Search tips
Search criteria

Results 1-20 (20)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
author:("cease, bonnie")
1.  Evaluation of Prostate-Specific Membrane Antigen as an Imaging Reporter 
Genetic reporters provide a noninvasive method to monitor and evaluate a population of cells. The ideal properties of a gene reporter-probe system include biocompatibility, lack of immunogenicity, low background expression or signal, and high sensitivity of detection. The prostate-specific membrane antigen (PSMA) is an attractive candidate for a genetic reporter as it is a human trans-membrane protein with a selective expression pattern, and there are several PSMA imaging agents available for clinical and preclinical applications. We evaluated the use of PSMA as a genetic imaging reporter by comparison to 2 clinically established reporters, the mutant herpes simplex virus type I thymidine kinase and the human sodium-iodide symporter.
Adenoviruses expressing each reporter were constructed and validated in vitro for expression and function. To compare PSMA with existing imaging reporters, a bilateral Matrigel suspension model was established with nude mice bearing cells equally infected with each reporter or control adenovirus. Dynamic PET was performed, and time–activity curves were generated for each reporter-probe pair.
A comparison of peak target-to-background ratios revealed that PSMA offered the highest ratio relative to the control Matrigel suspension as well as muscle. Further, as proof of concept, PSMA was applied as an imaging reporter to monitor adenoviral liver transduction with both nuclear and optical imaging probes.
These preliminary studies support further development of PSMA as a noninvasive genetic reporter.
PMCID: PMC4074907  PMID: 24700883
PSMA; molecular-genetic imaging; DCFPyL; positron emission tomography; optical imaging
2.  PET Imaging in Prostate Cancer: Focus on Prostate-Specific Membrane Antigen 
Prostate cancer (PCa) is the second leading cause of cancer-related death in American men. Positron emission tomography/computed tomography (PET/CT) with emerging radiopharmaceuticals promises accurate staging of primary disease, restaging of recurrent disease, detection of metastatic lesions and, ultimately, for predicting the aggressiveness of disease. Prostate-specific membrane antigen (PSMA) is a well-characterized imaging biomarker of PCa. Because PSMA levels are directly related to androgen independence, metastasis and progression, PSMA could prove an important target for the development of new radiopharmaceuticals for PET. Preclinical data for new PSMA-based radiotracers are discussed and include new 89Zr- and 64Cu-labeled anti-PSMA antibodies and antibody fragments, 64Cu-labeled aptamers, and 11C-, 18F-, 68Ga-, 64Cu-, and 86Y-labeled low molecular weight inhibitors of PSMA. Several of these agents, namely 68Ga-HBED-CC conjugate 15, 18F-DCFBC 8, and BAY1075553 are particularly promising, each having detected sites of PCa in initial clinical studies. These early clinical results suggest that PET/CT using PSMA-targeted agents, especially with compounds of low molecular weight, will make valuable contributions to the management of PCa.
PMCID: PMC4067736  PMID: 23590171
DCFBC; molecular imaging; positron emission tomography; PSMA; radiopharmaceutical
3.  Structural Optimization, Biological Evaluation and Application of Peptidomimetic Prostate Specific Antigen Inhibitors 
Journal of medicinal chemistry  2013;56(11):4224-4235.
Prostate-Specific Antigen (PSA) is a serine protease produced at high levels by normal and malignant prostate epithelial cells that is used extensively as a biomarker in the clinical management of prostate cancer. To better understand PSA’s role in prostate cancer progression we prepared a library of peptidyl boronic acid based inhibitors. To enhance selectivity for PSA vs. other serine proteases, we modified the P1 site of the inhibitors to incorporate a bromopropylglycine group. This allowed the inhibitors to participate in halogen bond formation with the serine found at the bottom of the specificity pocket. The best of these Ahx-FSQn(boro)Bpg had PSA Ki of 72 nM and chymotrypsin Ki of 580 nM. In vivo studies using PSA-producing xenografts demonstrated that candidate inhibitors had minimal effect on growth but significantly altered serum levels of PSA. Biodistribution of 125I labeled peptides showed low levels of uptake into tumors compared to other normal tissues.
