title: Antibody targeting in metastatic colon cancer: a phase I study of monoclonal antibody F19 against a cell-surface protein of reactive tumor stromal fibroblasts.
abstract: OBJECTIVE
  To define the toxicity, imaging, and biodistribution characteristics of iodine 131-labeled monoclonal antibody F19 (131I-mAbF19). MAbF19 recognizes the fibroblast activation protein (FAP), a cell-surface glycoprotein not present in most normal tissues, but abundantly expressed by reactive stromal fibroblasts of epithelial cancers, including more than 95% of primary and metastatic colorectal carcinomas.
  
  
  METHODS
  131I-mAbF19 was administered intravenously to 17 patients with hepatic metastases from colorectal carcinoma who were scheduled for resection of localized metastases or insertion of hepatic artery catheter for regional chemotherapy. Seven to 8 days before surgery, patients received 131I-mAbF19 at three dose levels, with at least four patients entered at each level.
  
  
  RESULTS
  No toxicity associated with intravenous 131I-mAbF19 administration was observed. Tumor images were obtained on planar and single-photon emission tomography (SPECT) scans in 15 of 17 patients with hepatic metastases, tumor-infiltrated portal lymph nodes, and/or recurrent pelvic disease. The smallest lesion visualized was 1 cm in diameter. The optimal time for tumor imaging was 3 to 5 days after 131I-mAbF19 administration. The use of image registration techniques allowed precise anatomic localization of 131I-mAbF19 accumulation. Immunohistochemical analysis of biopsy tissues showed expression of FAP in the tumor stroma (but not in normal liver) in all patients studied and confirmed that the FAP-positive tumor stromal fibroblasts were interposed between the tumor capillaries and the malignant colon epithelial cells. At the time of surgery, tumor-to-liver ratios up to 21:1 and tumor-to-serum ratios up to 9:1 were obtained. The fraction of the injected 131I-mAbF19 dose per gram tumor (%ID/g tumor) localized to hepatic metastases at the time of surgery ranged from 0.001% to 0.016%.
  
  
  CONCLUSIONS
  The FAP tumor fibroblast antigen is highly expressed in primary and metastatic colorectal carcinomas and shows limited expression in normal adult tissues. This highly selective expression pattern allows imaging of colorectal carcinoma lesions as small as 1 cm in diameter on 131I-mAbF19 scans. Because of the consistent presence of FAP in the stroma of epithelial cancers and the accessibility of FAP-positive tumor stromal fibroblasts to circulating monoclonal antibodies (mAbs), this study suggests possible diagnostic and therapeutic applications of humanized mAbF19 and mAbF19 constructs with novel immune and nonimmune effector functions.
authors.affiliation: Ludwig Institute for Cancer Research, New York Unit, NY.
authors.forename: S
authors.initials: S
authors.lastname: Welt
authors.forename: C R
authors.initials: CR
authors.lastname: Divgi
authors.forename: A M
authors.initials: AM
authors.lastname: Scott
authors.forename: P
authors.initials: P
authors.lastname: Garin-Chesa
authors.forename: R D
authors.initials: RD
authors.lastname: Finn
authors.forename: M
authors.initials: M
authors.lastname: Graham
authors.forename: E A
authors.initials: EA
authors.lastname: Carswell
authors.forename: A
authors.initials: A
authors.lastname: Cohen
authors.forename: S M
authors.initials: SM
authors.lastname: Larson
authors.forename: L J
authors.initials: LJ
authors.lastname: Old
mesh_terms: D000368:Aged; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology; D014408:Biomarkers, Tumor; D003110:Colonic Neoplasms / Q000276:immunology* / Q000473:pathology; D010450:Endopeptidases; D005260:Female; D005347:Fibroblasts / Q000276:immunology*; D018093:Gelatinases; D006133:Growth Substances / Q000276:immunology*; D006801:Humans; D007457:Iodine Radioisotopes; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000276:immunology / Q000556:secondary; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging; D008297:Male; D008565:Membrane Proteins; D008875:Middle Aged; D009362:Neoplasm Metastasis / Q000000981:diagnostic imaging*; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging; D016719:Radioimmunodetection; D016499:Radioimmunotherapy; D012697:Serine Endopeptidases; D015899:Tomography, Emission-Computed, Single-Photon; D000099167:Fibroblast Activation Protein Alpha
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D014408:Biomarkers, Tumor; D010450:Endopeptidases; D018093:Gelatinases; D006133:Growth Substances; D007457:Iodine Radioisotopes; D008565:Membrane Proteins; D012697:Serine Endopeptidases; D000099167:Fibroblast Activation Protein Alpha