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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.

ABSTRACT: We have synthesized and evaluated in vivo 2-(3-{1-carboxy-5-[(6-[(18)F]fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid, [(18)F]DCFPyL, as a potential imaging agent for the prostate-specific membrane antigen (PSMA). PSMA is upregulated in prostate cancer epithelia and in the neovasculature of most solid tumors.[(18)F]DCFPyL was synthesized in two steps from the p-methoxybenzyl (PMB) protected lys-C(O)-glu urea precursor using 6-[(18)F]fluoronicotinic acid tetrafluorophenyl ester ([(18)F]F-Py-TFP) for introduction of (18)F. Radiochemical synthesis was followed by biodistribution and imaging with PET in immunocompromised mice using isogenic PSMA PC3 PIP and PSMA- PC3 flu xenograft models. Human radiation dosimetry estimates were calculated using OLINDA/EXM 1.0.DCFPyL displays a K(i) value of 1.1 ± 0.1 nmol/L for PSMA. [(18)F]DCFPyL was produced in radiochemical yields of 36%-53% (decay corrected) and specific radioactivities of 340-480 Ci/mmol (12.6-17.8 GBq/?mol, n = 3). In an immunocompromised mouse model [(18)F]DCFPyL clearly delineated PSMA+ PC3 PIP prostate tumor xenografts on imaging with PET. At 2 hours postinjection, 39.4 ± 5.4 percent injected dose per gram of tissue (%ID/g) was evident within the PSMA+ PC3 PIP tumor, with a ratio of 358:1 of uptake within PSMA+ PC3 PIP to PSMA- PC3 flu tumor placed in the opposite flank. At or after 1 hour postinjection, minimal nontarget tissue uptake of [(18)F]DCFPyL was observed. The bladder wall is the dose-limiting organ.These data suggest [(18)F]DCFPyL as a viable, new positron-emitting imaging agent for PSMA-expressing tissues.

SUBMITTER: Chen Y

PROVIDER: S-EPMC3243762 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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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.

Chen Ying Y Pullambhatla Mrudula M Foss Catherine A CA Byun Youngjoo Y Nimmagadda Sridhar S Senthamizhchelvan Srinivasan S Sgouros George G Mease Ronnie C RC Pomper Martin G MG

Clinical cancer research : an official journal of the American Association for Cancer Research 20111031 24

<h4>Purpose</h4>We have synthesized and evaluated in vivo 2-(3-{1-carboxy-5-[(6-[(18)F]fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid, [(18)F]DCFPyL, as a potential imaging agent for the prostate-specific membrane antigen (PSMA). PSMA is upregulated in prostate cancer epithelia and in the neovasculature of most solid tumors.<h4>Experimental design</h4>[(18)F]DCFPyL was synthesized in two steps from the p-methoxybenzyl (PMB) protected lys-C(O)-glu urea precursor using 6-[(18 ...[more]

PMID: 22042970

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Project description:Alpha-particle emitters have a high linear energy transfer and short range, offering the potential for treating micrometastases while sparing normal tissues. We developed a urea-based, 211At-labeled small molecule targeting prostate-specific membrane antigen (PSMA) for the treatment of micrometastases due to prostate cancer (PC).MethodsPSMA-targeted (2S)-2-(3-(1-carboxy-5-(4-211At-astatobenzamido)pentyl)ureido)-pentanedioic acid (211At- 6: ) was synthesized. Cellular uptake and clonogenic survival were tested in PSMA-positive (PSMA+) PC3 PIP and PSMA-negative (PSMA-) PC3 flu human PC cells after 211At- 6: treatment. The antitumor efficacy of 211At- 6: was evaluated in mice bearing PSMA+ PC3 PIP and PSMA- PC3 flu flank xenografts at a 740-kBq dose and in mice bearing PSMA+, luciferase-expressing PC3-ML micrometastases. Biodistribution was determined in mice bearing PSMA+ PC3 PIP and PSMA- PC3 flu flank xenografts. Suborgan distribution was evaluated using ?-camera images, and microscale dosimetry was modeled. Long-term toxicity was assessed in mice for 12 mo.Results211At- 6: treatment resulted in PSMA-specific cellular uptake and decreased clonogenic survival in PSMA+ PC3 PIP cells and caused significant tumor growth delay in PSMA+ PC3 PIP flank tumors. Significantly improved survival was achieved in the newly developed PSMA+ micrometastatic PC model. Biodistribution showed uptake of 211At- 6: in PSMA+ PC3 PIP tumors and in kidneys. Microscale kidney dosimetry based on ?-camera images and a nephron model revealed hot spots in the proximal renal tubules. Long-term toxicity studies confirmed that the dose-limiting toxicity was late radiation nephropathy.ConclusionPSMA-targeted 211At- 6: ?-particle radiotherapy yielded significantly improved survival in mice bearing PC micrometastases after systemic administration. 211At- 6: also showed uptake in renal proximal tubules resulting in late nephrotoxicity, highlighting the importance of long-term toxicity studies and microscale dosimetry.

