Prolonged in vivo tumour retention of a human diabody targeting the extracellular domain of human HER2/neu.
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.
Adams
G P
GP
Department of Medical Oncology, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
Schier
R
R
McCall
A M
AM
Crawford
R S
RS
Wolf
E J
EJ
Weiner
L M
LM
Marks
J D
JD
D000818:Animals; D000915:Antibody Affinity; D000951:Antigens, Neoplasm / Q000276:immunology*; D019281:Dimerization; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000008:administration & dosage / Q000378:metabolism*; D007147:Immunoglobulin Light Chains / Q000008:administration & dosage / Q000378:metabolism*; D007167:Immunotherapy / Q000379:methods*; D000922:Immunotoxins / Q000008:administration & dosage / Q000378:metabolism*; D051379:Mice; D016513:Mice, SCID; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology*; D014018:Tissue Distribution
D000951:Antigens, Neoplasm; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D000922:Immunotoxins; D018719:Erb-b2 Receptor Tyrosine Kinases