title: Biodistribution and efficacy of [131I]A33scFv::CDy, a recombinant antibody-enzyme protein for colon cancer.
abstract: In antibody-directed enzyme-prodrug therapy (ADEPT), an antibody-bound enzyme localizes to tumor tissue, where it selectively converts a subsequently administered non-toxic prodrug into a cytotoxic drug. A33scFv::CDy is a bifunctional fusion construct comprising a single chain antibody against the gpA33 antigen and the prodrug-converting enzyme cytosine deaminase. gpA33 is highly and homogeneously expressed in >95% of all colorectal cancers. Here we describe the biodistribution and tumor-targeting capacity of 131I labeled A33scFv::CDy. 131I labeling of A33scFv::CDy was performed by the chloramine-T method, and the properties of the resulting [131I]A33scFv::CDy conjugate were determined in vivo and in vitro, including biodistribution studies in nude mice bearing human LIM1215 colon carcinoma xenografts. The [131I]A33scFv::CDy conjugate bound specifically to colorectal cancer cells in vitro with KD = 15.8 nM as determined by a saturation assay. in vivo, the tumor uptake of [131I]A33scFv::CDy peaked at 87% injected dose/g 47 h post injection. Normal tissue uptake was low, and activity in blood was lower than in tumor at all time-points studied (6-92 h). The tumor-to-blood ratio increased over time with a maximum of 8.1 at 67 h post injection. [131I]A33scFv::CDy thus shows a biodistribution that makes it attractive for both radioimmunotherapy (RIT) and ADEPT. Preliminary therapeutic experiments showed a significant reduction of tumor size in mice treated with the A33scFv::CDy-5-fluorocytosine/5-fluorouracil ADEPT system. This work demonstrates the feasibility of ADEPT and RIT based on the A33scFv::CDy recombinant construct.
authors: Medizinische Klinik mit Schwerpunkt Hämatologie und Onkologie CBF, D-12200 Berlin, Germany.
authors: Hossein
authors: H
authors: Panjideh
authors: Vania Casimiro
authors: VC
authors: Da Silva Coelho
authors: Jens
authors: J
authors: Dernedde
authors: Christopher
authors: C
authors: Bachran
authors: Gregor J
authors: GJ
authors: Förster
authors: Jürgen
authors: J
authors: Franke
authors: Patricia
authors: P
authors: Fasold
authors: Hendrik
authors: H
authors: Fuchs
authors: Eckhard
authors: E
authors: Thiel
authors: P Markus
authors: PM
authors: Deckert
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D007128:Immunoglobulin Fragments / Q000378:metabolism / Q000627:therapeutic use*; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008562:Membrane Glycoproteins / Q000276:immunology*; D051379:Mice; D016499:Radioimmunotherapy; D011993:Recombinant Fusion Proteins / Q000493:pharmacokinetics / Q000627:therapeutic use*; D014018:Tissue Distribution
chemical_list: C104258:GPA33 protein, human; D007128:Immunoglobulin Fragments; D007457:Iodine Radioisotopes; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; C055966:immunoglobulin Fv