Project description:BACKGROUND:Due to its high and consistent expression in prostate cancer (PCa), the prostate-specific membrane antigen (PSMA) represents an ideal target for molecular imaging and targeted therapy using highly specific radiolabeled PSMA ligands. To address the continuously growing clinical demand for 18F-labeled PSMA-probes, we developed two novel Glu-urea-Glu-(EuE)-based inhibitors, EuE-k-18F-FBOA (1) and EuE-k-?-a-18F-FPyl (2), both with optimized linker structure and different 18F-labeled aromatic moieties. The inhibitors were evaluated in a comparative preclinical study with 18F-DCFPyl and 18F-PSMA-1007. RESULTS:Radiolabeling procedures allowed preparation of (1) and (2) with high radiochemical yields (67?±?7 and 53?±?7%, d.c.) and purity (>?98%). When compared with 18F-DCFPyl (IC50 = 12.3?±?1.2 nM) and 18F-PSMA-1007 (IC50 = 4.2?±?0.5 nM), both metabolically stable EuE-based ligands showed commensurable or higher PSMA affinity (IC50 = 4.2?±?0.4 nM (1), IC50 = 1.1?±?0.2 nM (2)). Moreover, 1.4- and 2.7-fold higher internalization rates were observed for (1) and (2), respectively, resulting in markedly enhanced tumor accumulation in LNCaP-tumor-bearing mice ((1) 12.7?±?2.0% IA/g, (2) 13.0°?±?1.0% IA/g vs. 7.3?±?1.0% IA/g (18F-DCFPyl), 7.1?±?1.5% IA/g (18F-PSMA-1007), 1 h p.i.). In contrast to (1), (2) showed higher kidney accumulation and delayed clearance kinetics. Due to the high hydrophilicity of both compounds, almost no unspecific uptake in non-target tissue was observed. In contrast, due to the less hydrophilic character (logP?=?-?1.6) and high plasma protein binding (98%), 18F-PSMA-1007 showed uptake in non-target tissue and predominantly hepatobiliary excretion, whereas, 18F-DCFPyl exhibited pharmacokinetics quite similar to those obtained with (1) and (2). CONCLUSION:Both 18F-labeled EuE-based PSMA ligands showed excellent in vitro and in vivo PSMA-targeting characteristics. The substantially higher tumor accumulation in mice compared to recently introduced 18F-PSMA-1007 and 18F-DCFPyl suggests their high value for preclinical studies investigating the effects on PSMA-expression. In contrast to (2), (1) seems to be more promising for further investigation, due to the more reliable 18F-labeling procedure, the faster clearance kinetics with comparable high tumor uptake, resulting therefore in better high-contrast microPET imaging as early as 1 h p.i.

