title: Sustained tumor regression of human colorectal cancer xenografts using a multifunctional mannosylated fusion protein in antibody-directed enzyme prodrug therapy.
abstract: OBJECTIVE
  Antibody-directed enzyme prodrug therapy (ADEPT) requires highly selective antibody-mediated delivery of enzyme to tumor. MFE-CP, a multifunctional genetic fusion protein of antibody and enzyme, was designed to achieve this by two mechanisms. First by using a high affinity and high specificity single chain Fv antibody directed to carcinoembryonic antigen. Second by rapid removal of antibody-enzyme from normal tissues by virtue of post-translational mannosylation. The purpose of this paper is to investigate these dual functions in an animal model of pharmacokinetics, pharmacodynamics, toxicity, and efficacy.
  
  
  METHODS
  MFE-CP was expressed in the yeast Pichia pastoris and purified via an engineered hexahistidine tag. Biodistribution and therapeutic effect of a single ADEPT cycle (1,000 units/kg MFE-CP followed by 70 mg/kg ZD2767P prodrug at 6, 7, and 8 hours) and multiple ADEPT cycles (9-10 cycles within 21-24 days) was studied in established human colon carcinoma xenografts, LS174T, and SW1222.
  
  
  RESULTS
  Selective localization of functional enzyme in tumors and rapid clearance from plasma was observed within 6 hours, resulting in tumor to plasma ratios of 1,400:1 and 339:1, respectively for the LS174T and SW1222 models. A single ADEPT cycle produced reproducible tumor growth delay in both models. Multiple ADEPT cycles significantly enhanced the therapeutic effect of a single cycle in the LS174T xenografts (P = 0.001) and produced regressions in the SW1222 xenografts (P = 0.0001), with minimal toxicity.
  
  
  CONCLUSIONS
  MFE-CP fusion protein, in combination with ZD2767P, provides a new and successful ADEPT system, which offers the potential for multiple cycles and antitumor efficacy. These results provide a basis for the next stage in clinical development of ADEPT.
authors.affiliation: CR UK Targeting and Imaging Group, Department of Oncology, Royal Free and University College Medical School, Royal Free Campus, Rowland Hill Street, London NW3 2PF, United Kingdom. surinder.sharma@ucl.ac.uk
authors.forename: Surinder K
authors.initials: SK
authors.lastname: Sharma
authors.forename: R Barbara
authors.initials: RB
authors.lastname: Pedley
authors.forename: Jeetendra
authors.initials: J
authors.lastname: Bhatia
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Boxer
authors.forename: Ethaar
authors.initials: E
authors.lastname: El-Emir
authors.forename: Uzma
authors.initials: U
authors.lastname: Qureshi
authors.forename: Berend
authors.initials: B
authors.lastname: Tolner
authors.forename: Helen
authors.initials: H
authors.lastname: Lowe
authors.forename: N Paul
authors.initials: NP
authors.lastname: Michael
authors.forename: Nigel
authors.initials: N
authors.lastname: Minton
authors.forename: Richard H J
authors.initials: RH
authors.lastname: Begent
authors.forename: Kerry A
authors.initials: KA
authors.lastname: Chester
mesh_terms: D000818:Animals; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D003110:Colonic Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism / Q000628:therapy*; D005260:Female; D006801:Humans; D007128:Immunoglobulin Fragments / Q000235:genetics / Q000378:metabolism; D008358:Mannose / Q000378:metabolism*; D008657:Metabolic Clearance Rate; D051379:Mice; D008819:Mice, Nude; D009588:Nitrogen Mustard Compounds / Q000493:pharmacokinetics / Q000627:therapeutic use*; D010843:Pichia / Q000378:metabolism; D011355:Prodrugs / Q000493:pharmacokinetics / Q000627:therapeutic use*; D015202:Protein Engineering; D011499:Protein Processing, Post-Translational; D011877:Radionuclide Imaging; D011993:Recombinant Fusion Proteins / Q000493:pharmacokinetics / Q000627:therapeutic use*; D014018:Tissue Distribution; D014183:Transplantation, Heterologous; D011623:gamma-Glutamyl Hydrolase / Q000235:genetics / Q000378:metabolism*
chemical_list: D002272:Carcinoembryonic Antigen; D007128:Immunoglobulin Fragments; C451184:MFE-23 protein, human; D009588:Nitrogen Mustard Compounds; D011355:Prodrugs; D011993:Recombinant Fusion Proteins; C097602:ZD 2767; D011623:gamma-Glutamyl Hydrolase; D008358:Mannose