Publications by authors named "Joseph Cowell"

5 Publications

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Head-to-head comparison of DFO* and DFO chelators: selection of the best candidate for clinical Zr-immuno-PET.

Eur J Nucl Med Mol Imaging 2021 Mar 5;48(3):694-707. Epub 2020 Sep 5.

Radiology & Nuclear Medicine, Cancer Center Amsterdam, Amsterdam UMC, Vrije Universiteit Amsterdam, De Boelelaan, 1117, Amsterdam, The Netherlands.

Purpose: Almost all radiolabellings of antibodies with Zr currently employ the hexadentate chelator desferrioxamine (DFO). However, DFO can lead to unwanted uptake of Zr in bones due to instability of the resulting metal complex. DFO*-NCS and the squaramide ester of DFO, DFOSq, are novel analogues that gave more stable Zr complexes than DFO in pilot experiments. Here, we directly compare these linker-chelator systems to identify optimal immuno-PET reagents.

Methods: Cetuximab, trastuzumab and B12 (non-binding control antibody) were labelled with Zr via DFO*-NCS, DFOSq, DFO-NCS or DFO*Sq. Stability in vitro was compared at 37 °C in serum (7 days), in formulation solution (24 h ± chelator challenges) and in vivo with N87 and A431 tumour-bearing mice. Finally, to demonstrate the practical benefit of more stable complexation for the accurate detection of bone metastases, [Zr]Zr-DFO*-NCS and [Zr]Zr-DFO-NCS-labelled trastuzumab and B12 were evaluated in a bone metastasis mouse model where BT-474 breast cancer cells were injected intratibially.

Results: [Zr]Zr-DFO*-NCS-trastuzumab and [Zr]Zr-DFO*Sq-trastuzumab showed excellent stability in vitro, superior to their [Zr]Zr-DFO counterparts under all conditions. While tumour uptake was similar for all conjugates, bone uptake was lower for DFO* conjugates. Lower bone uptake for DFO* conjugates was confirmed using a second xenograft model: A431 combined with cetuximab. Finally, in the intratibial BT-474 bone metastasis model, the DFO* conjugates provided superior detection of tumour-specific signal over the DFO conjugates.

Conclusion: DFO*-mAb conjugates provide lower bone uptake than their DFO analogues; thus, DFO* is a superior candidate for preclinical and clinical Zr-immuno-PET.
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http://dx.doi.org/10.1007/s00259-020-05002-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8036225PMC
March 2021

Radiolabelling of the octadentate chelators DFO* and oxoDFO* with zirconium-89 and gallium-68.

J Biol Inorg Chem 2020 08 13;25(5):789-796. Epub 2020 Jul 13.

Ludwig Boltzmann Institute Applied Diagnostics, General Hospital of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria.

In recent years, clinical imaging with zirconium-89 (Zr)-labelled monoclonal antibodies (Ab) by positron emission tomography (immunoPET) has been gaining significant importance in nuclear medicine for the diagnosis of different types of cancer. For complexation of the radiometal Zr and its attachment to the Ab, chelating agents are required. To date, only the hexadentate chelator desferrioxamine (DFO) is applied in the clinic for this purpose. However, there is increasing preclinical evidence that the [Zr]Zr-DFO complex is not sufficiently stable and partly releases the radiometal in vivo due to the incomplete coordination sphere of the metal. This leads to unfavourable unspecific uptake of the osteophilic radiometal in bones, hence decreasing the signal-to-noise-ratio and leading to an increased dose to the patient. In the past, several new chelators with denticities > 6 have been published, notably the octadentate DFO derivative DFO*. DFO*, however, shows limited water solubility, wherefore an oxygen containing analogue, termed oxoDFO*, was developed in 2017. However, no data on the suitability of oxoDFO* for radiolabelling with Zr has yet been reported. In this proof-of-concept study, we present the first radiolabelling results of the octadentate, water-soluble chelator oxoDFO*, as well as the in vitro stability of the resulting complex [Zr]Zr-oxoDFO* in comparison to the analogous octadentate, but less water-soluble derivative DFO* and the current "standard" chelator DFO. In addition, the suitability of DFO* and oxoDFO* for radiolabeling with the short-lived PET metal gallium-68 is discussed. The water-soluble, octadentate chelator oxoDFO* provides stable complexes with the positron emitter Zirconium-89. The radiolabelling can be performed at room temperature and neutral pH and thus, oxoDFO* represents a promising chelator for applications in immunoPET.
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http://dx.doi.org/10.1007/s00775-020-01800-4DOI Listing
August 2020

Synthesis, Characterization, Cytotoxic Activity, and Metabolic Studies of Ruthenium(II) Polypyridyl Complexes Containing Flavonoid Ligands.