PMCID: PMC3740768  PMID: 23692593
Prostate cancer; PSA inhibitors; boronic acids; peptidyl-boronic acid; peptidomimetics; serine protease inhibition; chymotrypsin inhibition
4.  Biodistribution, Tumor Detection, and Radiation Dosimetry of 18F-DCFBC, a Low-Molecular-Weight Inhibitor of Prostate-Specific Membrane Antigen, in Patients with Metastatic Prostate Cancer 
Prostate-specific membrane antigen (PSMA) is a type II integral membrane protein expressed on the surface of prostate cancer (PCa) cells, particularly in androgen-independent, advanced, and metastatic disease. Previously, we demonstrated that N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-4-18F-fluorobenzyl-Lcysteine (18F-DCFBC) could image an experimental model of PSMA-positive PCa using PET. Here, we describe the initial clinical experience and radiation dosimetry of 18F-DCFBC in men with metastatic PCa.
Five patients with radiologic evidence of metastatic PCa were studied after the intravenous administration of 370 MBq (10 mCi) of 18F-DCFBC. Serial PET was performed until 2 h after administration. Time- activity curves were generated for selected normal tissues and metastatic foci. Radiation dose estimates were calculated using OLINDA/EXM 1.1.
Most vascular organs demonstrated a slow decrease in radioactivity concentration over time consistent with clearance from the blood pool, with primarily urinary radiotracer excretion. Thirty-two PET-positive suspected metastatic sites were identified, with 21 concordant on both PET and conventional imaging for abnormal findings compatible with metastatic disease. Of the 11 PET-positive sites not identified on conventional imaging, most were within the bone and could be considered suggestive for the detection of early bone metastases, although further validation is needed. The highest mean absorbed dose per unit administered radioactivity (µGy/MBq) was in the bladder wall (32.4), and the resultant effective dose was 19.9 ± 1.34 µSv/MBq (mean ± SD).
Although further studies are needed for validation, our findings demonstrate the potential of 18F-DCFBC as a new positron-emitting imaging agent for the detection of metastatic PCa. This study also provides dose estimates for 18F-DCFBC that are comparable to those of other PET radiopharmaceuticals such as 18F-FDG.
PMCID: PMC3742115  PMID: 23203246
prostate-specific membrane antigen; prostate cancer; 18F; urea; PET/CT
5.  [32P]ATP inhibits the growth of xenografted tumors in nude mice 
Cell Cycle  2012;11(10):1878-1882.
The search for new therapeutic agents that are effective against cancer has been difficult and expensive. The activity of anticancer candidate agents against human cancer-derived cell lines in immunocompromised mice is an important tool in this search. Because ATP is a naturally occurring small molecule, its radiolabeled form poses many advantages as a potential anticancer therapeutic agent. We previously found that a single, low-dose intravenous injection of [32P]ATP inhibited the growth of xenografted tumors in nude mice for up to several weeks. The current study describes the biodistribution and the results and advantages of multi-dose administration of this potential drug. Future studies should investigate the mechanism involved in the possible use of [32P]ATP as a cytotoxic agent that homes naturally to the tumor microenvironment.
PMCID: PMC3359117  PMID: 22544324
mice; tumorinhibition; xenografts; [32P]ATP
7.  2-(3-{1-Carboxy-5-[(6-[18F]fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid, [18F]DCFPyL, a PSMA-based PET Imaging Agent for Prostate Cancer 
We have synthesized and evaluated in vivo 2-(3-{1-carboxy-5-[(6-[18F]fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid, [18F]DCFPyL, as a potential imaging agent for the prostate-specific membrane antigen, PSMA. PSMA is upregulated in prostate cancer epithelia as well as in the neovasculature of most solid tumors.
Experimental Design
[18F]DCFPyL was synthesized in two steps from the p-methoxybenzyl (PMB) protected lys-C(O)-glu urea precursor using 6-[18F]fluoronicotinic acid tetrafluorophenyl ester ([18F]F-Py-TFP) for introduction of 18F. Radiochemical synthesis was followed by biodistribution and imaging with PET in immunocompromised mice using isogenic PC3 PSMA+ and PSMA− xenograft models. Human radiation dosimetry estimates were calculated using OLINDA/EXM 1.0.
DCFPyL displays a Ki value of 1.1 ± 0.1 nM for PSMA. [18F]DCFPyL was produced in radiochemical yields of 36-53% (decay corrected) and specific radioactivities of 340 – 480 Ci/mmol (12.6 – 17.8 GBq/μmol, n = 3). In an immunocompromised mouse model [18F]DCFPyL clearly delineated PSMA+ PC3 PIP prostate tumor xenografts on imaging with PET. At 2 h post-injection, 39.4 ± 5.4 percent injected dose per gram of tissue (%ID/g) was evident within the PIP tumor, with a ratio of 358:1 of uptake within PIP to PSMA− PC3 flu tumor placed in the opposite flank. At or after 1 h post-injection, minimal non-target tissue uptake of [18F]DCFPyL was observed. The bladder wall is the dose-limiting organ.
