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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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64Cu-[cinnamoyl-Phe-D-Leu-Phe-D-Leu-Phe-Lys(PEG-1,4,7,10-Tetraazacyclododecane-N,N’,N’’,N’’’-tetraacetic acid)-NH2]

cFLFLFK-PEG-64Cu

, PhD and , PhD.

Author Information
, PhD
National Center for Biotechnology Information, NLM, NIH, Bethesda, MD 20894, vog.hin.mln.ibcn@dacim
, PhD
University of Virginia, Charlottesville, VA, ude.ainigriv@r3pd

Created: ; Last Update: May 30, 2008.

Chemical name:64Cu-[cinnamoyl-Phe-D-Leu-Phe-D-Leu-Phe-Lys(PEG-1,4,7,10-Tetraazacyclododecane-N,N’,N’’,N’’’-tetraacetic acid)-NH2]
Image cFLFLFK64Cu.jpg
Abbreviated name:cFLFLFK-PEG-64Cu
Synonym:cFLFLF-PEG-64Cu
Agent Category:Compound
Target:N-formylpeptide receptor (FPR)
Target Category:Receptor-ligand binding
Method of detection:Positron emission tomography (PET)
Source of signal:64Cu
Activation:No
Studies:
  • Checkbox Rodents
Structure of cFLFLFK-PEG-64Cu

Background

[PubMed]

White blood cells radiolabeled with indium (as 111In-hexamethylpropyleneamine oxime), technetium (as 99mTc-stannous chloride), or gallium (as 67Ga-citrate) are often used for the detection of infection and inflammation (1). The autologous cells are labeled ex vivo and then reinfused into patients to image the infection or inflammation. Although useful, the use of these radiolabeled cells has some limitations because it requires considerable preparation time and involves the handling of blood, and the labeled leukocytes are not specific for either infection or inflammation. To develop a proper treatment regimen, a careful selection of the tracer (or a combination) has to be made for the detection of the infected or inflamed site (2). As an alternative, various labeled peptides that target specific receptors on infiltrating leukocytes have been investigated for the imaging of infection or inflammation (3, 4). However, although these compounds show promise, they have undesirable side effects because they either activate neutrophils, which results in neutropenia or demargination, have a low retention at the target site, or show low affinity for the receptor (5, 6). Zhang et al. evaluated a neutrophil receptor antagonist, cinnamoyl-phenylalanine-(D) leucine-phenylalanine-(D) leucine-phenylalanine-lysine (cFLFLFK), which had a high affinity for the N-formyl peptide receptor, for the detection of infection, but the investigators observed that it had poor imaging qualities (7). In an effort to improve the imaging quality of cFLFLFK, the investigators modified cFLFLFK by linking the peptide to polyethylene glycol (PEG) and 2,2’,2’’,2’’’-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) (DOTA) to chelate-radiolabeled copper (64Cu) and obtained cFLFLFK-PEG-DOTA-64Cu (FLFLFK-PEG-64Cu). The 64Cu-labeled compound was then evaluated in vivo for the imaging of lung infections in mice (7).

Synthesis

[PubMed]

The synthesis of cFLFLFK-PEG-64Cu was described by Zhang et al. (7). The cFLFLFK peptide was synthesized by Fmol solid-phase chemistry with a peptide synthesizer. Using a procedure modified from that of Chen et al., the peptide was pegylated by mixing it with bifunctional t-butoxycarbonyl (t-Boc)-protected PEG-succinimidyl ester in acetonitrile-sodium borate buffer (pH 8.5) (8). The reaction was allowed to proceed overnight at 4°C, and cFLFLF-PEG was purified by high-performance liquid chromatography (HPLC) with a yield of 62%. Subsequently, t-Boc was cleaved from cFLFLF-PEG by treatment with trifluoroacetic acid. In a separate reaction, DOTA was mixed with N-hydroxysulfosuccinimide (SulfoNHS) and 1-ethyl-3-[3-(diethylamino)-propyl] carbodiimide in water (pH 5.5) at 4°C for 30 min to obtain DOTA-SulfoNHS. The unblocked cFLFLF-PEG was then mixed with DOTA-SulfoNHS in sodium borate buffer (pH 8.5) to obtain cFLFLF-PEG-DOTA.

