Generation and in vivo characterization of a chimeric αvβ5-targeting antibody 14C5 and its derivatives

Abstract

BackgroundPrevious 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.MethodsIn 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.ResultsSaturation 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.ConclusionsThe 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.

Exploration of a F(ab′)2Fragment as the Targeting Agent of α-Radiation Therapy: A Comparison of the Therapeutic Benefit of Intraperitoneal and Intravenous Administered Radioimmunotherapy

“…or i.v., respectively. In the first study, tumor-bearing mice (groups of n = 10) were given increasing doses of 212 Pb-panitumumab F(ab¢) 2 (10,20,30,40,50,60,80, or 100 lCi) by i.p. injection.…”

“…13,15,39 F(ab¢) 2 fragments have been shown to have a faster extravasation rate and localization to tumor, greater penetration of the tumor, and have an overall lower residence time of unbound RIC in the body. [13][14][15]40 With these advantages, the F(ab¢) 2 fragment would be an appropriatetargeting vehicle for i.v. administration of targeted a-radiation.…”

“…The data from the in vitro analysis of the panitumumab F(ab¢) 2 was consistent not only with what has been published for the parental panitumumab IgG, demonstrating that the F(ab¢) 2 fragment has retained the qualities of the intact IgG, but also with other mAb F(ab¢) 2 fragments that have been evaluated for similar applications. 13,15,20,32,40,46,47 The initial in vivo study provided information on the tumor targeting and normal distribution of the panitumumab F(ab¢) 2 when modified with the TCMC chelate and labeled with a Pb(II) isotope. The 203 Pb-panitumumab F(ab¢) 2 was evaluated in the LS-174T i.p.…”