26
|
Seidel J, Xi W, Kakareka JW, Pohida TJ, Jagoda EM, Green MV, Choyke PL. Performance characteristics of a positron projection imager for mouse whole-body imaging. Nucl Med Biol 2013; 40:321-30. [PMID: 23402672 DOI: 10.1016/j.nucmedbio.2012.12.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 10/25/2012] [Accepted: 12/01/2012] [Indexed: 10/27/2022]
Abstract
INTRODUCTION We describe a prototype positron projection imager (PPI) for visualizing the whole-body biodistribution of positron-emitting compounds in mouse-size animals. The final version of the PPI will be integrated into the MONICA portable dual-gamma camera system to allow the user to interchangeably image either single photon or positron-emitting compounds in a shared software and hardware environment. METHODS A mouse is placed in the mid-plane between two identical, opposed, pixelated LYSO arrays separated by 21.8-cm and in time coincidence. An image of the distribution of positron decays in the animal is formed on this mid-plane by coincidence events that fall within a small cone angle perpendicular to the two detectors and within a user-specified energy window. We measured the imaging performance of this device with phantoms and in tests performed in mice injected with various compounds labeled with positron-emitting isotopes. RESULTS Representative performance measurements yielded the following results (energy window 250-650keV, cone angle 3.5°): resolution in the image mid-plane, 1.66-mm (FWHM), resolution ±1.5-cm above and below the image plane, 2.2-mm (FWHM), sensitivity: 0.237-cps/kBq (8.76-cps/μCi) (18)F (0.024% absolute). Energy resolution was 15.9% with a linear-count-rate operating range of 0-14.8MBq (0-400μCi) and a corrected sensitivity variation across the field-of-view of <3%. Whole-body distributions of [(18)F] FDG and [(18)F] fluoride were well visualized in mice of typical size. CONCLUSION Performance measurements and field studies indicate that the PPI is well suited to whole-body positron projection imaging of mice. When integrated into the MONICA gamma camera system, the PPI may be particularly useful early in the drug development cycle where, like MONICA, basic whole-body biodistribution data can direct future development of the agent under study and where logistical factors (e.g., available imaging space, non-portability, and cost) may be limitations.
Collapse
|
27
|
Jagoda EM, Lang L, Bhadrasetty V, Histed S, Williams M, Kramer-Marek G, Mena E, Rosenblum L, Marik J, Tinianow JN, Merchant M, Szajek L, Paik C, Cecchi F, Raffensperger K, Jose-Dizon JM, Bottaro DP, Choyke P. Immuno-PET of the hepatocyte growth factor receptor Met using the 1-armed antibody onartuzumab. J Nucl Med 2012; 53:1592-600. [PMID: 22917884 DOI: 10.2967/jnumed.111.102293] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED The overexpression and overactivation of hepatocyte growth factor receptor (Met) in various cancers has been linked to increased proliferation, progression to metastatic disease, and drug resistance. Developing a PET agent to assess Met expression would aid in the diagnosis and monitoring of responses to Met-targeted therapies. In these studies, onartuzumab, the experimental therapeutic 1-armed monoclonal antibody, was radiolabeled with (76)Br or (89)Zr and evaluated as an imaging agent in Met-expressing cell lines and mouse xenografts. METHODS (89)Zr-desferrioxamine (df)-onartuzumab was synthesized using a df-conjugate; (76)Br-onartuzumab was labeled directly. Met-binding studies were performed using the human tumor-derived cell lines MKN-45, SNU-16, and U87-MG, which have relatively high, moderate, and low levels of Met, respectively. Biodistribution and small-animal PET studies were performed in MKN-45 and U87-MG xenografts. RESULTS (76)Br-onartuzumab and (89)Zr-df-onartuzumab exhibited specific, high-affinity Met binding (in the nanomolar range) that was concordant with established Met expression levels. In MKN-45 (gastric carcinoma) xenografts, both tracers cleared slowly from nontarget tissues, with the highest uptake in tumor, blood, kidneys, and lungs. (76)Br-onartuzumab MKN-45 tumor uptake remained relatively constant from 18 h (5 percentage injected dose per gram of tissue [%ID/g]) to 48 h (3 %ID/g) and exhibited tumor-to-muscle ratios ranging from 4:1 to 6:1. In contrast, (89)Zr-df-onartuzumab MKN-45 tumor uptake continued to accumulate from 18 h (10 %ID/g) to 120 h (23 %ID/g), attaining tumor-to-muscle ratios ranging from 20:1 to 27:1. MKN-45 tumors were easily visualized in imaging studies with both tracers at 18 h, but after 48 h (89)Zr-df-onartuzumab image quality improved, with at least 2-fold-greater tumor uptake than nontarget tissues. MKN-45 tumor uptake for both tracers correlated significantly with tumor mass and Met expression and was not affected by the presence of plasma shed Met. CONCLUSION (89)Zr-df-onartuzumab and (76)Br-onartuzumab specifically targeted Met in vitro and in vivo; (89)Zr-df-onartuzumab achieved higher tumor uptake and tumor-to-muscle ratios than (76)Br-onartuzumab at later times, suggesting that (89)Zr-df-onartuzumab would be better suited to image Met for diagnostic and prognostic purposes.