These data suggest [18F]DCFPyL as a viable, new positron-emitting imaging agent for PSMA-expressing tissues.
PMCID: PMC3243762  PMID: 22042970
PSMA; PET; molecular imaging; prostate cancer; PC3
8.  Novel substrate-based inhibitors of human glutamate carboxypeptidase II with enhanced lipophilicity 
Journal of medicinal chemistry  2011;54(21):7535-7546.
Virtually all low molecular weight inhibitors of human glutamate carboxypeptidase II (GCPII) are highly polar compounds that have limited use in settings where more lipophilic molecules are desired. Here we report the identification and characterization of GCPII inhibitors with enhanced liphophilicity that are derived from a series of newly identified dipeptidic GCPII substrates featuring non-polar aliphatic side chains at the C-terminus. To analyze the interactions governing the substrate recognition by GCPII, we determined crystal structures of the inactive GCPII(E424A) mutant in complex with selected dipeptides and complemented the structural data with quantum mechanics/molecular mechanics calculations. Results reveal the importance of non-polar interactions governing GCPII affinity towards novel substrates as well as formerly unnoticed plasticity of the S1′ specificity pocket. Based on those data, we designed, synthesized and evaluated a series of novel GCPII inhibitors with enhanced lipophilicity, with the best candidates having low nanomolar inhibition constants and clogD > -0.3. Our findings offer new insights into the design of more lipophilic inhibitors targeting GCPII.
PMCID: PMC3222833  PMID: 21923190
PSMA; NAALADase; GCPII; zinc peptidase; folate hydrolase; inhibition; quantum mechanics/molecular mechanics (QM/MM)
10.  High-Throughput Screen Identifies Novel Inhibitors of Cancer Biomarker α-Methylacyl Coenzyme A Racemase (AMACR/P504S) 
Molecular cancer therapeutics  2011;10(5):825-838.
Alpha-methylacyl coenzyme A racemase (AMACR) is a metabolic enzyme whose over-expression has been shown to be a diagnostic indicator of prostatic adenocarcinoma as well as other solid tumors. Here we confirm that attenuation of AMACR expression diminishes the growth of prostate cancer cell lines using stably expressed shRNA constructs. This observation strongly suggests that the AMACR enzyme may be a target for therapeutic inhibition in prostate cancer. To this end, we report here a novel assay capable of screening libraries of diverse small molecules for inhibitors of AMACR activity. This assay facilitated the screening of approximately 5,000 unique compounds and the discovery of seven distinct chemical entities capable of inhibiting AMACR at low micromolar concentrations. The most potent inhibitor discovered is the seleno-organic compound ebselen oxide (IC50:0.80 μM). The parent compound, ebselen (IC50:2.79 μM), is a covalent inactivator of AMACR (KI(inact):24 μM). Two of the AMACR inhibitors appear selectively toxic to prostate cancer cell lines (LAPC4/LNCaP/PC3) that express AMACR compared to a normal prostate fibroblast cell line (WPMY1) that does not express the protein. This report demonstrates the first high-throughput screen for the discovery of novel AMACR inhibitors, characterizes the first non-substrate based inhibitors, and validates that AMACR is a viable chemotherapeutic target in-vitro.
PMCID: PMC3423201  PMID: 21441411
High-Throughput; Inhibitor; AMACR; Prostate Cancer; Racemase; Screen; Assay; Imaging
11.  68Ga-Labeled Inhibitors of Prostate-Specific Membrane antigen (PSMA) for Imaging Prostate Cancer 
Journal of Medicinal Chemistry  2010;53(14):5333-5341.
Gallium-68 is a generator-produced radionuclide for positron emission tomography (PET) that is being increasingly used for radiolabeling of tumor-targeting peptides. Compounds [68Ga]3 and [68Ga]6 are high-affinity, urea-based inhibitors of the prostate-specific membrane antigen (PSMA) that were synthesized in decay-uncorrected yields ranging from 60 – 70% and radiochemical purities of more than 99%. Compound [68Ga]3 demonstrated 3.78 ± 0.90 percent injected dose per gram of tissue (%ID/g) within PSMA+ PIP tumor at 30 min post-injection, while [68Ga]6 showed a two hour PSMA+ PIP tumor uptake value of 3.29 ± 0.77%ID/g. Target (PSMA+ PIP) to non-target (PSMA− flu) ratios were 4.6 and 18.3, respectively, at those time points. Both compounds delineated tumor clearly by small animal PET. The urea series of imaging agents for PSMA can be radiolabeled with 68Ga, a cyclotron-free isotope useful for clinical PET studies, with maintenance of target specificity.
