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Ghosh KK, Padmanabhan P, Yang CT, Mishra S, Halldin C, Gulyás B. Dealing with PET radiometabolites. EJNMMI Res 2020; 10:109. [PMID: 32997213 PMCID: PMC7770856 DOI: 10.1186/s13550-020-00692-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Accepted: 09/07/2020] [Indexed: 02/08/2023] Open
Abstract
Abstract Positron emission tomography (PET) offers the study of biochemical,
physiological, and pharmacological functions at a cellular and molecular level.
The performance of a PET study mostly depends on the used radiotracer of
interest. However, the development of a novel PET tracer is very difficult, as
it is required to fulfill a lot of important criteria. PET radiotracers usually
encounter different chemical modifications including redox reaction, hydrolysis,
decarboxylation, and various conjugation processes within living organisms. Due
to this biotransformation, different chemical entities are produced, and the
amount of the parent radiotracer is declined. Consequently, the signal measured
by the PET scanner indicates the entire amount of radioactivity deposited in the
tissue; however, it does not offer any indication about the chemical disposition
of the parent radiotracer itself. From a radiopharmaceutical perspective, it is
necessary to quantify the parent radiotracer’s fraction present in the tissue.
Hence, the identification of radiometabolites of the radiotracers is vital for
PET imaging. There are mainly two reasons for the chemical identification of PET
radiometabolites: firstly, to determine the amount of parent radiotracers in
plasma, and secondly, to rule out (if a radiometabolite enters the brain) or
correct any radiometabolite accumulation in peripheral tissue. Besides,
radiometabolite formations of the tracer might be of concern for the PET study,
as the radiometabolic products may display considerably contrasting distribution
patterns inside the body when compared with the radiotracer itself. Therefore,
necessary information is needed about these biochemical transformations to
understand the distribution of radioactivity throughout the body. Various
published review articles on PET radiometabolites mainly focus on the sample
preparation techniques and recently available technology to improve the
radiometabolite analysis process. This article essentially summarizes the
chemical and structural identity of the radiometabolites of various radiotracers
including [11C]PBB3,
[11C]flumazenil,
[18F]FEPE2I, [11C]PBR28,
[11C]MADAM, and
(+)[18F]flubatine. Besides, the importance of
radiometabolite analysis in PET imaging is also briefly summarized. Moreover,
this review also highlights how a slight chemical modification could reduce the
formation of radiometabolites, which could interfere with the results of PET
imaging. Graphical abstract ![]()
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Affiliation(s)
- Krishna Kanta Ghosh
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore
| | - Parasuraman Padmanabhan
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.
| | - Chang-Tong Yang
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.,Department of Nuclear Medicine and Molecular Imaging, Radiological Sciences Division, Singapore General Hospital, Outram Road, Singapore, 169608, Singapore.,Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Sachin Mishra
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore
| | - Christer Halldin
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.,Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden
| | - Balázs Gulyás
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore. .,Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden.
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Deng H, Konopka CJ, Cross TWL, Swanson KS, Dobrucki LW, Smith AM. Multimodal Nanocarrier Probes Reveal Superior Biodistribution Quantification by Isotopic Analysis over Fluorescence. ACS NANO 2020; 14:509-523. [PMID: 31887006 PMCID: PMC7377915 DOI: 10.1021/acsnano.9b06504] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Absolute measurements of biodistribution are essential for understanding and optimizing the function of nanomaterials for in vivo diagnostic and therapeutic applications. Biodistribution analysis by optical imaging is desirable due to its low cost, wide accessibility, and high-throughput nature, but it is substantially less accurate than isotopic and chemical techniques. In this work, we developed multimodal probes for optical and nuclear imaging to analyze the quantitative limits of optical contrast in the red and near-infrared spectra for polysaccharide nanocarriers targeting macrophage cells. Probes incorporating three zwitterionic fluorophores together with radioactive copper distributed diffusely to optically dissimilar tissues that were either white (visceral adipose tissue) or dark red (liver and spleen) in obese rodents. We used in vivo positron emission tomography/computed tomography (PET/CT) imaging, in vivo hyperspectral tomographic fluorescence imaging, and ex vivo optical and isotopic analyses to determine correlations between optical and nuclear signals. PET imaging strongly correlated with standardized ex vivo methods for all tissue types, whereas no fluorescence signals exhibited substantial accuracy in quantification or localization in vivo. Optical imaging of resected tissues was most accurate in the 700 nm wavelength window, but only in white tissues. This work suggests that fluorescence can be used to measure diffuse probe distribution in white tissues over time or across animals, but not red tissues and not deep in the body. This work also highlights the importance of choosing validated experimental protocols and describes how optical measurements are impacted by fluorophore class and spectral properties, tissue properties, and imaging workflow.