Collapse
|
28
|
Lee YHC, Kiesewetter DO, Lang L, Jagoda EM, Shirani J, Dilsizian V, Eckelman WC. Synthesis of 4-[18F]fluorobenzoyllisinopril: A radioligand for angiotensin converting enzyme (ACE) imaging with positron emission tomography. J Labelled Comp Radiopharm 2012. [DOI: 10.1002/jlcr.2580440194] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
29
|
Jagoda EM, Lang L, McCullough K, Contoreggi C, Kim BM, Ma Y, Rice KC, Szajek LP, Eckelman WC, Kiesewetter DO. [(76) Br]BMK-152, a nonpeptide analogue, with high affinity and low nonspecific binding for the corticotropin-releasing factor type 1 receptor. Synapse 2011; 65:910-8. [PMID: 21308801 DOI: 10.1002/syn.20919] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Accepted: 01/20/2011] [Indexed: 11/07/2022]
Abstract
Corticotropin-releasing factor (CRF), a neuropeptide, regulates endocrine and autonomic responses to stress through G-protein coupled receptors, CRF(1) or CRF(2) . A PET ligand able to monitor changes in CRF(1) receptor occupancy in vivo would aid in understanding the pathophysiology of stress-related diseases as well as in the clinical development of nonpeptide antagonists with therapeutic value. We have radiolabeled the CRF(1) receptor ligand, [8-(4-bromo-2,6-dimethoxyphenyl)-2,7-dimethylpyrazolo[1,5-α][1,3,5]triazin-4-yl]-N,N-bis-(2-methoxyethyl)amine (BMK-152) (ClogP = 2.6), at both the 3 and 4 position with [(76) Br]. Using in vitro autoradiography saturation studies the 4-[(76) Br]BMK-152 exhibited high affinity binding to both rat (K(d) = 0.23 ± 0.07 nM; n = 3) and monkey frontal cortex (K(d) = 0.31 ± 0.08 nM; n = 3) consistent with CRF(1) receptor regional distribution whereas with the 3-[(76) Br]BMK-152, the K(d) s could not be determined due to high nonspecific binding. In vitro autoradiography competition studies using [(125) I]Tyr(0) -o-CRF confirmed that 3-Br-BMK-152 (K(i) = 24.4 ± 4.9 nM; n = 3) had lower affinity (70-fold) than 4-Br-BMK-152 (K(i) = 0.35 ± 0.07 nM; n = 3) in monkey frontal cortex and similiar studies using [(125) I]Sauvagine confirmed CRF(1) receptor selectivity. In vivo studies with P-glycoprotein (PGP) knockout mice (KO) and their wild-type littermates (WT) showed that the brain uptake of 3-[(76) Br]BMK/4-[(76) Br]BMK was increased less than twofold in KO versus WT indicating that 3-[(76) Br]BMK-152/4-[(76) Br]BMK was not a Pgp substrate. Rat brain uptakes of 4-[(76) Br] BMK-152 from ex vivo autoradiography studies showed regional localization consistent with known published CRF(1) receptor distribution and potential as a PET ligand for in vivo imaging of CRF(1) receptors.
Collapse
|
30
|
Ma Y, Lang L, Reyes L, Tokugawa J, Jagoda EM, Kiesewetter DO. Application of highly sensitive UPLC-MS to determine biodistribution at tracer doses: validation with the 5-HT1A ligand [(18)F]FPWAY. Nucl Med Biol 2009; 36:389-93. [PMID: 19423006 PMCID: PMC3644855 DOI: 10.1016/j.nucmedbio.2009.01.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Revised: 12/12/2008] [Accepted: 01/12/2009] [Indexed: 11/30/2022]
Abstract
High-sensitivity and high-resolution LC/MS instrumentation has been applied in positron emission tomography (PET) radiopharmaceutical development to provide quantitative measurement of the mass of radiotracers extracted from tissues of rats. We employed the highly sensitive Waters Q-TOF premier MS coupled with an Acquity UPLC system to demonstrate that LC-MS can generate ex vivo biodistribution data for PET 5-HT(1A) ligand FPWAY without the need to radiolabel. For the biodistribution studies, we injected rats with [(18)F]FPWAY containing various amounts of nonradioactive FPWAY. At the end of the allotted time, the animals were killed and six regions of brain and plasma from each animal were processed for quantitative measurement of parent compound concentration by LC-MS. These data were then converted to the differential uptake ratio DUR (%ID/g*body weight/100) and the brain tissue-specific binding ratio to allow direct comparison with data obtained by gamma counting of the coinjected radioactive [(18)F]FPWAY. The DUR and the brain tissue-specific binding ratio calculated using the LC-MS method were highly correlated to the values obtained by standard radioactivity measurements of [(18)F]FPWAY. In conclusion, there was significant concordance between the LC/MS and radioactivity method in determination of DUR and the specific binding ratio in the rat brain. This concordance indicated that high-sensitivity LC/MS is an indispensable tool in evaluating the quantity of administered chemical in tissue as part of the development of new molecular imaging probes.