Project description:BACKGROUND:Recent studies reported on high uptake of the PSMA ligands [68Ga]HBED-CC (68Ga-PSMA) and 18F-DCFPyL in cerebral gliomas. This study explores the regional uptake and cellular targets of 68Ga-PSMA and 18F-DCFPyL in three different rat glioma models. METHODS:F98, 9 L, or U87 rat gliomas were implanted into the brains of 38 rats. After 13 days of tumor growth, 68Ga-PSMA (n = 21) or 18F-DCFPyL (n = 17) was injected intravenously, and animals were sacrificed 40 min later. Five animals for each tracer and tumor model were additionally investigated by micro-PET at 20-40 min post injection. Cryosections of the tumor bearing brains were analyzed by ex vivo autoradiography and immunofluorescence staining for blood vessels, microglia, astrocytes, and presence of PSMA. Blood-brain barrier (BBB) permeability was tested by coinjection of Evans blue dye (EBD). 68Ga-PSMA uptake after restoration of BBB integrity by treatment with dexamethasone (Dex) was evaluated in four animals with U87 gliomas. Competition experiments using the PSMA-receptor inhibitor 2-(phosphonomethyl)pentane-1,5-dioic acid (PMPA) were performed for both tracers in two animals each. RESULTS:Autoradiography demonstrated a strong 68Ga-PSMA and 18F-DCFPyL binding in the peritumoral area and moderate binding in the center of the tumors. PMPA administration led to complete inhibition of 68Ga-PSMA and 18F-DCFPyL binding in the peritumoral region. Restoration of BBB by Dex treatment reduced EBD extravasation but 68Ga-PSMA binding remained unchanged. Expression of activated microglia (CD11b) was low in the intra- and peritumoral area but GFAP staining revealed strong activation of astrocytes in congruency to the tracer binding in the peritumoral area. All tumors were visualized in micro PET, showing a lower tumor/brain contrast with 68Ga-PSMA than with 18F-DCFPyL. CONCLUSIONS:High uptake of 68Ga-PSMA and 18F-DCFPyL in the peritumoral area of all glioma models is presumably caused by activated astrocytes. This may represent a limitation for the clinical application of PSMA ligands in gliomas.

Project description:Despite the progress in diagnosis and treatment, prostate cancer (PCa) is one of the main causes for cancer-associated deaths among men. Recently, prostate-specific membrane antigen (PSMA) binding tracers have revolutionized the molecular imaging of this disease. The translation of these tracers into therapeutic applications is challenging because of high PSMA-associated kidney uptake. While both the tumor uptake and the uptake in the kidneys are PSMA-specific, the kidneys show a more rapid clearance than tumor lesions. Consequently, the potential of endoradiotherapeutic drugs targeting PSMA is highly dependent on a sustained retention in the tumor - ideally achieved by predominant internalization of the respective tracer. Previously, we were able to show that the pharmacokinetics of the tracers containing the Glu-urea-based binding motif can be further enhanced with a specifically designed linker. Here, we evaluate an eventual influence of the chelator moiety on the pharmacokinetics, including the tumor internalization. A series of tracers modified by different chelators were synthesized using solid phase chemistry. The conjugates were radiolabeled to evaluate the influence on the receptor binding affinity, the ligand-induced internalization and the biodistribution behavior. Competitive binding and internalization assays were performed on PSMA positive LNCaP cells and the biodistribution of the most promising compound was evaluated by positron emission tomography (PET) in LNCaP-tumor-bearing mice. Interestingly, conjugation of the different chelators did not cause significant differences: all compounds showed nanomolar binding affinities with only minor differences. PET imaging of the (68)Ga-labeled CHX-A''-DTPA conjugate revealed that the chelator moiety does not impair the specificity of tumor uptake when compared to the gold standard PSMA-617. However, strong differences of the internalization ratios caused by the chelator moiety were observed: differences in internalization between 15% and 65% were observed, with the CHX-A''-DTPA conjugate displaying the highest internalization ratio. A first-in-man PET/CT study proved the high tumor uptake of this (68)Ga-labeled PSMA-targeting compound. These data indicate that hydrophobic entities at the chelator mediate the internalization efficacy. Based on its specific tumor uptake in combination with its very high internalization ratio, the clinical performance of the chelator-conjugated Glu-urea-based PSMA inhibitors will be further elucidated.

Dataset Information

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.

Publications

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.

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