298. PMID 9322891
  6. ↑ MJ Glennie et al .: Emergence of immunoglobulin variants following treatment of a B cell leukemia with an immunotoxin composed of antiidiotypic antibody and saporin. In: J Exp Med 166, 1987, pp. 43-62. PMID 3110351
  7. ↑ DJ Flavell: Saporin immunotoxins. In: Curr Top Microbiol Immunol 234, 1998, pp. 57-61. PMID 9670612 (Review)
  8. ↑ F. Stirpe et al .: Selective cytotoxic activity of immunotoxins composed of a monoclonal anti-Thy 1.1 antibody and the ribosome-inactivating proteins bryodin and momordin. In: Br J Cancer 58, 1988, pp. 558-561. PMID 3265330
  9. ↑ JA Francisco et al: Construction, expression, and characterization of BD1-G28-5 sFv, a single-chain anti-CD40 immunotoxin containing the ribosome-inactivating protein bryodin 1. In: J Biol Chem 272, 1997, pp. 24165-24169 . PMID 9305866
  10. ↑ J. Cizeau et al .: Engineering and biological characterization of VB6-845, an anti-EpCAM immunotoxin containing a T-cell epitope-depleted variant of the plant toxin bouganin. In: Journal of Immunotherapy 32, 2009, pp. 574-584. PMID 19483652
  11. ↑ MG Rosenblum et al .: Design, expression, purification, and characterization, in vitro and in vivo, of an antimelanoma single-chain Fv antibody fused to the toxin gelonin. In: Cancer Res 63, 2003, pp. 3995-4002. PMID 12873997
  12. ↑ B. Jansen et al: Establishment of a human t (4; 11) leukemia in severe combined immunodeficient mice and successful treatment using anti-CD19 (B43) -pokeweed antiviral protein immunotoxin. In: Cancer Res 52, 1992, pp. 406-412. PMID 1370213
  13. ^ AE Frankel et al.: Anti-CD3 recombinant diphtheria immunotoxin therapy of cutaneous T cell lymphoma. In: Curr Drug Targets 10, 2009, pp. 104-109. PMID 19199905 (Review)
  14. ↑ S. Potala et al .: Targeted therapy of cancer using diphtheria toxin-derived immunotoxins. In: Drug Discov Today 13, 2008, pp. 807-815. PMID 18678276 (Review)
  15. ^ AE Frankel et al: Diphtheria toxin conjugate therapy of cancer. In: Cancer Chemother Biol Response Modif 20, 2002, pp 301-313. PMID 12703211 (Review)
  16. ↑ a b S. Bergelt et al .: Listeriolysin O as cytotoxic component of an immunotoxin. In: Protein Sci 18, 2009, pp. 1210-1220. PMID 19472336
  17. ↑ RJ Kreitman: Chimeric fusion proteins - Pseudomonas exotoxin-based. In: Curr Opin Investig Drugs 2, 2001, pp. 1282-1293. PMID 11717817 (Review)
  18. ^ I. Pastan: Immunotoxins containing Pseudomonas exotoxin A: a short history. In: Cancer Immunol Immunother 52, 2003, pp. 338-341. PMID 12700949 (Review)
  19. ↑ a b A. E. Frankel et al.: Anthrax fusion protein therapy of cancer. In: Curr Protein Pept Sci 3, 2002, pp. 399-407. PMID 12370003 (Review)
  20. ↑ a b c I. Pastan et al: Immunotoxin therapy of cancer. In: Nat Rev Cancer 6, 2006, pp. 559-565. PMID 16794638 (Review)
  21. ↑ DJ Flavell and SU Flavell: Comparison of immunotoxins bearing a single saporin molecule with multiple toxin conjugates. In: Methods Mol Biol 166, 2001, pp. 87-100. PMID 11217378 (Review)
  22. ↑ a b c A. E. Frankel and JH Woo: Bispecific immunotoxins. In: Leuk Res 33, 2009, pp. 1173-1174. PMID 19406472
  23. ↑ a b c D. A. Vallera et al .: Genetic alteration of a bispecific ligand-directed toxin targeting human CD19 and CD22 receptors resulting in improved efficacy against systemic B cell malignancy. In: Leuk Res 33, 2009, pp. 1233-1242. PMID 19327829