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Affiliation(s)
- Hongping Deng
- Department of Bioengineering, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
- Micro and Nanotechnology Laboratory, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Christian J. Konopka
- Department of Bioengineering, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Tzu-Wen L. Cross
- Division of Nutritional Sciences, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
- Department of Animal Sciences, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Kelly S. Swanson
- Division of Nutritional Sciences, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
- Department of Animal Sciences, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Lawrence W. Dobrucki
- Department of Bioengineering, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
- Cancer Center at Illinois, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
- Carle Illinois College of Medicine, Urbana, Illinois 61801, United States
| | - Andrew M. Smith
- Department of Bioengineering, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
- Micro and Nanotechnology Laboratory, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
- Department of Materials Science and Engineering, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
- Cancer Center at Illinois, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
- Carle Illinois College of Medicine, Urbana, Illinois 61801, United States
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Kalyane D, Raval N, Maheshwari R, Tambe V, Kalia K, Tekade RK. Employment of enhanced permeability and retention effect (EPR): Nanoparticle-based precision tools for targeting of therapeutic and diagnostic agent in cancer. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2019; 98:1252-1276. [PMID: 30813007 DOI: 10.1016/j.msec.2019.01.066] [Citation(s) in RCA: 440] [Impact Index Per Article: 88.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 01/02/2019] [Accepted: 01/15/2019] [Indexed: 02/07/2023]
Abstract
In tumorous tissues, the absence of vasculature supportive tissues intimates the formation of leaky vessels and pores (100 nm to 2 μm in diameter) and the poor lymphatic system offers great opportunity to treat cancer and the phenomenon is known as Enhanced permeability and retention (EPR) effect. The trends in treating cancer by making use of EPR effect is increasing day by day and generate multitudes of possibility to design novel anticancer therapeutics. This review aimed to present various factors affecting the EPR effect along with important things to know about EPR effect such as tumor perfusion, lymphatic function, interstitial penetration, vascular permeability, nanoparticle retention etc. This manuscript expounds the current advances and cross-talks the developments made in the of EPR effect-based therapeutics in cancer therapy along with a transactional view of its current clinical and industrial aspects.
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Affiliation(s)
- Dnyaneshwar Kalyane
- National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, An Institute of National Importance, Government of India, Department of Pharmaceuticals, Ministry of Chemicals and Fertilizers, Palaj, Opposite Air Force Station, Gandhinagar, Gujarat 382355, India
| | - Nidhi Raval
- National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, An Institute of National Importance, Government of India, Department of Pharmaceuticals, Ministry of Chemicals and Fertilizers, Palaj, Opposite Air Force Station, Gandhinagar, Gujarat 382355, India
| | - Rahul Maheshwari
- National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, An Institute of National Importance, Government of India, Department of Pharmaceuticals, Ministry of Chemicals and Fertilizers, Palaj, Opposite Air Force Station, Gandhinagar, Gujarat 382355, India
| | - Vishakha Tambe
- National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, An Institute of National Importance, Government of India, Department of Pharmaceuticals, Ministry of Chemicals and Fertilizers, Palaj, Opposite Air Force Station, Gandhinagar, Gujarat 382355, India
| | - Kiran Kalia
- National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, An Institute of National Importance, Government of India, Department of Pharmaceuticals, Ministry of Chemicals and Fertilizers, Palaj, Opposite Air Force Station, Gandhinagar, Gujarat 382355, India
| | - Rakesh K Tekade
- National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, An Institute of National Importance, Government of India, Department of Pharmaceuticals, Ministry of Chemicals and Fertilizers, Palaj, Opposite Air Force Station, Gandhinagar, Gujarat 382355, India.