PMCID: PMC3341619  PMID: 20568777
gallium; molecular imaging; positron emission tomography; prostate-specific membrane antigen; radiopharmaceutical
12.  Synthesis and Evaluation of Technetium-99m- and Rhenium-Labeled Inhibitors of the Prostate-Specific Membrane Antigen (PSMA) 
Journal of Medicinal Chemistry  2008;51(15):4504-4517.
The prostate-specific membrane antigen (PSMA) is increasingly recognized as a viable target for imaging and therapy of cancer. We prepared seven 99mTc/Re-labeled compounds by attaching known Tc/Re chelating agents to an amino-functionalized PSMA inhibitor (lys-NHCONH-glu) with or without a variable length linker moiety. Ki values ranged from 0.17 to 199 nM. Ex vivo biodistribution and in vivo imaging demonstrated the degree of specific binding to engineered PSMA+ PC3 PIP tumors. PC3-PIP cells are derived from PC3 that have been transduced with the gene for PSMA. Despite demonstrating nearly the lowest PSMA inhibitory potency of this series, [99mTc(CO)3(L1)]+ (L1 = (2-pyridylmethyl)2N(CH2)4CH(CO2H)-NHCO-(CH2)6CO-NH-lys-NHCONH-glu) showed the highest, most selective PIP tumor uptake, at 7.9 ± 4.0% injected dose per gram of tissue at 30 min postinjection. Radioactivity cleared from nontarget tissues to produce a PIP to flu (PSMA-PC3) ratio of 44:1 at 120 min postinjection. PSMA can accommodate the steric requirements of 99mTc/Re complexes within PSMA inhibitors, the best results achieved with a linker moiety between the ε amine of the urea lysine and the chelator.
PMCID: PMC3336105  PMID: 18637669
13.  A Modular Strategy to Prepare Multivalent Inhibitors of Prostate-Specific Membrane Antigen (PSMA) 
Oncotarget  2011;2(12):1244-1253.
We have developed a modular scaffold for preparing high-affinity, homo-multivalent inhibitors of the prostate-specific membrane antigen (PSMA) for imaging and therapy of prostate cancer (PCa). Our system contains a lysine-based (∝-, ε-) dialkyne residue for incorporating a PSMA binding Lys-Glu urea motif exploiting click chemistry and a second lysine residue for subsequent modification with an imaging or therapeutic moiety. The utility of the multivalent scaffold was examined by synthesizing bivalent compounds 2 and 3 and comparing them with the monovalent analog 1. Determination of inhibition constants (Ki) revealed that bivalent 2 (0.2 nM) and 3 (0.08 nM) are significantly more potent (~ 5 fold and ~ 11 fold, respectively) inhibitors of PSMA than monovalent 1 (0.9 nM). A single photon emission computed tomography (SPECT)-CT imaging study of [111In]3 demonstrated high and specific uptake in PSMA+ PC-3 PIP tumor until at least 48 h post-injection, with rapid clearance from non-target tissues, including kidney. A biodistribution study revealed that [111In]3 demonstrated 34.0 ± 7.5 percent injected dose per gram of tissue in PSMA+ tumor at 24 h post-injection and was capable of generating target-to-non-target ratios of ~ 379 in PSMA+ PC-3 PIP tumors vs. isogenic PSMA-negative PC3-flu tumors in vivo. The click chemistry approach affords a convenient strategy toward multivalent PSMA inhibitors of enhanced affinity and superior pharmacokinetics for imaging.
PMCID: PMC3282081  PMID: 22207391
Prostate-specific membrane antigen (PSMA); NAALADase; bivalent urea inhibitor; molecular imaging; multivalency; SPECT imaging
14.  Improved Syntheses of Precursors for PET Radioligands [18F]XTRA and [18F]AZAN 
Tetrahedron letters  2010;51(40):5333-5335.
Improved syntheses of 7-methyl-2-exo-[3′-(2-bromopyridin-3-yl)-5′-pyridinyl]-7-azabicyclo[2.2.1]heptanes (3) and 7-methyl-2-exo-[3′-(6-bromopyridin-2-yl)-5′-pyridinyl]-7-azabicyclo[2.2.1]heptanes (4), precursors for PET radioligands [18F]XTRA (1) and [18F]AZAN (2), involving a key Stille coupling step followed by deprotection of Boc group and N-methylation are described. The new synthetic procedures provided the title compounds in more than 40% overall yields.
