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Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2013.

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Molecular Imaging and Contrast Agent Database (MICAD) [Internet].

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125I-T84.66 scFv-human serum albumin

125I-T84.66 scFv-HSA
, PhD
National for Biotechnology Information, NLM, NIH, Bethesda, MD
Corresponding author.

Created: ; Last Update: September 2, 2008.

Chemical name:125I-T84.66 scFv-human serum albumin
Abbreviated name:125I-T84.66 scFv-HSA
Synonym:
Agent category:Antibody fragment
Target:Carcinoembryonic antigen (CEA)
Target category:Antigen
Method of detection:Single-photon emission computed tomography (SPECT), gamma planar imaging
Source of signal:125I
Activation:No
Studies:
  • Checkbox In vitro
  • Checkbox Rodents
Click on protein, nucleotide (RefSeq), and gene for more information about CEA

Background

[PubMed]

Carcinoembryonic antigen (CEA) was first identified from extracts of human colon adenocarcinoma (1) and fetal gut (2). It is a β-glycoprotein, and its predominant expression on the cell surface is increased in a variety of carcinomas and in certain inflammatory conditions such as inflammatory bowel disease (3, 4). CEA has a molecular weight of ~180 kDa, and it can be shed and detected in the serum (5). CEA expression is observed in patients with various carcinomas of the colon, lungs, thyroid, uterus, ovaries, pancreas, and medullary thyroid (6). Radiolabeled monoclonal antibodies (mAbs) have been developed for both the diagnosis and treatment of tumors (7, 8).

Single-chain variable fragments (scFvs) of mAbs with a molecular mass of 25 kDa are cleared very rapidly from the circulation, but they exhibit poor tumor retention because they have a lower affinity than the parent antibody (9). On the other hand, bivalent antibody fragments possess more ideal tumor-targeting characteristics, including rapid tissue penetration, high target retention, and rapid blood clearance. The diabody fragment (a dimer of scFvs; molecular mass = 55 kDa) and the minibody fragment (a dimer of scFvs-CH3 with a linker comprising 18 amino acids; molecular mass = 80 kDa) of a murine/human chimeric anti-CEA T84.66 antibody have been evaluated for targeting in several tumor antigen systems with rapid tumor localization and high-contrast imaging (9, 10). In particular, murine/human chimeric anti-CEA T84.66 diabody and minbody, which retain excellent CEA-binding properties (dissociation constant = 0.01–0.6 nM) (11-13), were developed as CEA imaging agents. However, the pharmacokinetics of radiometal labeled antibodies, with high liver and kidney uptake, are generally not ideal for imaging (14). Albumin is known to accumulate in tumors (15) and has a long blood half-life (16). Furthermore, albumin fusion proteins have been shown to prolong the in vivo circulation of small peptides and proteins (17). A T84.66 single-chain antibody (scFv) was joined with human serum albumin (HSA) using recombinant technology to form T84.66 scFv-albumin fusion protein (T84.66 scFv-HSA), which was radiolabeled with 125I for localization of CEA-positive tumors in mice with single-photon emission computed tomography (SPECT) (18).

Synthesis

[PubMed]

The recombinant T84.66 scFv-HSA (1.2 nmol) was labeled with 44.4 MBq (1.2 mCi) 125I in the presence of Iodogen at room temperature for 10 min (18). 125I-T84.66 scFv-HSA was isolated with size-exclusion chromatography with a radiolabeling efficiency of ~100%. The specific activity was ~37 MBq/nmol (1 mCi/nmol) at the end of purification.

In Vitro Studies: Testing in Cells and Tissues

[PubMed]

Radioimmunoreactivity of 125I-T84.66 scFv-HSA for recombinant CEA was determined to be 81% with high-performance liquid chromatography analysis (18).

Animal Studies

Rodents

[PubMed]

Yazaki et al. (18) performed biodistribution studies of 125I-T84.66 scFv-HSA in nude mice (n = 5 mice/group) with the use of a LS174T human colon carcinoma subcutaneous xenograft model. Data were obtained at 0, 4, 18, 24, 48 and 72 h after injection. Accumulation of the 125I-T84.66 scFv-HSA in the CEA-expressing LS174T tumor was 12.3 ± 1.4% injected dose (ID)/g at 4 h and reached a maximum level of 22.7 ± 6.0% ID/g at 18 h. In comparison, 125I-T84.66 scFv and 125I-HSA reached a maximum of 4.9% ID/g at 0.5 h and 6% ID/g at 4 h, respectively. The liver, heart, spleen, lungs, and kidneys had lower levels of 125I-T84.66 scFv-HSA radioactivity than the LS174T tumor. The rapid blood clearance pattern exhibited a two-phase model with a half-life of 1 h during the distribution phase and a half-life of 15 h during the elimination phase. 125I-T84.66 scFv-HSA exhibited a markedly slower blood clearance than the T84.66 minibody and diabody but cleared faster than the parent T84.66 antibody. SPECT imaging with the 125I-T84.66 scFv-HSA showed high localization to the CEA-positive tumor and relatively low activity elsewhere (except the thyroid) in the mice, confirming the biodistribution data. No blocking experiments were performed.