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Buckingham F, Gouverneur V. Asymmetric 18F-fluorination for applications in positron emission tomography. Chem Sci 2016; 7:1645-1652. [PMID: 28808536 PMCID: PMC5535067 DOI: 10.1039/c5sc04229a] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 12/12/2015] [Indexed: 01/13/2023] Open
Abstract
Positron emission tomography (PET) is becoming more frequently used by medicinal chemists to facilitate the selection of the most promising lead compounds for further evaluation. For PET, this entails the preparation of 11C- or 18F-labeled drugs or radioligands. With the importance of chirality and fluorine substitution in drug development, chemists can be faced with the challenge of preparing enantiopure molecules featuring the 18F-tag on a stereogenic carbon. Asymmetric 18F-fluorination is an emerging field of research that provides an alternative to resolution or conventional SN2-based radiochemistry. To date, both transition metal complexes and organomediators have been successfully employed for 18F-incorporation at a stereogenic carbon.
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Affiliation(s)
- Faye Buckingham
- University of Oxford , Chemistry Research Laboratory , 12 Mansfield Road , OX1 3UQ , Oxford , UK .
| | - Véronique Gouverneur
- University of Oxford , Chemistry Research Laboratory , 12 Mansfield Road , OX1 3UQ , Oxford , UK .
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Doan BT, Crauste-Manciet S, Bourgaux C, Dhotel H, Jugé L, Brossard D, Scherman D, Bessodes M, Cuenod CA, Mignet N. Lipidic spherulites as magnetic resonance imaging contrast agents. NEW J CHEM 2014. [DOI: 10.1039/c4nj00571f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
There is a need for methods to improve the diagnosis, patient staging and evaluation of therapeutic response in patients with autoimmune conditions to improve patient care. Inflammatory bowel disease (IBD) and rheumatoid arthritis (RA) are two inflammatory diseases characterized by involvement of innate and adaptive immune components that change the metabolic state of their respective target tissues, thus providing an opportunity for molecular imaging probes to detect such changes. Optimally, such probes and the imaging methods employed would be non-invasive, robust and reproducible, give a quantitative result, report on the status of the affected tissue(s) and respond to the effects of a therapeutic molecule. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are nuclear imaging approaches that have the potential to satisfy such requirements. In this review, the work to date and the potential of PET and SPECT imaging probes in these two inflammatory conditions, IBD and RA, are discussed.
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Affiliation(s)
- Helen J McBride
- Inflammation Research, Amgen, Inc., One Amgen Center Drive, MS: 29-1-B, Thousand Oaks, CA 91320, USA.
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7
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Monazzam A, Razifar P, Ide S, Rugaard Jensen M, Josephsson R, Blomqvist C, Langström B, Bergström M. Evaluation of the Hsp90 inhibitor NVP-AUY922 in multicellular tumour spheroids with respect to effects on growth and PET tracer uptake. Nucl Med Biol 2009; 36:335-42. [PMID: 19324279 DOI: 10.1016/j.nucmedbio.2008.12.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2008] [Revised: 12/08/2008] [Accepted: 12/24/2008] [Indexed: 10/21/2022]
Abstract
BACKGROUND Molecular targeting has become a prominent concept in cancer treatment and heat shock protein 90 (Hsp90) inhibitors are suggested as promising anticancer drugs. The Hsp90 complex is one of the chaperones that facilitate the refolding of unfolded or misfolded proteins and plays a role for key oncogenic proteins such as Her2, Raf-1, Akt/PKB, and mutant p53. NVP-AUY922 is a novel low-molecular Hsp90 inhibitor, currently under clinical development as an anticancer drug. Disruption of the Hsp90-client protein complexes leads to proteasome-mediated degradation of client proteins and cell death. The aim of the current study was to use a combination of the multicellular tumour spheroid (MTS) model and positron emission tomography (PET) to investigate the effects of NVP-AUY922 on tumour growth and its relation to PET tracer uptake for the selection of appropriate PET tracer. A further aim was to evaluate the concentration and time dependence in the relation between growth inhibition and PET tracer uptake as part of translational imaging activities. METHODS MTS of two breast cancer cell lines (MCF-7 and BT474), one glioblastoma cell line (U87MG) and one colon carcinoma cell line (HCT116) were prepared. Initially, we investigated MTS growth pattern and (3)H-thymidine incorporation in MTS after continuous exposure