  24. ↑ D. Scharma et al.: Antibody targeted drugs as cancer therapeutics. In: Nat Rev Drug Discov 5, 2006, pp. 147-159. PMID 16424916 (Review)
  25. ↑ HP Zenner: Experimental chemotherapy: selective-toxic antibody-toxin hybrids against larynx carcinoin cells. In: European Archives of Oto-Rhino-Laryngology pp. 406-409. doi : 10.1007 / BF00459857
  26. ↑ X. Liu et al: Novel strategies to augment genetically delivered immunotoxin molecular therapy for cancer therapy. In: Cancer Gene Ther 2009 [Epub ahead of print] PMID 19461676
  27. ↑ F. Turturro: Denileukin diftitox: a biotherapeutic paradigm shift in the treatment of lymphoid-derived disorders. In: Expert Rev Anticancer Ther 7, 2007, pp. 11-17. PMID 17187516 doi : 10.1586 / 14737140.7.1.11
  28. ↑ C. Huber (editor) among others: Cancer immunotherapies. Deutscher Ärzteverlag, 2007, ISBN 3-769-11212-1 , p. 129
  29. ↑ Mycosis fungoides. Accessed July 9, 2009
  30. ^ NH Dang et al: Phase II trial of denileukin diftitox for relapsed / refractory T-cell non-Hodgkin's lymphoma. In: Br J Haematol 136, 2007, pp. 439-447. PMID 17233846
  31. ↑ RJ Kreitman et al .: Phase I trial of recombinant immunotoxin RFB4 (dsFv) -PE38 (BL22) in patients with B-cell malignancies. In: J Clin Oncol 23, 2005, pp. 6719-6729. PMID 16061911
  32. ↑ a b I. Heisler: Importance of cleavable peptide linkers for the function of recombinant saporin-EGF immunotoxins. Dissertation, FU Berlin, 2003
  33. ↑ R. Baluna and ES Vitetta: Vascular leak syndrome: a side effect of immunotherapy. In: Immunopharmacology 37, 1997, pp. 117-132. PMID 9403331 (Review)
  34. ↑ JE Smallshaw include: Genetic engineering of an immunotoxin to eliminate pulmonary vascular leak in mice. In: Nature Biotechnol 21, 2003, pp. 387-391. PMID 12627168
  35. ↑ PS Multani et al: Phase II clinical trial of bolus infusion anti-B4 blocked ricin immunoconjugate in patients with relapsed B-cell non-Hodgkin's lymphoma. In: Clin Cancer Res 4, 1998, pp. 2599-2604. PMID 9829722
  36. ^ PJ Hudson and C. Souriau: Engineered antibodies. In: Nat Med 9, 2003, pp. 129-134. PMID 12514726 (Review)
  37. ^ AE Frankel et al.: Targeted toxins. In: Clin Cancer Res 6, 2000, pp. 326-334. PMID 10690507 (Review)
  38. ^ A. Keppler-Hafkemeyer et al .: Apoptosis induced by immunotoxins used in the treatment of hematologic malignancies. In: Int J Cancer 87,2000, pp. 86-94. PMID 10861457
  39. ↑ DJ FitzGerald et al .: A monoclonal antibody-Pseudomonas toxin conjugate that specifically kills multidrug-resistant cells. In: PNAS 84, 1987, pp. 4288-4292. PMID 3495806
  40. ↑ GH Mickisch et al .: Pseudomonas exotoxin conjugated to monoclonal antibody MRK16 specifically kills multidrug resistant cells in cultured renal carcinomas and in MDR-transgenic mice. In: J Urol . 149, 1993, pp. 174-178. PMID 8417204
  41. ↑ AE Frankel et al.: Cell-specific modulation of drug resistance in acute myeloid leukemic blasts by diphtheria fusion toxin, DT388-GMCSF. In: Bioconjug Chem 9, 1998, pp. 490-496. PMID 9667951
  42. ↑ JP Perentesis et al .: Induction of apoptosis in multidrug-resistant and radiation-resistant acute myeloid leukemia cells by a recombinant fusion toxin directed against the human granulocyte macrophage colony-stimulating factor receptor. In: Clin Cancer Res 3, 1997, pp. 347-355. PMID 9815691