Prolonged in vivo tumour retention of a human diabody targeting the extracellular domain of human HER2/neu

• Published in: British journal of cancer 1998-05, Vol.77 (9), p.1405-1412
• Main Authors: Adams, GP, Schier, R, McCall, AM, Crawford, RS, Wolf, EJ, Weiner, LM, Marks, JD
• Format: Article
• Language: English
• Subjects: Animals; Antibody Affinity; Antigens, Neoplasm - immunology; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Cancer Research; Dimerization; Drug Resistance; Epidemiology; experimental-oncology; Host-tumor relations. Immunology. Biological markers; Humans; Immunoglobulin Heavy Chains - administration & dosage; Immunoglobulin Heavy Chains - metabolism; Immunoglobulin Light Chains - administration & dosage; Immunoglobulin Light Chains - metabolism; Immunotherapy - methods; Immunotoxins - administration & dosage; Immunotoxins - metabolism; Medical sciences; Mice; Mice, SCID; Molecular Medicine; Oncology; Receptor, ErbB-2 - immunology; Tissue Distribution; Tumors
• ISSN: 0007-0920; 1532-1827
• DOI: 10.1038/bjc.1998.233

Single-chain Fv (scFv) molecules exhibit highly specific tumour-targeting properties in tumour-bearing mice. However, because of their smaller size and monovalent binding, the quantities of radiolabelled scFv retained in tumours limit their therapeutic applications. Diabodies are dimeric antibody-based molecules composed of two non-covalently associated scFv that bind to antigen in a divalent manner. In vitro, diabodies produced from the anti-HER2/neu (c-erbB-2) scFv C6.5 displayed approximately 40-fold greater affinity for HER2/neu by surface plasmon resonance biosensor measurements and significantly prolonged association with antigen on the surface of SK-OV-3 cells (t1/2 cell surface retention of > 5 h vs 5 min) compared with C6.5 scFv. In SK-OV-3 tumour-bearing scid mice, radioiodinated C6.5 diabody displayed a highly favourable balance of quantitative tumour retention and specificity. By as early as 4 h after i.v. administration, significantly more diabody was retained in tumour (10 %ID g(-1)) than in blood (6.7 %ID ml(-1)) or normal tissue (liver, 2.8 %ID g(-1); lung, 7.1 %ID g(-1); kidney, 5.2 %ID g(-1)). Over the next 20 h, the quantity present in blood and most tissues dropped approximately tenfold, while the tumour retained 6.5 %ID g(-1) or about two-thirds of its 4-h value. In contrast, the 24-h tumour retention of radioiodinated C6.5 scFv monomer was only 1 %ID g(-1). When diabody retentions were examined over the course of a 72-h study and cumulative area under the curve (AUC) values were determined, the resulting tumor-organ AUC ratios were found to be superior to those previously reported for other monovalent or divalent scFv molecules. In conclusion, the diabody format provides the C6.5 molecule with a distinct in vitro and in vivo targeting advantage and has promise as a delivery vehicle for therapeutic agents.