Collapse
|
31
|
Kiesewetter DO, Jagoda EM, Shimoji K, Ma Y, Eckelman WC. Evaluation of [18F]fluoroxanomeline {5-{4-[(6-[18F]fluorohexyl)oxy]-1,2,5-thiadiazol-3-yl}-1-methyl-1,2,3,6-tetrahydropyridine} in muscarinic knockout mice. Nucl Med Biol 2007; 34:141-52. [PMID: 17307122 DOI: 10.1016/j.nucmedbio.2006.11.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Revised: 11/17/2006] [Accepted: 11/25/2006] [Indexed: 11/25/2022]
Abstract
INTRODUCTION We set out to develop a muscarinic M1-selective agonist (based on the structure of the functionally M1-selective xanomeline) that could be radiolabeled with fluorine-18 for use as an imaging agent for positron emission tomography. METHODS The radiochemical synthesis was achieved, employing the arts of organic and radiochemical syntheses. Binding selectivity studies employed biodistribution studies, using autoradiography and/or tissue dissection, in wild-type or muscarinic receptor knockout mice. RESULTS [(18)F]Fluoroxanomeline shows rather uniform uptake in all mouse brain regions and high specific binding, with a brain-to-blood ratio of 32 at 60 min postinjection. In addition, the specific binding is demonstrated by a 58% to 75% decrease in brain uptake upon coinjection with 5 nmol of unlabeled fluoroxanomeline or xanomeline. Brain uptake studies with [(3)H]xanomeline in muscarinic knockout mice show decreased uptake in M1 (17-34%) and M2 (2-20%) knockout mice compared with control. However, statistical significance was observed in only a few regions. Comparison of [(18)F]fluoroxanomeline in knockout mice showed no difference in M1 or M4 knockout mice but a general decrease in M2 (2-24%) knockout mice. The decrease of [(18)F]fluoroxanomeline uptake in M2 knockout mice reached statistical significance in brain stem, cerebellum, frontal cortex, hippocampus, inferior colliculus and superior colliculus. CONCLUSION Although xanomeline displays highly selective M1 agonist activity in functional assays, little selectivity for muscarinic subtype binding was observed for xanomeline or its fluorine-containing analogue, fluoroxanomeline. This emphasizes the lack of correlation between functional selectivity and binding selectivity.
Collapse
|
32
|
Dilsizian V, Eckelman WC, Loredo ML, Jagoda EM, Shirani J. Evidence for tissue angiotensin-converting enzyme in explanted hearts of ischemic cardiomyopathy using targeted radiotracer technique. J Nucl Med 2007; 48:182-7. [PMID: 17268012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023] Open
Abstract
UNLABELLED This study aimed to determine the magnitude and distribution of tissue angiotensin-converting enzyme (ACE), mast-cell chymase, and angiotensin II, type 1, plasma membrane receptor (AT1R), in relation to collagen replacement in infarcted and noninfarcted left ventricular myocardial segments. A new radiotracer, 18F-fluorobenzoyl-lisinopril (FBL), was synthesized without compromising its affinity for tissue ACE. METHODS Five- to 10-microm contiguous short-axis slices of explanted hearts from 3 patients with ischemic cardiomyopathy were incubated in vitro with FBL, with and without 10(-6) M lisinopril. Tissue radioactivity was recorded as a function of position in photostimulating luminescence units (PSL). Immunohistochemistry studies were performed with mouse monoclonal antibody against ACE, anti-mast cell chymase, and polyclonal antibody against the human AT1R. RESULTS There was specific binding of FBL to ACE; mean FBL binding was 6.6 +/- 5.2 PSL/mm2, compared with 3.4 +/- 2.5 PSL/mm2 in segments incubated in solution containing cold, 10(-6) M lisinopril (P < 0.0001). Mean FBL binding was 6.3 +/- 4.5 PSL/mm2 in infarcted, 7.6 +/- 4.7 PSL/mm2 in periinfarcted, and 5.0 +/- 1.0 PSL/mm2 in remote, noninfarcted (P < 0.02 vs. periinfarcted) segments. The autoradiographic observations concerning FBL binding were confirmed by ACE and AT1R immunoreactivity. Distribution of mast cell chymase differed from ACE, as a higher number of mast cells was present in the remote, noninfarcted myocardium than in the periinfarcted myocardium (5.1 +/- 3.2 vs. 3.2 +/- 2.2 mast cells per field, P < 0.001). The number of mast cells in ischemic hearts exceeded that in normal hearts (4.2 +/- 2.7 vs. 1.5 +/- 1.2 mast cells per field, x200, P < 0.001). CONCLUSION FBL binds specifically to ACE. The binding is nonuniform in infarcted, periinfarcted, and remote, noninfarcted segments, and there is apparently increased ACE activity in the juxtaposed areas of replacement fibrosis. On the other hand, the distribution of mast cell chymase appears nonuniform and disparate from ACE.