Inorg Chem 2020 Apr 19;59(7):4424-4434. Epub 2020 Mar 19.

Chimie ParisTech, PSL University, CNRS, Institute of Chemistry for Life and Health Sciences, Laboratory for Inorganic Chemical Biology, F-75005 Paris, France.

Four novel monocationic Ru(II) polypyridyl complexes were synthesized with the general formula [Ru(DIP)flv]X, where DIP is 4,7-diphenyl-1,10-phenanthroline, flv stands for the flavonoid ligand (5-hydroxyflavone in [Ru(DIP)(5-OHF)](PF), genistein in [Ru(DIP)(gen)](PF), chrysin in [Ru(DIP)(chr)](OTf), and morin in [Ru(DIP)(mor)](OTf)), and X is the counterion, PF, and OTf ̅ (triflate, CFSO̅), respectively. Following the chemical characterization of the complexes by H and C NMR, mass spectrometry, and elemental analysis, their cytotoxicity was tested against several cancer cell lines. The most promising complex, [Ru(DIP)(gen)](PF), was further investigated for its biological activity. Metabolic studies revealed that this complex severely impaired mitochondrial respiration and glycolysis processes, contrary to its precursor, Ru(DIP)Cl, which showed a prominent effect only on the mitochondrial respiration. In addition, its preferential accumulation in MDA-MB-435S cells (a human melanoma cell line previously described as mammary gland/breast; derived from metastatic site: pleural effusion), which are used for the study of metastasis, explained the better activity in this cell line compared to MCF-7 (human, ductal carcinoma).
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http://dx.doi.org/10.1021/acs.inorgchem.9b03562DOI Listing
April 2020

Traceless Cleavage of Protein-Biotin Conjugates under Biologically Compatible Conditions.

Chembiochem 2017 09 19;18(17):1688-1691. Epub 2017 Jul 19.

Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.

Biotinylation of amines is widely used to conjugate biomolecules, but either the resulting label is non-removable or its removal leaves a tag on the molecule of interest, thus affecting downstream processes. We present here a set of reagents (RevAmines) that allow traceless, reversible biotinylation under biologically compatible, mild conditions. Release following avidin-based capture is achieved through the cleavage of a (2-(alkylsulfonyl)ethyl) carbamate linker under mild conditions (200 mm ammonium bicarbonate, pH 8, 16-24 h, room temperature) that regenerates the unmodified amine. The capture and release of biotinylated proteins and peptides from neutravidin, fluorescent labelling through reversible biotinylation at the cell surface and the selective enrichment of proteins from bacterial periplasm are demonstrated. The tags are easily prepared, stable and offer the potential for future application in proteomics, activity-based protein profiling, affinity chromatography and bio-molecule tagging and purification.
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http://dx.doi.org/10.1002/cbic.201700214DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5708275PMC
September 2017

An LC/MS/MS method for stable isotope dilution studies of β-carotene bioavailability, bioconversion, and vitamin A status in humans.

J Lipid Res 2014 Feb 24;55(2):319-28. Epub 2013 Oct 24.

Human Nutrition Research Centre, Newcastle University, Newcastle Upon Tyne, UK.

Isotope dilution is currently the most accurate technique in humans to determine vitamin A status and bioavailability/bioconversion of provitamin A carotenoids such as β-carotene. However, limits of MS detection, coupled with extensive isolation procedures, have hindered investigations of physiologically-relevant doses of stable isotopes in large intervention trials. Here, a sensitive liquid chromatography-tandem mass spectrometry (LC/MS/MS) analytical method was developed to study the plasma response from coadministered oral doses of 2 mg [(13)C10]β-carotene and 1 mg [(13)C10]retinyl acetate in human subjects over a 2 week period. A reverse phase C18 column and binary mobile phase solvent system separated β-carotene, retinol, retinyl acetate, retinyl linoleate, retinyl palmitate/retinyl oleate, and retinyl stearate within a 7 min run time. Selected reaction monitoring of analytes was performed under atmospheric pressure chemical ionization in positive mode at m/z 537→321 and m/z 269→93 for respective [(12)C]β-carotene and [(12)C] retinoids; m/z 547→330 and m/z 274→98 for [(13)C10]β-carotene and [(13)C5] cleavage products; and m/z 279→100 for metabolites of [(13)C10]retinyl acetate. A single one-phase solvent extraction, with no saponification or purification steps, left retinyl esters intact for determination of intestinally-derived retinol in chylomicrons versus retinol from the liver bound to retinol binding protein. Coadministration of [(13)C10]retinyl acetate with [(13)C10]β-carotene not only acts as a reference dose for inter-individual variations in absorption and chylomicron clearance rates, but also allows for simultaneous determination of an individual's vitamin A status.
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http://dx.doi.org/10.1194/jlr.D040204DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3886671PMC
February 2014