to NVP-AUY922 in order to determine dose response. Then the short-term effect of the drug on the four PET tracers 2-[(18)F] fluoro-2-deoxyglucose (FDG), 3'-deoxy-3'-fluorothymidine (FLT), methionine and choline was correlated to the long-term effect (changes in growth pattern) to determine the adequate PET tracer with high predictability. Next, the growth inhibitory effect of different dose schedules was evaluated to determine the optimal dose and time. Finally, the effect of a 2-h exposure to the drug on growth pattern and FDG/FLT uptake was evaluated. RESULTS A dose-dependent inhibition of growth and decrease of (3)H-thymidine uptake was observed with 100% growth cessation in the dose range 7-52 nM and 50% (3)H-thymidine reduction in the range of 10-23 nM, with the most pronounced effect on BT474 cells. The effect of the drug was best detected by FLT. The results suggested that a complete cessation of growth of the viable cell volume was achieved with about 50% inhibition of FLT uptake 3 days after continuous treatment. Significant growth inhibition was observed at all doses and all exposure time spans. Two-hour exposure to NVP-AUY922 generated a growth inhibition which persisted dose dependently up to 10 days. The uptake of FDG per viable tumour volume was reduced by just 25% with 300 nM treatment of the drug, whereas the FLT uptake decreased up to 75% in correlation with the growth inhibition and recovery. CONCLUSIONS Our results indicate a prolonged action of NVP-AUY922 in this cell culture, FLT is a suitable tracer for the monitoring of the effect and a FLT PET study within 3 days after treatment can predict the treatment outcome in this model. If relevant in vivo, this information can be used for efficient planning of animal PET studies and later human PET trial.
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Affiliation(s)
- Azita Monazzam
- Institute of Oncology, Radiology and Clinical Immunology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden.
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8
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Lalich M, McNeel DG, Wilding G, Liu G. Endothelin Receptor Antagonists in Cancer Therapy. Cancer Invest 2009; 25:785-94. [DOI: 10.1080/07357900701522588] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Murphy PS, McCarthy TJ, Dzik-Jurasz ASK. The role of clinical imaging in oncological drug development. Br J Radiol 2008; 81:685-92. [PMID: 18541632 DOI: 10.1259/bjr/16768437] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Clinical imaging has the potential to provide key biomarkers to inform decision-making in drug development. There is considerable optimism that emerging functional imaging techniques will substantially add to the conventional morphological depiction of disease. The discovery, development and qualification of clinical imaging biomarkers remain a considerable undertaking. Once an imaging biomarker is developed, it must be implemented with a high degree of consistency to ensure the collection of robust clinical trial data. The aim of such a development and implementation process is to deliver sufficient confidence in an imaging biomarker to support "go/no-go" decisions made in a drug development programme. This article outlines the drug development process, with a focus on the current impact of clinical imaging on drug development and its probable future direction.
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Affiliation(s)
- P S Murphy
- Pfizer Global Research and Development, Sandwich, Kent, UK.
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Jung KH, Song SH, Paik JY, Koh BH, Choe YS, Lee EJ, Kim BT, Lee KH. Direct Targeting of Tumor Cell F1F0 ATP-Synthase by Radioiodine Angiostatin In Vitro and In Vivo. Cancer Biother Radiopharm 2007; 22:704-12. [DOI: 10.1089/cbr.2007.369] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Kyung-Ho Jung
- Department of Nuclear Medicine, Samsung Medical Center, and Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Sung-Hee Song
- Department of Nuclear Medicine, Samsung Medical Center, and Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Jin-Young Paik
- Department of Nuclear Medicine, Samsung Medical Center, and Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Bong-Ho Koh
- Department of Nuclear Medicine, Samsung Medical Center, and Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Yearn Seong Choe
- Department of Nuclear Medicine, Samsung Medical Center, and Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Eun Jung Lee
- Department of Nuclear Medicine, Samsung Medical Center, and Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Byung-Tae Kim
- Department of Nuclear Medicine, Samsung Medical Center, and Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Kyung-Han Lee