Collapse
|
33
|
Jagoda EM, Lang L, Tokugawa J, Simmons A, Ma Y, Contoreggi C, Kiesewetter D, Eckelman WC. Development of 5-HT1A receptor radioligands to determine receptor density and changes in endogenous 5-HT. Synapse 2006; 59:330-41. [PMID: 16440292 DOI: 10.1002/syn.20246] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
[(18)F]FCWAY and [(18)F]FPWAY, analogues of the high affinity 5-HT(1A) receptor (5-HT(1A)R) antagonist WAY100635, were evaluated in rodents as potential radiopharmaceuticals for determining 5-HT(1A)R density and changes in receptor occupancy due to changes in endogenous serotonin (5-HT) levels. The in vivo hippocampus specific binding ratio [(hippocampus(uptake)/cerebellum(uptake))-1] of [(18)F]FPWAY was decreased to 32% of the ratio of [(18)F]FCWAY, indicating that [(18)F]FPWAY has lower affinity than [(18)F]FCWAY. The 5-HT(1A)R selectivity of [(18)F]FPWAY was confirmed using ex vivo autoradiography studies with 5-HT(1A)R knockout, heterozygous, and wildtype mice.Pre- or post-treatment of awake rodents in tissue dissection studies with paroxetine had no effect on hippocampal binding of [(18)F]FCWAY or [(18)F]FPWAY compared to controls, indicating neither tracer was sensitive to changes in endogenous 5-HT. In mouse ex vivo autoradiography studies in which awake mice were treated with fenfluramine following the [(18)F]FPWAY, a significant decrease was not observed in the hippocampus specific binding ratios. In rat dissection studies with fenfluramine administered following [(18)F]FPWAY or [(18)F]FBWAY ([(18)F]-MPPF) in awake or urethane-anesthetized rats, no significant differences in the specific binding ratios of the hippocampus were observed compared to their respective controls. [(18)F]FPWAY and [(18)F]FBWAY uptakes in all brain regions were increased variably in the anesthetized group (with the greatest increase in the hippocampus) vs. the awake group, but were decreased in the fenfluramine-treated anesthetized group vs. the anesthetized group. These data are best explained by changes in blood flow caused by urethane and fenfluramine, which varies from region to region in the brain.
Collapse
|
34
|
Shirani J, Loredo ML, Eckelman WC, Jagoda EM, Dilsizian V. Imaging the renin-angiotensin-aldosterone system in the heart. Curr Heart Fail Rep 2005; 2:78-86. [PMID: 16036055 DOI: 10.1007/s11897-005-0013-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The influence of the renin-angiotensin system (RAS) is recognized in cardiac and vascular injury. An extrinsic RAS has been known for decades, and an equally important intrinsic RAS has been discovered recently. The latter leads to pathologic tissue alterations in the absence of systemic stimuli and may be the main source of local tissue effects of RAS. A new radiotracer fluorobenzoyl-lisinopril was synthesized by radiolabeling benzoic acid active ester with 18F and reacting that with the epsilon-amino group of lisinopril. The presence of angiotensin-converting enzyme (ACE) activity and angiotensin II receptors was examined in relation to myocardial fibrosis. This tissue-specific radioligand represents the first study of ACE in the human heart. This article presents preliminary data on imaging the RAS in the human cardiac tissue and discusses the potential for clinical application of these imaging techniques to human patients.
Collapse
|
35
|
Jagoda EM, Vaquero JJ, Seidel J, Green MV, Eckelman WC. Experiment assessment of mass effects in the rat: implications for small animal PET imaging. Nucl Med Biol 2005; 31:771-9. [PMID: 15246368 DOI: 10.1016/j.nucmedbio.2004.04.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In vivo imaging using positron emission tomography (PET) is important in the development of new radiopharmaceuticals in rodent animal models for use as biochemical probes, diagnostic agents, or in drug development. We have shown mathematically that, if small animal imaging studies in rodents are to have the same "quality" as human PET studies, the same number of coincidence events must be detected from a typical rodent imaging "voxel" as from the human imaging voxel. To achieve this using the same specific activity preparation, we show that roughly the same total amount of radiopharmaceutical must be given to a rodent as to a human subject. At high specific activities, the mass associated with human doses, when administered to a rodent, may not decrease the uptake of radioactivity at non saturable sites or sites where an enzyme has a high capacity for a substrate. However, in the case of binding sites of low density such as receptors, the increased mass injected could saturate the receptor and lead to physiologic effects and non-linear kinetics. Because of the importance of the mass injected for small animal PET imaging, we experimentally compared high and low mass preparations using ex vivo biodistribution and phosphorimaging of three compounds: 2-fluoro-2-deoxyglucose (FDG), 6-fluoro-L-metatyrosine (FMT) and one receptor-directed compound, the serotonin 5HT1A receptor ligand, trans-4-fluoro-N-[2-[4-(2-methoxylphenyl) piperazino]ethyl]-N-(2-pyridyl) cyclohexane- carboxamide (FCWAY). Changes in the mass injected per rat did not affect the distribution of FDG, FMT, and FCWAY in the range of 0.6-1.9 nmol per rat. Changes in the target to nontarget ratio were observed for injected masses of FCWAY in the range of approximately 5-50 nmol per rat. If the specific activity of such compounds and/or the sensitivity of small animal scanners are not increased relative to human studies, small animal PET imaging will not correctly portray the "true" tracer distribution. These difficulties will only be exacerbated in animals smaller than the rat, e.g., mice.
