title: Humanized ADEPT comprised of an engineered human purine nucleoside phosphorylase and a tumor targeting peptide for treatment of cancer.
abstract: Immunogenicity caused by the use of nonhuman enzymes in antibody-directed enzyme prodrug therapy has limited its clinical application. To overcome this problem, we have developed a mutant human purine nucleoside phosphorylase, which, unlike the wild-type enzyme, accepts (deoxy)adenosine-based prodrugs as substrates. Among the different mutants of human purine nucleoside phosphorylase tested, a double mutant with amino acid substitutions E201Q:N243D (hDM) is the most efficient in cleaving (deoxy)adenosine-based prodrugs. Although hDM is capable of using multiple prodrugs as substrates, it is most effective at cleaving 2-fluoro-2'-deoxyadenosine to a cytotoxic drug. To target hDM to the tumor site, the enzyme was fused to an anti-HER-2/neu peptide mimetic (AHNP). Treatment of HER-2/neu-expressing tumor cells with hDM-AHNP results in cellular localization of enzyme activity. As a consequence, harmless prodrug is converted to a cytotoxic drug in the vicinity of the tumor cells, resulting in tumor cell apoptosis. Unlike the nonhuman enzymes, the hDM should have minimal immunogenicity when used in antibody-directed enzyme prodrug therapy, thus providing a novel promising therapeutic agent for the treatment of tumors.
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of California-Los Angeles, 615 Charles E. Young Drive East, 247 BSRB, Los Angeles, CA 90095, USA. sepideha@ucla.edu
authors.forename: Sepideh
authors.initials: S
authors.lastname: Afshar
authors.forename: Tsuneaki
authors.initials: T
authors.lastname: Asai
authors.forename: Sherie L
authors.initials: SL
authors.lastname: Morrison
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000235:genetics / Q000633:toxicity; D000906:Antibodies / Q000276:immunology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D006151:Guanosine / Q000235:genetics; D006801:Humans; D007700:Kinetics; D018716:Molecular Mimicry; D009154:Mutation / Q000235:genetics; D009369:Neoplasms / Q000276:immunology / Q000378:metabolism / Q000473:pathology* / Q000628:therapy*; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D011355:Prodrugs / Q000008:administration & dosage* / Q000378:metabolism / Q000627:therapeutic use*; D015202:Protein Engineering; D011683:Purine-Nucleoside Phosphorylase / Q000235:genetics / Q000378:metabolism*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D000241:Adenosine; D000906:Antibodies; D006151:Guanosine; D010455:Peptides; D011355:Prodrugs; D011683:Purine-Nucleoside Phosphorylase; D018719:Erb-b2 Receptor Tyrosine Kinases; D011994:Recombinant Proteins