- Department of Nuclear Medicine, Samsung Medical Center, and Sungkyunkwan University School of Medicine, Seoul, Korea
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Abstract
New surrogate end points for monitoring response to cancer treatment are needed for both current and novel therapeutic strategies. Positron emission tomography (PET) as a functional imaging technology provides rapid, reproducible, noninvasive in vivo assessment and quantification of several biological processes targeted by anticancer therapies. PET imaging with F-18 fluorodeoxyglucose (FDG), reflecting tumor glucose metabolism, provides relevant information regarding treatment response. Changes in tumor glucose metabolism precede changes in tumor size and reflect drug effects at a cellular level. FDG-PET enables the prediction of therapy response early in the course as well as determining the viability of residual masses after completion of treatment. The assessment of novel anticancer agents will increasingly depend on functional PET imaging. Assessing responses to new biological drugs using changes in tumor size is likely an inaccurate measure of efficacy. Likewise, monitoring for drug effects using surrogate (nontumor) tissues or serial invasive testing by tumor biopsies does not provide a good correlation with overall antitumor activity. Therefore, the information derived from PET using radiolabeled biological probes provides an alternative approach to conventional structural (anatomical) imaging. PET pharmacokinetic studies will allow for the rapid assessment of novel drug biodistribution, and much smaller patient number studies before decisions on whether or not to proceed with the development of a new drug are made. Summative readouts by PET, such as drug-induced changes in tumor glucose metabolism, tumor cell proliferation and tumor perfusion and, similarly, measures of specific changes will demonstrate whether drugs are having their intended biological effects.
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Affiliation(s)
- Norbert Avril
- Department of Nuclear Medicine, Queen Mary, University of London, Barts & The London School of Medicine, London, EC1A 7BE, UK.
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12
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Abstract
New therapies aimed at molecular abnormalities are often more efficacious and less toxic than nontargeted therapies; however, with current technology, major treatment decisions are being made with inadequate data. This problem needs to be fixed by molecular imaging technology, enabling he noninvasive establishment of the presence of a molecular target, its spatial distribution and heterogeneity, and how this changes over time. This article discusses the status of molecular imaging in clinical trails today, and looks forward to what physicians would like it to become.
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Pawelke B. Metabolite analysis in positron emission tomography studies: examples from food sciences. Amino Acids 2005; 29:377-88. [PMID: 15924213 DOI: 10.1007/s00726-005-0202-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2004] [Accepted: 02/07/2005] [Indexed: 10/25/2022]
Abstract
Substances of various chemical structures can be labelled with appropriate positron emitting isotopes and applied as tracer compounds in PET examinations. Using dynamic data acquisition protocols, time-activity curves of radioactivity uptake in organs can be derived and the measurements of tissue tracer concentrations can be translated into quantitative values of tissue function. However, analysis of metabolites of these tracers regarding their nature and distribution in the living organism is an essential need for the quantitative analysis of PET measurements. In addition, metabolite analysis contributes to the interpretation of the images obtained as well as to the identification of pathological changes in metabolic pathways. This paper reports on representative examples of radiolabelled compounds which might be of importance in food science (e.g., amino acids, polyphenols, and model compounds for advanced glycation end products (AGEs)). Typical procedures of analysis (radio-HPLC, radio-TLC) including pre-analytical sample preparation are described. Specific challenges of the method, e.g., trace amounts of radiolabelled compounds and the influence of the often very short half-lives of positron-emitting nuclides used are highlighted. Representative results of analyses of plasma, urine, and tissue samples are presented and discussed in terms of the metabolic fate of the tracers.
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Affiliation(s)
- B Pawelke
- Positron Emission Tomography Center, Institute of Bioinorganic and Radiopharmaceutical Chemistry, Research Center Rossendorf, Dresden, Germany.