Collapse
|
36
|
Shimoji K, Esaki T, Itoh Y, Ravasi L, Cook M, Jehle J, Jagoda EM, Kiesewetter DO, Schmidt K, Sokoloff L, Eckelman WC. Inhibition of [18F]FP-TZTP binding by loading doses of muscarinic agonists P-TZTP or FP-TZTP in vivo is not due to agonist-induced reduction in cerebral blood flow. Synapse 2003; 50:151-63. [PMID: 12923818 DOI: 10.1002/syn.10257] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
[(18)F][3-(3-(3-Fluoropropyl)thio)-1,2,5-thiadiazol-4-yl]-1,2,5,6-tetrahydro-1-methylpyridine ([(18)F]FP-TZTP) is an M2 selective muscarinic agonist that may allow noninvasive studies of Alzheimer's disease with PET. 3-(3-(Propylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (P-TZTP), a nonfluorinated analog of FP-TZTP, and unlabeled FP-TZTP inhibited [(18)F]FP-TZTP binding in vivo. Because muscarinic action of the loading dose of P-TZTP administered might have had pharmacological effects, the apparent inhibition might have resulted from reduced delivery rather than competition with receptor-binding. Therefore, we examined the effects of P-TZTP or FP-TZTP administration on cerebral blood flow (CBF) measured by the [(14)C]iodoantipyrine method and laser-Doppler flowmetry in rats. Statistically significant synchronous decreases in both CBF and mean arterial blood pressure (MABP) were observed within the first minute following administration. The decreases in both CBF and MABP were prevented by pretreatment with atropine methyl bromide (M-At), a peripheral muscarinic antagonist, and coadministration of M-At with either FP-TZTP or P-TZTP resulted in the same degree of inhibition of cerebral [(18)F]FP-TZTP-uptake 30 min after administration as observed without M-At. Also, with programmed infusions designed to produce constant arterial concentrations of [(18)F]FP-TZTP and FP-TZTP, which avoid changes in CBF, significant inhibition of [(18)F]FP-TZTP-binding by FP-TZTP was observed. These results indicate that inhibition of [(18)F]FP-TZTP-binding in the brain by P-TZTP or FP-TZTP in vivo occurs independently of their effects on CBF. The methods employed here may also be of interest to evaluate physiological effects of blocking agents utilized to validate other radiopharmaceuticals.
Collapse
|
37
|
Jagoda EM, Aloj L, Seidel J, Lang L, Moody TW, Green S, Caraco C, Daube-Witherspoon M, Green MV, Eckelman WC. Comparison of an 18F labeled derivative of vasoactive intestinal peptide and 2-deoxy-2-[18F]fluoro-D-glucose in nude mice bearing breast cancer xenografts. Mol Imaging Biol 2003; 4:369-79. [PMID: 14537113 DOI: 10.1016/s1536-1632(02)00019-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
PURPOSE A 18fluorine-labeled derivative of vasoactive intestinal peptide [18F- Arg,Arg VIP(18F-dVIP)] was evaluated as a potential imaging agent for breast cancer by comparison with 2-deoxy-2-[18F]fluoro-D-glucose (FDG) using standard ex vivo determinations and small animal position emission tomography (PET) imaging. PROCEDURES Human breast carcinomas, T-47D and MDA-MB231, tumor-bearing nude mice were injected intravenously with 18F-dVIP or FDG for imaging and/or biodistribution (ex vivo) determined by gamma counting. RESULTS FDG had two- to three-fold greater tumor accumulation and target-to-non target contrast relative to 18F-dVIP. VIP receptors were detected in both tumor types but in low concentrations (<15,000 receptors/cell) consistent with lower uptakes. FDG was cleared rapidly from non-target tissues while 18F-dVIP cleared into the kidneys. CONCLUSIONS 18F-dVIP uptake in mice T-47D tumors and kidneys determined by imaging correlated with values determined by ex vivo counting suggesting that tumor and other tissue uptakes can be quantified by in vivo positron projection imaging.
Collapse
|
38
|
Jagoda EM, Kiesewetter DO, Shimoji K, Ravasi L, Yamada M, Gomeza J, Wess J, Eckelman WC. Regional brain uptake of the muscarinic ligand, [18F]FP-TZTP, is greatly decreased in M2 receptor knockout mice but not in M1, M3 and M4 receptor knockout mice. Neuropharmacology 2003; 44:653-61. [PMID: 12668051 DOI: 10.1016/s0028-3908(03)00050-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A muscarinic receptor radioligand, 3-(3-(3-fluoropropyl)thio) -1,2,5,thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (fP-TZTP) radiolabeled with the positron emitting radionuclide (18)F ([(18)F]FP-TZTP) displayed regional brain distribution consistent with M2 receptor densities in rat brain. The purpose of the present study is to further elucidate the subtype selectivity of [(18)F]FP-TZTP using genetically engineered mice which lacked functional M1, M2, M3, or M4 muscarinic receptors. Using ex vivo autoradiography, the regional brain localization of [(18)F]FP-TZTP in M2 knockout (M2 KO) was significantly decreased (51.3 to 61.4%; P<0.01) when compared to the wild-type (WT) mice in amygdala, brain stem, caudate putamen, cerebellum, cortex, hippocampus, hypothalamus, superior colliculus, and thalamus. In similar studies with M1KO, M3KO and M4KO compared to their WT mice, [(18)F]FP-TZTP uptakes in the same brain regions were not significantly decreased at P<0.01. However, in amygdala and hippocampus small decreases of 19.5% and 22.7%, respectively, were observed for M1KO vs WT mice at P<0.05. Given the fact that large decreases in [(18)F]FP-TZTP brain uptakes were seen only in M2 KO vs. WT mice, we conclude that [(18)F]FP-TZTP preferentially labels M2 receptors in vivo.
