title: Comparison of monoclonal antibodies 17-1A and 323/A3: the influence of the affinity on tumour uptake and efficacy of radioimmunotherapy in human ovarian cancer xenografts.
abstract: The low-affinity monoclonal antibody (MAb) chimeric 17-1A(c-17-1A) and the high-affinity MAb mouse 323/A3 (m-323/A3) were used to study the effect of the MAb affinity on the tumour uptake and efficacy of radioimmunotherapy in nude mice bearing subcutaneously the human ovarian cancer xenografts FMa, OVCAR-3 and Ov.Pe. Both MAbs are directed against the same pancarcinoma glycoprotein. In vitro, the number of binding sites on tumour cells at 4 degrees C was similar for both MAbs, but m-323/A3 had an approximately 5-fold higher affinity (1.3-3.0x10(9) M-1) than c-17-1A (3.0-5.4x10(8) M-1). This difference in affinity was more extreme at 37 degrees C, when no binding of c-17-1A could be observed. MAb m-323/A3 completely blocked binding of c-17-1A to tumour cells, whereas the reverse was not observed. Immunohistochemistry showed a similar but more intense staining pattern of m-323/A3 in human ovarian cancer xenografts than of c-17-1A. In vivo, the blood clearance in non-tumour-bearing nude mice was similar for both MAbs with terminal half-lives of 71.4 h for m-323/A3 and 62.7 h for c-17-1A. MAb m-323/A3 targeted better to tumour tissue, but was more heterogeneously distributed than c-17-1A. The cumulative absorbed radiation dose delivered by m-323/A3 to tumour tissue was 2.5- to 4.7-fold higher than that delivered by c-17-1A. When mice were treated with equivalent radiation doses of 131(I)m-323/A3 and 131(I)c-17-1A, based on a correction for the immunoreactivity of the radiolabelled MAbs, m-323/A3 induced a better growth inhibition in two of the three xenografts. When the radiation doses were adjusted to obtain a similar amount of radiation in the tumour c-17-1A was more effective in tumour growth inhibition in all three xenografts.
authors.affiliation: Department of Medical Oncology, Free University Hospital, Amsterdam, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Kievit
authors.forename: H M
authors.initials: HM
authors.lastname: Pinedo
authors.forename: H M
authors.initials: HM
authors.lastname: Schlüper
authors.forename: H J
authors.initials: HJ
authors.lastname: Haisma
authors.forename: E
authors.initials: E
authors.lastname: Boven
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000378:metabolism / Q000627:therapeutic use; D000915:Antibody Affinity; D001667:Binding, Competitive; D001692:Biological Transport; D002460:Cell Line; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology / Q000378:metabolism / Q000627:therapeutic use; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics / Q000627:therapeutic use; D051379:Mice; D008819:Mice, Nude; D015999:Multivariate Analysis; D009368:Neoplasm Transplantation; D010051:Ovarian Neoplasms / Q000276:immunology / Q000378:metabolism / Q000532:radiotherapy*; D011993:Recombinant Fusion Proteins / Q000493:pharmacokinetics; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D007457:Iodine Radioisotopes; D011993:Recombinant Fusion Proteins