Biodistribution and planar gamma camera imaging of 123I- and 131I-labeled F(ab′)2 and Fab fragments of monoclonal antibody 14C5 in nude mice bearing an A549 lung tumor

Burvenich, Ingrid J.G.; Schoonooghe, Steve; Blanckaert, Peter; Bacher, Klaus; Vervoort, Liesbet; Coene, Elisabeth; Mertens, Nico; De Vos, Filip; Slegers, Guido

doi:10.1016/j.nucmedbio.2006.12.006

« Previous Next »Nuclear Medicine and Biology
Volume 34, Issue 3 , Pages 257-265, April 2007

Biodistribution and planar gamma camera imaging of ¹²³I- and ¹³¹I-labeled F(ab′)₂ and Fab fragments of monoclonal antibody 14C5 in nude mice bearing an A549 lung tumor

Ingrid J.G. Burvenich
- Laboratory of Radiopharmacy, University of Ghent, B-9000 Ghent, Belgium
- Corresponding author. Tel.: +32 9 2648065; fax: +32 9 2648071.
Steve Schoonooghe
- Department of Biomedical Research, Flanders Institute of Biotechnology (VIB), University of Ghent, B-9000 Ghent, Belgium
Peter Blanckaert
- Laboratory of Radiopharmacy, University of Ghent, B-9000 Ghent, Belgium
Klaus Bacher
- Department of Medical Physics and Radiation Protection, Ghent University, B-9000 Ghent, Belgium
Liesbet Vervoort
- Laboratory of Radiopharmacy, University of Ghent, B-9000 Ghent, Belgium
Elisabeth Coene
- N. Goormaghtigh Institute of Pathology, Ghent University, B-9000 Ghent, Belgium
Nico Mertens
- Department of Biomedical Research, Flanders Institute of Biotechnology (VIB), University of Ghent, B-9000 Ghent, Belgium
Filip De Vos
- Laboratory of Radiopharmacy, University of Ghent, B-9000 Ghent, Belgium
Guido Slegers
- Laboratory of Radiopharmacy, University of Ghent, B-9000 Ghent, Belgium

Received 12 July 2006; received in revised form 6 December 2006; accepted 17 December 2006.

Abstract

Detection of antigen 14C5, involved in substrate adhesion and highly expressed on the membrane of many carcinomas, including lung cancer, provides important diagnostic information that can influence patient management. The aim of this study was to evaluate the biodistribution and planar gamma camera imaging characteristics of radioiodinated F(ab′)₂ and Fab fragments of monoclonal antibody (mAb) 14C5 in tumor-bearing mice.

Methods

F(ab′)₂ and Fab 14C5 fragments were radioiodinated using the Iodo-Gen method. In vitro stability, binding specificity and affinity of ¹²⁵I-labeled 14C5 fragments were studied in A549 lung carcinoma cells. Biodistribution, blood clearance and tumor-targeting characteristics of ¹³¹I-labeled 14C5 fragments and intact mAb 14C5 were studied in Swiss nu/nu mice bearing A549 lung carcinoma tumors. Planar gamma imaging illustrated the potential use of these ¹²³I-labeled 14C5 fragments for radioimmunodetection (RID).

Results

Saturation binding experiments showed highest affinity for ¹²⁵I-labeled F(ab′)₂ fragments (K_d=0.37±0.10 nmol/L) and lowest affinity for ¹²⁵I-labeled Fab fragments (K_d=2.25±0.44 nmol/L). Blood clearance studies showed that the alpha half-life (t½α) value for Fab, F(ab′)₂ and mAb 14C5 was 14.9, 21 and 118 min, respectively. The beta half-life t½β value for Fab, F(ab′)₂ and mAb 14C5 was 439, 627 and 4067 min, respectively. ¹³¹I-Fab fragments showed highest tumor uptake 3 h after injection (2.4±0.8 %ID/g), ¹³¹I-labeled F(ab′)₂ showed highest tumor uptake 6 h after injection (4.7±0.7 %ID/g) and for ¹³¹I-labeled mAb highest tumor uptake was observed at 24 h (10.7±2.3 %ID/g). In planar gamma imaging, both labeled fragments gave better tumor-to-background contrast than ¹²³I-mAb 14C5.

Conclusion

Fab and F(ab′)₂ fragments derived from intact mAb 14C5 have significant potential for diagnostic and therapeutic applications and may provide new tools in mAb-based radiopharmaceuticals for targeting non-small cell lung cancer.

Keywords: Monoclonal antibodies, Radioimmunodetection, Pharmacokinetics, Antibody fragments, mAb 14C5, Lung cancer