Collapse
|
39
|
Dilsizian V, Loredo ML, Jagoda EM, Eckelman WC, Shirani J. Scintigraphic and immunohistochemical evidence for localization of angiotensin converting enzyme to myocytes in human ischemic cardiomyopathy. J Am Coll Cardiol 2003. [DOI: 10.1016/s0735-1097(03)81276-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
40
|
Kiesewetter DO, Jagoda EM, Kao CHK, Ma Y, Ravasi L, Shimoji K, Szajek LP, Eckelman WC. Fluoro-, bromo-, and iodopaclitaxel derivatives: synthesis and biological evaluation. Nucl Med Biol 2003; 30:11-24. [PMID: 12493538 DOI: 10.1016/s0969-8051(02)00351-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Paclitaxel (Taxol) is a clinically important chemotherapeutic agent. We describe the synthesis of fluoro-, bromo-, and iodopaclitaxel and their [(18)F]fluoro-, [(76)Br]bromo-, and [(124)I]iodo- analogues. [(18)F]Fluoropaclitaxel shows high uptake and rapid clearance from tissues in rats. Preadministration of paclitaxel in normal rats significantly increases (p < 0.005) retention of [(18)F]fluoropaclitaxel and [(76)Br]bromopaclitaxel in blood (33.0%), heart (32.0%), lung (37.6%) kidney (142.4%); and blood (33.4%), lung (42.3%), kidney (62.4%), respectively. [(18)F]Fluoropaclitaxel uptake in the brain of mdr1a/1b(-/-) mice is increased 1400% (p < 1.3e-07) relative to wild-type controls. Preadministration of paclitaxel or XR9576, a modulator, had little effect on the biodistribution in these mdr1a/1b(-/-) mice. As a result, [(18)F]fluoropaclitaxel will be a useful radiopharmaceutical for the study of multidrug resistant tumors.
Collapse
|
41
|
Zingone A, Seidel J, Aloj L, Caraco C, Vaquero JJ, Jagoda EM, Chou JY, Green MV, Eckelman WC. Monitoring the correction of glycogen storage disease type 1a in a mouse model using [(18)F]FDG and a dedicated animal scanner. Life Sci 2002; 71:1293-301. [PMID: 12106594 DOI: 10.1016/s0024-3205(02)01831-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Monitoring gene therapy of glycogen storage disease type 1a in a mouse model was achieved using [(18)F]FDG and a dedicated animal scanner. The G6Pase knockout (KO) mice were compared to the same mice after infusion with a recombinant adenovirus containing the murine G6Pase gene (Ad-mG6Pase). Serial images of the same mouse before and after therapy were obtained and compared with wild-type (WT) mice of the same strain to determine the uptake and retention of [(18)F]FDG in the liver. Image data were acquired from heart, blood pool and liver for twenty minutes after injection of [(18)F]FDG. The retention of [(18)F]FDG was lower for the WT mice compared to the KO mice. The mice treated with adenovirus-mediated gene therapy had retention similar to that found in age-matched WT mice. These studies show that FDG can be used to monitor the G6Pase concentration in liver of WT mice as compared to G6Pase KO mice. In these mice, gene therapy returned the liver function to that found in age matched WT controls as measured by the FDG kinetics in the liver compared to that found in age matched wild type controls.
Collapse
|
42
|
Kao CHK, Waki A, Sassaman MB, Jagoda EM, Szajek LP, Ravasi L, Shimoji K, Eckelman WC. Evaluation of [76Br]FBAU 3',5'-dibenzoate as a lipophilic prodrug for brain imaging. Nucl Med Biol 2002; 29:527-35. [PMID: 12088722 DOI: 10.1016/s0969-8051(02)00324-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
[76Br]FBAU is a potential PET tracer for assessing proliferation. This study proposes that [76Br]FBAU 3',5'-dibenzoate has higher blood-brain-barrier permeability than [76Br]FBAU itself and thus might be better suited for applications in the brain. The brain uptake indexes of the two compounds measured after carotid injection (29.6 +/- 13.9 for [76Br]FBAU 3',5'-dibenzoate, versus 10.0 +/- 8.7 for [76Br]FBAU) support this claim. Biodistribution study also showed that the brain accumulation of activity was higher in rats injected with [76Br]FBAU 3',5'-dibenzoate than with [76Br]FBAU (0.119+/-0.023 DUR at 1 h, versus 0.061 +/- 0.006). [76Br]FBAU 3',5'-dibenzoate was relatively stable in rat plasma, gradually being hydrolyzed to [76Br]FBAU exponentially with a calculated half-life of 0.8 h. DNA incorporation of [76Br]FBAU was also confirmed. The results presented support the hypothesis that the 3',5'-dibenzoate can act as a prodrug for FBAU and deliver more radiolabeled nucleoside to the brain.