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14
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Abstract
There is a clear need in cancer treatment for a noninvasive imaging assay that evaluates the oxygenation status and heterogeneity of hypoxia and angiogenesis in individual patients. Such an assay could be used to select alternative treatments and to monitor the effects of treatment. Of the several methods available, each imaging procedure has at least one disadvantage. The limited quantitative potential of single-photon emission CT and MR imaging always limits tracer imaging based on these detection systems. PET imaging with FMISO and Cu-ATSM is ready for coordinated multicenter trials, however, that should move aggressively forward to resolve the debate over the importance of hypoxia in limiting response to cancer therapy. Advances in radiation treatment planning, such as intensity-modulated radiotherapy, provide the ability to customize radiation delivery based on physical conformity. With incorporation of regional biologic information, such as hypoxia and proliferating vascular density in treatment planning, imaging can create a biologic profile of the tumor to direct radiation therapy. Presence of widespread hypoxia in the tumor benefits from a systemic hypoxic cell cytotoxin. Angiogenesis is also an important therapeutic target. Imaging hypoxia and angiogenesis complements the efforts in development of antiangiogenesis and hypoxia-targeted drugs. The complementary use of hypoxia and angiogenesis imaging methods should provide the impetus for development and clinical evaluation of novel drugs targeted at angiogenesis and hypoxia. Hypoxia imaging brings in information different from that of FDG-PET but it will play an important niche role in oncologic imaging in the near future. FMISO, radioiodinated azamycin arabinosides, and Cu-ATSM are all being evaluated in patients. The Cu-ATSM images show the best contrast early after injection but these images are confounded by blood flow and their mechanism of localization is one step removed from the intracellular O2 concentration. FMISO has been criticized as inadequate because of its clearance characteristics, but its uptake after 2 hours is probably the most purely reflective of regional PO2 at the time the radiopharmaceutical is used. The FMISO images show less contrast than those of Cu-ATSM because of the lipophilicity and slower clearance of FMISO but attempts to increase the rate of clearance led to tracers whose distribution is contaminated by blood flow effects. For single-photon emission CT the only option is radioiodinated azamycin arabinosides, because the technetium agents are not yet ready for clinical evaluation. Rather than develop new and improved hypoxia agents, or even quibbling about the pros and cons of alternative agents, the nuclear medicine community needs to convince the oncology community that imaging hypoxia is an important procedure that can lead to improved treatment outcome.
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Affiliation(s)
- Joseph G Rajendran
- Division of Nuclear Medicine, Department of Radiology, Box 356113, University of Washington, Seattle, WA 98195, USA.
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Abstract
Positron emission tomography (PET) imaging of small animals enables researchers to bridge the gap between in vitro science and in vivo human studies. The imaging paradigm can be established and refined in animals before implementation in humans and image data related to ex vivo assays of biological activity. Small animal PET (saPET) imaging enables assessment of baseline focal pathophysiology, pharmacokinetics, biological target modulation and the efficacy of novel drugs. The potential and challenge of this technology as applied to anticancer drug development is discussed here.
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Affiliation(s)
- Eric O Aboagye
- Molecular Therapy and PET Oncology Research group, The Clinical Sciences Centre, Faculty of Medicine, Hammersmith Hospital Campus, Imperial College London, Rm. 242 MRC Cyclotron Building, London, W12 0NN, UK.
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MESH Headings
- Animals
- Antibodies, Monoclonal/chemistry
- Antibodies, Monoclonal/pharmacokinetics
- Antibodies, Monoclonal, Humanized
- Benzoquinones
- Bibenzyls/pharmacology
- Diagnostic Imaging/methods
- Diagnostic Imaging/trends
- Down-Regulation
- ErbB Receptors/antagonists & inhibitors
- ErbB Receptors/drug effects
- ErbB Receptors/genetics
- Gefitinib
- HSP90 Heat-Shock Proteins/metabolism
- Heterocyclic Compounds, 1-Ring/chemistry
- Humans
- Lactams, Macrocyclic
- Magnetic Resonance Imaging
- Molecular Probe Techniques
- Mutation
- Neoplasms/drug therapy
- Neoplasms/pathology
- Phthalazines/pharmacology
- Physiological Phenomena/drug effects
- Positron-Emission Tomography/methods
- Protein Binding
- Protein Kinase Inhibitors/pharmacology
- Pyridines/pharmacology
- Quinazolines/pharmacology
- Receptor Protein-Tyrosine Kinases/antagonists & inhibitors
- Receptor Protein-Tyrosine Kinases/drug effects
- Receptor Protein-Tyrosine Kinases/metabolism
- Receptor, ErbB-2/drug effects
- Receptor, ErbB-2/metabolism
- Receptors, Vascular Endothelial Growth Factor/antagonists & inhibitors
- Receptors, Vascular Endothelial Growth Factor/drug effects
- Rifabutin/analogs & derivatives
- Rifabutin/metabolism
- Rifabutin/pharmacology
- Stilbenes/pharmacology
- Tissue Distribution/physiology
- Trastuzumab
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