PMCID: PMC2936105  PMID: 20835363
nAChR; PET radioligand; Stille coupling; N-methylation
Bioorganic & medicinal chemistry  2009;17(14):4888-4893.
Prostate-Specific Antigen (PSA) is a serine protease biomarker that may play a role in prostate cancer development and progression. The inhibition of PSA’s enzymatic activity with small molecule inhibitors is an attractive and, as of yet, unexploited target. Previously, we reported a series of peptidyl aldehyde and boronic acid based inhibitors of PSA. In this study, the structural requirements in the P2 and P3 positions of peptide based PSA inhibitors are explored through the substitution of a series of natural and unnatural amino acids in these positions. This analysis demonstrated a preference for hydrophobic residues in the P2 position and amino acids with the potential to hydrogen bond in the P3 position. Using this information, a peptide boronic acid inhibitor with the sequence Cbz-Ser-Ser-Gln-Nle-(boro)-Leu was identified with a Ki for PSA of 25 nM. The attachment of a bulky metal chelating group to the amino terminal of this peptide did not adversely affect PSA inhibition. This result suggests that a platform of PSA-inhibitor chelates could be developed as SPECT or PET-based imaging agents for prostate cancer.
PMCID: PMC3087300  PMID: 19541487
16.  Synthesis and in vivo Evaluation of N-[N-[(S)-1,3-Dicarboxypropyl]carbamoyl]-4-[18F]fluorobenzyl-L-cysteine, [18F]DCFBC: a New Imaging Probe for Prostate Cancer 
Previously we demonstrated successful imaging of xenografts that express the prostate-specific membrane antigen (PSMA) using small animal positron emission tomography (PET) and the radiolabeled PSMA inhibitor N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-S-[11C]methyl-L-cysteine, [11C]DCMC. Herein we extend that work by preparing and testing a PSMA inhibitor of the same class labeled with fluorine-18 to facilitate clinical use.
N-[N-[(S)-1,3-Dicarboxypropyl]carbamoyl]-4-[18F]fluorobenzyl-L-cysteine, [18F]DCFBC was prepared by reacting 4-[18F]fluorobenzyl bromide with the corresponding thiol precursor. SCID mice bearing subcutaneous PSMA+ PC-3 PIP and PSMA- PC-3 FLU tumors were administered [18F]DCFBC via tail vein injection for ex vivo biodistribution and in vivo imaging. For biodistribution, mice were sacrificed and tumor, blood, and major organs were harvested, weighed, and radioactivity was counted. Imaging was performed using small animal PET.
The radiochemical yield for [18F]DCFBC averaged 16 ± 6% (n = 8) from 4-[18F]fluorobenzyl bromide. Specific radioactivities averaged 52 GBq/μmol (1,392 Ci/mmol, n = 6). Biodistribution and imaging studies showed high uptake of [18F]DCFBC in the PIP tumors with little to no uptake in FLU tumors. The maximum PIP tumor uptake was 8.16 ± 2.55 %ID/g, achieved at 60 min after injection, which decreased to 4.69 ± 0.89 at 120 min. The PIP tumor/muscle ratio was 20 at 120 min postinjection. Based on the mouse biodistribution, the dose-limiting organ is kidney (human estimated absorbed dose: 0.05 mGy/MBq; 0.2 rad/mCi).
[18F]DCFBC localizes to PSMA+ expressing tumors in mice, permitting imaging by small animal PET. This new radiopharmaceutical is an attractive candidate for further studies of PET imaging of prostate cancer.
PMCID: PMC3078104  PMID: 18483369
positron emission tomography; prostate-specific membrane antigen; xenograft; PC-3; molecular imaging
17.  Bioisosterism of Urea-Based GCPII Inhibitors: Synthesis and Structure-Activity Relationships Studies 
We report a strategy based on bioisosterism to improve the physicochemical properties of existing hydrophilic, urea-based GCPII inhibitors. Comprehensive structure-activity relationship studies of the P1’ site of ZJ-43- and DCIBzL-based compounds identified several glutamate-free inhibitors with Ki values below 20 nM. Among them, compound 32d (Ki = 11 nM) exhibited selective uptake in GCPII-expressing tumors by SPECT-CT imaging in mice. A novel conformational change of amino acids in the S1’ pharmacophore pocket was observed in the X-ray crystal structure of GCPII complexed with 32d.