Collapse
|
43
|
Dilsizian V, Loredo M, Ferrans VJ, Jagoda EM, Eckelman WC, Shirani J. Evidence for increased angiotensin II type 1 receptor immunoreactivity in peri-infarct myocardium of human explanted hearts. J Am Coll Cardiol 2002. [DOI: 10.1016/s0735-1097(02)81639-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
44
|
Ma Y, Kiesewetter DO, Jagoda EM, Huang BX, Eckelman WC. Identification of metabolites of fluorine-18-labeled M2 muscarinic receptor agonist, 3-(3-[(3-fluoropropyl)thio]-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine, produced by human and rat hepatocytes. J Chromatogr B Analyt Technol Biomed Life Sci 2002; 766:319-29. [PMID: 11824820 DOI: 10.1016/s0378-4347(01)00517-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
An accurate, rapid method for the determination of unmetabolized 3-(3-[(3-[18F]fluoropropyl)thio]-1,2,5-thiadiazol-4-yl)-1.2,5,6-tetrahydro-1-methylpyridine (FP-TZTP), a selective M2 muscarinic agonist, is necessary in order to obtain quantitative information from positron emission tomography (PET) imaging. Using LC-MS-MS to analyze products from cultured human and rat hepatocytes, we identified metabolites resulting from oxidation of the nitrogen in the tetrahydropyridine ring, sulfur-oxidation, demethylation of the tertiary amine, and oxidation of the tetrahydropyridine ring. From the knowledge of the structure of the metabolites, we have developed a two-step extraction sequence that allows rapid determination of the parent fraction in plasma without time-consuming chromatographic analysis.
Collapse
|
45
|
Kiesewetter DO, Jagoda EM, Starrett JE, Gribkoff VK, Hewawasam P, Srinivas N, Salazar D, Eckelman WC. Radiochemical synthesis and biodistribution of a novel maxi-K potassium channel opener. Nucl Med Biol 2002; 29:55-9. [PMID: 11786276 DOI: 10.1016/s0969-8051(01)00281-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The racemate 1, ((+/-)-(5-Chloro-2-methoxyphenyl)-1,3-dihydro-3-fluoro-6-(trifluoromethyl)- 2H-indol-2-one), is a potent, specific and novel opener of cloned large-conductance, calcium-activated (maxi-K) potassium channels. One of its enantiomers, BMS-204352 (MaxiPost), is undergoing clinical evaluation for efficacy in patients with suspected acute stroke. In the current study, we have prepared [(18)F]-labeled 1 using a silver assisted nucleophilic substitution to examine its distribution and disposition in the rat, with particular emphasis on the brain. Biodistribution studies in rats confirm that brain uptake is rapid and occurs at high levels, and indicate that a major fraction of the compound in the brain does not accumulate by a specific, saturable mechanism.
Collapse
|
46
|
Kiesewetter DO, Sassaman MB, Robbins J, Jagoda EM, Carson RE, Appel NM, Sutkowski E, Herscovitch P, Braun A, Eckelman WC. Synthesis and evaluation of an 18F analog of forskolin for imaging adenylyl cyclase. J Fluor Chem 2000. [DOI: 10.1016/s0022-1139(99)00174-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
47
|
Magata Y, Lang L, Kiesewetter DO, Jagoda EM, Channing MA, Eckelman WC. Biologically stable [(18)F]-labeled benzylfluoride derivatives. Nucl Med Biol 2000; 27:163-8. [PMID: 10773545 DOI: 10.1016/s0969-8051(99)00108-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Use of the [(18)F]-fluoromethyl phenyl group is an attractive alternative to direct fluorination of phenyl groups because the fluorination of the methyl group takes place under milder reaction conditions. However, we have found that 4-FMeBWAY showed femur uptake equal to that of fluoride up to 30 min in rat whereas 4-FMeQNB had a significantly lower percent injected dose per gram in femur up to 120 min. For these and other benzylfluoride derivatives, there was no clear in vivo structure-defluorination relationship. Because benzylchlorides (BzCls) are known alkylating agents, benzylfluorides may be alkylating agents as well, which may be the mechanism of defluorination. On this basis, the effects of substitution on chemical stability were evaluated by the 4-(4-nitro-benzyl)-pyridine (NBP) test, which is used to estimate alkylating activity with NBP. The effect of substitution on the alkylating activity was evaluated for nine BzCl derivatives: BzCl; 3- or 4-methoxy (electron donation) substituted BzCl; 2-, 3-, or 4-nitro (electron withdrawing) substituted BzCl; and 2-, 3-, or 4-chloro (electron withdrawing) substituted BzCl. Taken together, the alkylating reactivity of 3-chloro-BzCl was the weakest. This result was then applied to [(18)F]-benzylfluoride derivatives and in vivo and in vitro stability were evaluated. Consequently, 3-chloro-[(18)F]-benzylfluoride showed a 70-80% decrease of defluorination in both experiments in comparison with [(18)F]-benzylfluoride, as expected. Moreover, a good linear relationship between in vivo femur uptake and in vitro hepatocyte metabolism was observed with seven (18)F-labeled radiopharmaceuticals, which were benzylfluorides, alkylfluorides, and arylfluorides. Apparently, the [(18)F]-fluoride ion is released by metabolism in the liver in vivo. In conclusion, 3-chloro substituted BzCls are the most stable, which suggests that 3-chloro benzylfluorides will be the most chemically stable compound. This result should be important in future design of radioligands labeled with a benzylfluoride moiety.