Radiolabeling of cFLFLF-PEG-DOTA was performed with [64Cu]copper chloride in ammonium acetate buffer (pH 5.5) for 30 min by incubating at 40°C to obtain cFLFLFK-PEG-64Cu. The reaction was terminated by the addition of ethylenediamine tetraacetic acid, and the radiolabeled compound was purified by HPLC on a C18 column. The radiochemical yield and purity of the procedure was reported to be >90%, and the radiochemical had a specific activity of ~30 mCi/μmol (1,110 MBq/ μmol). A cold, non-radioactive version of cFLFLFK-PEG-Cu was also synthesized and used for the HPLC and mass spectroscopic characterization of cFLFLFK-PEG-64Cu.

In Vitro Studies: Testing in Cells and Tissues

[PubMed]

No references are currently available.

Animal Studies

Rodents

[PubMed]

cFLFLFK-PEG-64Cu was evaluated in mice to image bacterial lung infections (7). Pneumonia was induced in the animals by the aspiration of Klebsiella pneumoniae under light inhalation anesthesia. For control animals, sterile saline was used. The animals were administered cFLFLFK-PEG-64Cu through the tail vein 24 h after the bacterial treatment, and positron emission tomography and computed tomography (CT) was performed on the animals 6 h later. The CT images were used to guide the placement of the region of interest (ROI) in the lung and obtain the lung activity concentrations. The standardized uptake values (SUVs) of the tracers were calculated as a ratio of the total ROI uptake concentration normalized to the injected dose and weight of the animal. The SUV of the lungs from the infected animals was determined to be seven-fold higher than that of the control animals. Competition studies with non-radioactive cFLFLFK-PEG-Cu were not reported by the investigators.

Other Non-Primate Mammals

[PubMed]

No references are currently available.

Non-Human Primates

[PubMed]

No references are currently available.

Human Studies

[PubMed]

No references are currently available.

Supplemental Information

[Disclaimers]

NIH Support

Parts of the studies reported in this chapter were supported by NIH grant #s HL-073361 and HD051609

References

1.
Hughes D.K. Nuclear medicine and infection detection: the relative effectiveness of imaging with 111In-oxine-, 99mTc-HMPAO-, and 99mTc-stannous fluoride colloid-labeled leukocytes and with 67Ga-citrate. J Nucl Med Technol. 2003;31(4):196–201. [PubMed: 14657285]
2.
El-Maghraby T.A., Moustafa H.M., Pauwels E.K. Nuclear medicine methods for evaluation of skeletal infection among other diagnostic modalities. Q J Nucl Med Mol Imaging. 2006;50(3):167–92. [PubMed: 16868532]
3.
Babich J.W., Tompkins R.G., Graham W., Barrow S.A., Fischman A.J. Localization of radiolabeled chemotactic peptide at focal sites of Escherichia coli infection in rabbits: evidence for a receptor-specific mechanism. J Nucl Med. 1997;38(8):1316–22. [PubMed: 9255175]
4.
Pollak A., Goodbody A.E., Ballinger J.R., Duncan G.S., Tran L.L., Dunn-Dufault R., Meghji K., Lau F., Andrey T.W., Boxen I., Sumner-Smith M. Imaging inflammation with 99Tcm-labeled chemotactic peptides: analogues with reduced neutropenia. Nucl Med Commun. 1996;17(2):132–9. [PubMed: 8778637]
5.
Lundqvist H., Tolmachev V. Targeting peptides and positron emission tomography. Biopolymers. 2002;66(6):381–92. [PubMed: 12658725]
6.
Rennen H.J., Corstens F.H., Oyen W.J., Boerman O.C. New concepts in infection/inflammation imaging. Q J Nucl Med. 2001;45(2):167–73. [PubMed: 11476166]
7.
Zhang Y., Kundu B., Fairchild K.D., Locke L., Berr S.S., Linden J., Pan D. and , Synthesis of novel neutrophil-specific imaging agents for Positron Emission Tomography (PET) imaging. Bioorg Med Chem Lett. 2007 [PMC free article: PMC2612577] [PubMed: 17959381]
8.
Chen X., Park R., Hou Y., Tohme M., Shahinian A.H., Bading J.R., Conti P.S. microPET and autoradiographic imaging of GRP receptor expression with 64Cu-DOTA-[Lys3]bombesin in human prostate adenocarcinoma xenografts. J Nucl Med. 2004;45(8):1390–7. [PubMed: 15299066]

This MICAD chapter is not included in the Open Access Subset, because it was authored / co-authored by one or more investigators who was not a member of the MICAD staff.

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