PMCID: PMC2818328  PMID: 19897367
PSMA; glutamate carboxypeptidase II; molecular imaging; radiopharmaceutical; SPECT
18.  A Low Molecular Weight PSMA-Based Fluorescent Imaging Agent for Cancer 
We synthesized YC-27 3 to provide a fluorescent imaging probe for the prostate-specific membrane antigen (PSMA), a marker for hormone-independent prostate cancer and tumor neovasculature, with suitable pharmacokinetics for use in vivo. Immediate precursor trifluoroacetate salt of 2-(3-{5-[7-(5-amino-1-carboxy-pentylcarbamoyl)-heptanoylamino]-1-carboxy-pentyl}-ureido)-pentanedioic acid 2 was conjugated with a commercially available near-infrared light emitting dye (IRDye 800CW) to provide 3 in 72% yield. YC-27 3 demonstrated a PSMA inhibitory activity of 0.37 nM and was capable of generating target-to-nontarget ratios of at least 10 in PSMA-expressing PC3-PIP vs. PSMA-negative PC3-flu tumors in vivo. YC-27 3 may be useful for study of PSMA-expressing tissue in preclinical models or for intraoperative guidance.
PMCID: PMC2787846  PMID: 19818734
Prostate-specific membrane antigen; NAALADase; fluorescence; urea; molecular imaging
19.  Synthesis of [125I]IodoDPA-713, a New Probe for Imaging Inflammation 
[125I]IodoDPA-713 [125I]1, which targets the translocator protein (TSPO, 18 KDa), was synthesized in seven steps from methyl-4-methoxybenzoate as a tool for quantification of inflammation in preclinical models. Preliminary in vitro autoradiography and in vivo small animal imaging were performed using [125I]1 in a neurotoxicant-treated rat and in a murine model of lung inflammation, respectively. The radiochemical yield of [125I]1 was 44 ± 6% with a specific radioactivity of 51.8 GBq/μmol (1,400 mCi/μmol) and > 99% radiochemical purity. Preliminary studies showed that [125I]1 demonstrated increased specific binding to TSPO in a neurotoxicant-treated rat and increased radiopharmaceutical uptake in the lungs of an experimental inflammation model of lung inflammation. Compound [125I]1 is a new, convenient probe for preclinical studies of TSPO activity.
PMCID: PMC2764231  PMID: 19703411
pyrazolopyrimidine; peripheral benzodiazepine receptor; translocator protein; autoradiography; small animal imaging
20.  Radiohalogenated Prostate-Specific Membrane Antigen (PSMA)-Based Ureas as Imaging Agents for Prostate Cancer 
Journal of medicinal chemistry  2008;51(24):7933-7943.
To extend our development of new imaging agents targeting the prostate-specific membrane antigen (PSMA), we have used the versatile intermediate 2-[3-(5-amino-1-carboxy-pentyl)-ureido]-pentanedioic acid (Lys-C(O)-Glu), which allows ready incorporation of radiohalogens for single photon emission computed tomography (SPECT) and positron emission tomography (PET). We prepared 2-[3-[1-carboxy-5-(4-[125I]iodo-benzoylamino)-pentyl]-ureido]-pentanedioic acid ([125I]3), 2-[3-[1-carboxy-5-(4-[18F]fluoro-benzoylamino)-pentyl]-ureido]-pentanedioic acid ([18F]6) and 2-(3-[1-carboxy-5-[(5-[125I]iodo-pyridine-3-carbonyl)-amino]-pentyl]-ureido)-pentanedioic acid ([125I]8) in 65 - 80% (non-decay-corrected), 30 - 35% (decay corrected) and 59 - 75% (non-decay-corrected) radiochemical yields. Compound [125I]3 demonstrated 8.8 ± 4.7 percent injected dose per gram (%ID/g) within PSMA+ PC-3 PIP tumor at 30 min postinjection, which persisted, with clear delineation of the tumor by SPECT. Similar tumor uptake values at early time points were demonstrated for [18F]6 (using PET) and [125I]8. Because of the many radiohalogenated moieties that can be attached via the ε amino group, the intermediate Lys-C(O)-Glu is an attractive template upon which to develop new imaging agents for prostate cancer.
PMCID: PMC2631656  PMID: 19053825
NAALADase; GCPII; radiopharmaceutical; SPECT; PET; small animal imaging

Results 1-20 (20)