Collapse
|
48
|
Kiesewetter DO, Carson RE, Jagoda EM, Herscovitch P, Eckelman WC. Using single photon emission tomography (SPECT) and positron emission tomography (PET) to trace the distribution of muscarinic acetylcholine receptor (MACHR) binding radioligands. Life Sci 1999; 64:511-8. [PMID: 10069517 DOI: 10.1016/s0024-3205(98)00595-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Two [18F] labeled ligands for the mAChR were prepared and evaluated in rodents and nonhuman primates. The properties of both compounds, one an agonist and the other an antagonist, were consistent with M2 subtype specificity.
Collapse
|
49
|
Kiesewetter DO, Carson RE, Jagoda EM, Herscovitch P, Eckelman WC. In vivo muscarinic binding of 3-(alkylthio)-3-thiadiazolyl tetrahydropyridines. Synapse 1999; 31:29-40. [PMID: 10025681 DOI: 10.1002/(sici)1098-2396(199901)31:1<29::aid-syn5>3.0.co;2-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Based on encouraging in vitro data indicating M2 subtype selectivity, we synthesized, radiolabeled with 18F, and evaluated 3-(3-(2-fluoroethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetr ahydro-1-methylpyridine [FE-TZTP], and 3-(3-(3-fluoropropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tet rahydro-1-methylpyridine [FP-TZTP] for muscarinic subtype selectivity in vivo. [18F]FE-TZTP displays high uptake in vivo but is inhibited only weakly by coinjecting unlabeled P-TZTP. Contrarily, [18F]FP-TZTP shows significant inhibition of uptake by coinjecting unlabeled P-TZTP or the muscarinic agonist L-687,306 (3-(3-cyclopropyl-1,2,4-oxadiazol-5-yl)-1-azabicyclo[2.2.1]heptane ). Using in vivo autoradiography, [18F]FP-TZTP displays regional distribution consistent with M2 subtype distribution. In addition, [18F]FP-TZTP shows specific uptake in the heart at 5 min. Analysis of metabolites in the awake rat brain revealed that the parent compound represents >95% of the extractable activity at 30 min. In vivo studies in rhesus monkeys revealed rapid brain uptake of [18F]FP-TZTP, with clearance sustained over 2 h. Administration of P-TZTP or FP-TZTP (80 nmol/kg) at 60 min after injection of [18F]FP-TZTP results in a significant displacement of brain activity in all regions. Metabolite analysis in monkey plasma shows that parent compound represents 20% of the extractable radioactivity at 40 min postinjection. One metabolite, which increases with time, has similar lipophilicity to the parent. However, based on metabolism in rat we believe metabolites are not in the brain to any significant extent in monkeys during the time of imaging studies. Regional uptake, autoradiographic distribution, and clearance rates in the brain are consistent with the hypothesis that [18F]FP-TZTP is M2 selective in vivo.
Collapse
|
50
|
Kiesewetter DO, Carson RE, Jagoda EM, Endres CJ, Der MG, Herscovitch P, Eckelman WC. In vivo muscarinic binding selectivity of (R,S)- and (R,R)-[18F]-fluoromethyl QNB. Bioorg Med Chem 1997; 5:1555-67. [PMID: 9313861 DOI: 10.1016/s0968-0896(97)00100-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have developed a multistep radiochemical synthesis of two diastereomers of quinuclidinyl-4-[18F]-fluoromethyl-benzilate ([18F]-FMeQNB), a high-affinity ligand for muscarinic acetylcholine receptors. Previously, we have shown that the nonradioactive (R,R)-diastereomer displays an eightfold selectivity for M1 over M2 while the nonradioactive (R,S)-diastereomer displays a sevenfold selectivity for M2 over M1 in vitro. This paper reports the results of in vivo comparison studies. In the rat, uptake of (R,S)-[18F]-FMeQNB was nearly uniform in all brain regions following the concentration of M2 subtype. The uptake was reduced by 36-54% in all brain regions on coinjection with 50 nmol of unlabeled ligand. An injection of (R,S)-[18F]-FMeQNB followed at 60 min by injection of unlabeled ligand and subsequent sacrifice at 120 min displaced 30-50% of radioactivity in the pons, medulla, and cerebellum, which contain a high proportion of M2 subtype. The most dramatic displacement and inhibition of uptake on coinjection of (R,S)-[18F]-FMeQNB was observed in the heart. In rhesus monkey, the compound showed prolonged uptake and retention in the brain. In the blood, the parent compound degraded rapidly to a single radiolabeled polar metabolite believed to be fluoride. Within 30 min the parent compound represented less than 5% of the plasma activity. Displacement with (R)-QNB was generally slow, but was more rapid from those tissues which contain a higher proportion of M2 subtype. The results are consistent with the hypothesis that (R,S)-[18F]-FMeQNB is M2 selective in vivo. On the other hand, (R,R)-[18F]-FMeQNB showed higher uptake in those brain regions containing a higher concentration of M1 subtype. Uptake in the heart at 60 min was much lower than that observed with the (R,S)-diastereomer. Inhibition of uptake on coinjection with unlabeled (R,S)-FMeQNB is only significant in the heart, thalamus, and pons. Inhibition of uptake on coinjection with unlabeled (R,R)-FMeQNB is quite uniform in all brain regions. Displacement with (R)-QNB shows a more varying amount displaced. These results are consistent with (R,R)-[18F]-FMeQNB being M1 selective in vivo.
Collapse
|