The long-term objective of this research program is to improve radioimmunotherapy (RIT) for human cancers through the use of antibody-pretargeting strategies. The fundamental hypothesis underlying this work is that optimized single-chain Fv molecule (scFv) based proteins will be ideal vehicles for pre-targeted radioimmunotherapy, since the selective targeting advantages of scFv-based molecules are best seen during the terminal phases of in vivo biodistribution. In the current period of support, the applicant has made substantial progress in identifying the relative contributions of antibody size, valence and binding affinity to quantitative and selective tumor retention in murine models. The C6.5 scFv was isolated from a human phage display library panned against the extracellular domain of HER2/neu, which is an important target in breast cancer and other neoplasms. C6.5 affinity variants were generated using chain-shuffling and site-directed mutagenesis to yield a series of scFv with affinities for HER2/neu ranging from 10(-6) - 10(-11) M. Using these molecules, the applicant has determined that the threshold affinity for detectable in vivo tumor targeting in a murine model is 10(-8) M. Increasing the affinity of scFv to more than 10(-9) M does not further improve quantitative, selective tumor retention. Cumulative targeting selectivity, determined by measuring tumor to normal organ area-under-the-curve ratios, does not exceed that seen with larger IgG molecules, although selective tumor targeting by scFv molecules is substantially better during the terminal phases of biodistribution. Increasing valence has more effect than does affinity on quantitative tumor targeting, even when the results are corrected for antibody size. Divalent scFv exhibit profoundly improved tumor targeting when placed in a diabody format. However, additional improvements are required for effective RIT. The applicant will create an antibody pre-targeted radioimmunotherapy strategy employing scFv fusion proteins targeting HER2/neu and haptens to localize radiometals to tumor sites. This will be accomplished by panning a human scFv phage library to isolate scFv reactive with the chelate, CHX-A."""""""" These scFv will be affinity matured and then fused to the C6.5 diabody to create a bispecific fusion protein that can capture systemically administered 9OYttrium chelated to CHX-A"""""""" and concentrate the radionuclide at tumor sites. Tumor targeting and preclinical radioimmunotherapy studies will be conducted. The advantages of this pretargeting strategy will be sought by also conducting preclinical radioimmunotherapy studies employing the directly conjugated fusion protein or C6.5 IgG1. These studies will identify candidate molecules for clinical development, and will provide a foundation for the clinically effective radioimmunotherapy of solid tumors.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
2R01CA065559-04A1
Application #
6192934
Study Section
Experimental Therapeutics Subcommittee 1 (ET)
Program Officer
Yovandich, Jason L
Project Start
1996-07-01
Project End
2003-06-30
Budget Start
2000-07-01
Budget End
2001-06-30
Support Year
4
Fiscal Year
2000
Total Cost
$353,435
Indirect Cost
Name
Fox Chase Cancer Center
Department
Type
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19111
Adams, Gregory P; Shaller, Calvin C; Dadachova, Ekaterina et al. (2004) A single treatment of yttrium-90-labeled CHX-A""-C6.5 diabody inhibits the growth of established human tumor xenografts in immunodeficient mice. Cancer Res 64:6200-6
Adams, G P; Schier, R; McCall, A M et al. (2001) High affinity restricts the localization and tumor penetration of single-chain fv antibody molecules. Cancer Res 61:4750-5
Powers, D B; Amersdorfer, P; Poul, M et al. (2001) Expression of single-chain Fv-Fc fusions in Pichia pastoris. J Immunol Methods 251:123-35
McCall, A M; Shahied, L; Amoroso, A R et al. (2001) Increasing the affinity for tumor antigen enhances bispecific antibody cytotoxicity. J Immunol 166:6112-7
Adams, G P; Shaller, C C; Chappell, L L et al. (2000) Delivery of the alpha-emitting radioisotope bismuth-213 to solid tumors via single-chain Fv and diabody molecules. Nucl Med Biol 27:339-46
Weiner, L M; Adams, G P (2000) New approaches to antibody therapy. Oncogene 19:6144-51
Nielsen, U B; Adams, G P; Weiner, L M et al. (2000) Targeting of bivalent anti-ErbB2 diabody antibody fragments to tumor cells is independent of the intrinsic antibody affinity. Cancer Res 60:6434-40
McCall, A M; Adams, G P; Amoroso, A R et al. (1999) Isolation and characterization of an anti-CD16 single-chain Fv fragment and construction of an anti-HER2/neu/anti-CD16 bispecific scFv that triggers CD16-dependent tumor cytolysis. Mol Immunol 36:433-45
Adams, G P; Schier, R (1999) Generating improved single-chain Fv molecules for tumor targeting. J Immunol Methods 231:249-60
McCall, A M; Amoroso, A R; Sautes, C et al. (1998) Characterization of anti-mouse Fc gamma RII single-chain Fv fragments derived from human phage display libraries. Immunotechnology 4:71-87

Showing the most recent 10 out of 12 publications