title: Generation and in vivo characterization of a chimeric αvβ5-targeting antibody 14C5 and its derivatives.
abstract: BACKGROUND
  Previous studies showed that radiolabeled murine monoclonal antibody (mAb) 14C5 and its Fab and F(ab')2 fragments, targeting αvβ5 integrin, have promising properties for diagnostic and therapeutic applications in cancer. To diminish the risk of generating a human anti-mouse antibody response in patients, chimeric variants were created. The purpose of this study was to recombinantly produce chimeric antibody (chAb) derivatives of the murine mAb 14C5 and to evaluate the in vitro and in vivo characteristics.
  
  
  METHODS
  In vitro stability, specificity, and affinity of radioiodinated chAb and fragments (Iodo-Gen method) were examined on high-expressing αvβ5 A549 lung tumor cells. In vivo biodistribution and pharmacokinetic characteristics were studied in A549 lung tumor-bearing Swiss Nu/Nu mice.
  
  
  RESULTS
  Saturation binding experiments revealed high in vitro affinity of radioiodinated chAb, F(ab')2, and Fab, with dissociation constants (KD) of 1.19 ± 0.19, 0.68 ± 0.10, and 2.11 ± 0.58 nM, respectively. ChAb 14C5 showed highest tumor uptake (approximately 10%ID/g) at 24 h post injection, corresponding with other high-affinity Abs. ChF(ab')2 and chFab fragments showed faster clearance from the blood compared to the intact Ab.
  
  
  CONCLUSIONS
  The chimerization of mAb 14C5 and its fragments has no or negligible effect on the properties of the antibody. In vitro and in vivo properties show that the chAb 14C5 is promising for radioimmunotherapy, due to its high maximum tumor uptake and its long retention in the tumor. The chF(ab')2 fragment shows a similar receptor affinity and a faster blood clearance, causing less non-specific retention than the chAb. Due to their fast blood clearance, the fragments show high potential for radioimmunodiagnosis.
authors.affiliation: Laboratory of Radiopharmacy, University of Ghent, Harelbekestraat 72, Ghent, 9000, Belgium. Caroline.Dumolyn@UGent.be.
authors.forename: Caroline
authors.initials: C
authors.lastname: Dumolyn
authors.forename: Steve
authors.initials: S
authors.lastname: Schoonooghe
authors.forename: Lieselotte
authors.initials: L
authors.lastname: Moerman
authors.forename: Sara
authors.initials: S
authors.lastname: Neyt
authors.forename: Jurgen
authors.initials: J
authors.lastname: Haustraete
authors.forename: Filip
authors.initials: F
authors.lastname: De Vos
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