Other Non-Primate Mammals

[PubMed]

No publication is currently available.

Non-Human Primates

[PubMed]

No publication is currently available.

Human Studies

[PubMed]

References

1.
Gold P., Freedman S.O. Demonstration of tumor-specific antigens in human colonic carcinomata by immunological tolerance and absorption techniques. The Journal of Experimental Medicine. 1964;121:439–462. [PMC free article: PMC2137957] [PubMed: 14270243]
2.
Krupey J., Gold P., Freedman S.O. Purification and characterization of carcinoembryonic antigens of the human digestive system. Nature. 1967;215(5096):67–8. [PubMed: 6053407]
3.
Kowalsky, R.J., and S.W. Falen, Radiopharmaceuticals in nuclear pharmacy and nuclear medicine2004, American Pharmacists Association: Washington, D.C. p. 733-752.
4.
Wahl R.L., Philpott G., Parker C.W. Monoclonal antibody radioimmunodetection of human-derived colon cancer. Invest Radiol. 1983;18(1):58–62. [PubMed: 6832932]
5.
Primus F.J., Freeman J.W., Goldenberg D.M. Immunological heterogeneity of carcinoembryonic antigen: purification from meconium of an antigen related to carcinoembryonic antigen. Cancer Res. 1983;43(2):679–85. [PubMed: 6401222]
6.
Package Insert. CEA-Scan (Arcitumomab) for the preparation of Tc 99m Arcitumomab1999, Immunomedics, Inc. p. 1-15.
7.
Kenanova V., Wu A.M. Tailoring antibodies for radionuclide delivery. Expert Opin Drug Deliv. 2006;3(1):53–70. [PubMed: 16370940]
8.
Wu A.M., Senter P.D. Arming antibodies: prospects and challenges for immunoconjugates. Nat Biotechnol. 2005;23(9):1137–46. [PubMed: 16151407]
9.
Wu A.M., Chen W., Raubitschek A., Williams L.E., Neumaier M., Fischer R., Hu S.Z., Odom-Maryon T., Wong J.Y., Shively J.E. Tumor localization of anti-CEA single-chain Fvs: improved targeting by non-covalent dimers. Immunotechnology. 1996;2(1):21–36. [PubMed: 9373325]
10.
Viti F., Tarli L., Giovannoni L., Zardi L., Neri D. Increased binding affinity and valence of recombinant antibody fragments lead to improved targeting of tumoral angiogenesis. Cancer Res. 1999;59(2):347–52. [PubMed: 9927045]
11.
Fagerstam L.G., Frostell-Karlsson A., Karlsson R., Persson B., Ronnberg I. Biospecific interaction analysis using surface plasmon resonance detection applied to kinetic, binding site and concentration analysis. J Chromatogr. 1992;597(1-2):397–410. [PubMed: 1517343]
12.
Hefta L.J., Neumaier M., Shively J.E. Kinetic and affinity constants of epitope specific anti-carcinoembryonic antigen (CEA) monoclonal antibodies for CEA and engineered CEA domain constructs. Immunotechnology. 1998;4(1):49–57. [PubMed: 9661814]
13.
Williams L.E., Wu A.M., Yazaki P.J., Liu A., Raubitschek A.A., Shively J.E., Wong J.Y. Numerical selection of optimal tumor imaging agents with application to engineered antibodies. Cancer Biother Radiopharm. 2001;16(1):25–35. [PubMed: 11279795]
14.
Yazaki P.J., Wu A.M., Tsai S.W., Williams L.E., Ikler D.N., Wong J.Y., Shively J.E., Raubitschek A.A. Tumor targeting of radiometal labeled anti-CEA recombinant T84.66 diabody and t84.66 minibody: comparison to radioiodinated fragments. Bioconjug Chem. 2001;12(2):220–8. [PubMed: 11312683]
15.
Wang J., Ueno H., Masuko T., Hashimoto Y. Binding of serum albumin on tumor cells and characterization of the albumin binding protein. J Biochem. 1994;115(5):898–903. [PubMed: 7961605]
16.
Dennis M.S., Zhang M., Meng Y.G., Kadkhodayan M., Kirchhofer D., Combs D., Damico L.A. Albumin binding as a general strategy for improving the pharmacokinetics of proteins. J Biol Chem. 2002;277(38):35035–43. [PubMed: 12119302]
17.
Dennis M.S., Jin H., Dugger D., Yang R., McFarland L., Ogasawara A., Williams S., Cole M.J., Ross S., Schwall R. Imaging tumors with an albumin-binding Fab, a novel tumor-targeting agent. Cancer Res. 2007;67(1):254–61. [PubMed: 17210705]
18.
Yazaki P.J., Kassa T., Cheung C.W., Crow D.M., Sherman M.A., Bading J.R., Anderson A.L., Colcher D., Raubitschek A. Biodistribution and tumor imaging of an anti-CEA single-chain antibody-albumin fusion protein. Nucl Med Biol. 2008;35(2):151–8. [PMC free article: PMC3195408] [PubMed: 18312824]

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