Dataset Information

Preclinical Evaluation of [¹⁸F]FACH in Healthy Mice and Piglets: An ¹⁸F-Labeled Ligand for Imaging of Monocarboxylate Transporters with PET.

ABSTRACT: The expression of monocarboxylate transporters (MCTs) is linked to pathophysiological changes in diseases, including cancer, such that MCTs could potentially serve as diagnostic markers or therapeutic targets. We recently developed [¹⁸F]FACH as a radiotracer for non-invasive molecular imaging of MCTs by positron emission tomography (PET). The aim of this study was to evaluate further the specificity, metabolic stability, and pharmacokinetics of [¹⁸F]FACH in healthy mice and piglets. We measured the [¹⁸F]FACH plasma protein binding fractions in mice and piglets and the specific binding in cryosections of murine kidney and lung. The biodistribution of [¹⁸F]FACH was evaluated by tissue sampling ex vivo and by dynamic PET/MRI in vivo, with and without pre-treatment by the MCT inhibitor ?-CCA-Na or the reference compound, FACH-Na. Additionally, we performed compartmental modelling of the PET signal in kidney cortex and liver. Saturation binding studies in kidney cortex cryosections indicated a K_D of 118 ± 12 nM and B_max of 6.0 pmol/mg wet weight. The specificity of [¹⁸F]FACH uptake in the kidney cortex was confirmed in vivo by reductions in AUC_0-60min after pre-treatment with ?-CCA-Na in mice (-47%) and in piglets (-66%). [¹⁸F]FACH was metabolically stable in mouse, but polar radio-metabolites were present in plasma and tissues of piglets. The [¹⁸F]FACH binding potential (BP_ND) in the kidney cortex was approximately 1.3 in mice. The MCT1 specificity of [¹⁸F]FACH uptake was confirmed by displacement studies in 4T1 cells. [¹⁸F]FACH has suitable properties for the detection of the MCTs in kidney, and thus has potential as a molecular imaging tool for MCT-related pathologies, which should next be assessed in relevant disease models.

SUBMITTER: Gundel D

PROVIDER: S-EPMC7915902 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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Preclinical Evaluation of [18F]FACH in Healthy Mice and Piglets: An 18F-Labeled Ligand for Imaging of Monocarboxylate Transporters with PET.

Gündel Daniel D Sadeghzadeh Masoud M Deuther-Conrad Winnie W Wenzel Barbara B Cumming Paul P Toussaint Magali M Ludwig Friedrich-Alexander FA Moldovan Rareş-Petru RP Kranz Mathias M Teodoro Rodrigo R Sattler Bernhard B Sabri Osama O Brust Peter P

International journal of molecular sciences 20210206 4

The expression of monocarboxylate transporters (MCTs) is linked to pathophysiological changes in diseases, including cancer, such that MCTs could potentially serve as diagnostic markers or therapeutic targets. We recently developed [18F]FACH as a radiotracer for non-invasive molecular imaging of MCTs by positron emission tomography (PET). The aim of this study was to evaluate further the specificity, metabolic stability, and pharmacokinetics of [18F]FACH in healthy mice and ...[more]

PMID: 33562048

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Project description:Overexpression of monocarboxylate transporters (MCTs) has been shown for a variety of human cancers (e.g., colon, brain, breast, and kidney) and inhibition resulted in intracellular lactate accumulation, acidosis, and cell death. Thus, MCTs are promising targets to investigate tumor cancer metabolism with positron emission tomography (PET). Here, the organ doses (ODs) and the effective dose (ED) of the first 18F-labeled MCT1/MCT4 inhibitor were estimated in juvenile pigs. Whole-body dosimetry was performed in three piglets (age: ~6 weeks, weight: ~13-15 kg). The animals were anesthetized and subjected to sequential hybrid Positron Emission Tomography and Computed Tomography (PET/CT) up to 5 h after an intravenous (iv) injection of 156 ± 54 MBq [18F]FACH. All relevant organs were defined by volumes of interest. Exponential curves were fitted to the time-activity data. Time and mass scales were adapted to the human order of magnitude and the ODs calculated using the ICRP 89 adult male phantom with OLINDA 2.1. The ED was calculated using tissue weighting factors as published in Publication 103 of the International Commission of Radiation Protection (ICRP103). The highest organ dose was received by the urinary bladder (62.6 ± 28.9 µSv/MBq), followed by the gall bladder (50.4 ± 37.5 µSv/MBq) and the pancreas (30.5 ± 27.3 µSv/MBq). The highest contribution to the ED was by the urinary bladder (2.5 ± 1.1 µSv/MBq), followed by the red marrow (1.7 ± 0.3 µSv/MBq) and the stomach (1.3 ± 0.4 µSv/MBq). According to this preclinical analysis, the ED to humans is 12.4 µSv/MBq when applying the ICRP103 tissue weighting factors. Taking into account that preclinical dosimetry underestimates the dose to humans by up to 40%, the conversion factor applied for estimation of the ED to humans would rise to 20.6 µSv/MBq. In this case, the ED to humans upon an iv application of ~300 MBq [18F]FACH would be about 6.2 mSv. This risk assessment encourages the translation of [18F]FACH into clinical study phases and the further investigation of its potential as a clinical tool for cancer imaging with PET.

Project description:The human growth factor receptor type 2 (HER2) is overexpressed in breast as well as other types of cancer. Immuno-PET, a noninvasive imaging procedure that could assess HER2 status in both primary and metastatic lesions simultaneously, could be a valuable tool for optimizing application of HER2-targeted therapies in individual patients. Herein, we have evaluated the tumor-targeting potential of the 5F7 anti-HER2 Nanobody (single-domain antibody fragment; ?13 kDa) after (18)F labeling by 2 methods.The 5F7 Nanobody was labeled with (18)F using the novel residualizing label N-succinimidyl 3-((4-(4-(18)F-fluorobutyl)-1H-1,2,3-triazol-1-yl)methyl)-5-(guanidinomethyl)benzoate ((18)F-SFBTMGMB; (18)F-RL-I) and also via the most commonly used (18)F protein-labeling prosthetic agent N-succinimidyl 3-(18)F-fluorobenzoate ((18)F-SFB). For comparison, 5F7 Nanobody was also labeled using the residualizing radioiodination agent N-succinimidyl 4-guanidinomethyl-3-(125)I-iodobenzoate ((125)I-SGMIB). Paired-label ((18)F/(125)I) internalization assays and biodistribution studies were performed on HER2-expressing BT474M1 breast carcinoma cells and in mice with BT474M1 subcutaneous xenografts, respectively. Small-animal PET/CT imaging of 5F7 Nanobody labeled using (18)F-RL-I also was performed.Internalization assays indicated that intracellularly retained radioactivity for (18)F-RL-I-5F7 was similar to that for coincubated (125)I-SGMIB-5F7, whereas that for (18)F-SFB-5F7 was lower than coincubated (125)I-SGMIB-5F7 and decreased with time. BT474M1 tumor uptake of (18)F-RL-I-5F7 was 28.97 ± 3.88 percentage injected dose per gram of tissue (%ID/g) at 1 h and 36.28 ± 14.10 %ID/g at 2 h, reduced by more than 90% on blocking with trastuzumab, indicating HER2 specificity of uptake, and was also 26%-28% higher (P < 0.05) than that of (18)F-SFB-5F7. At 2 h, the tumor-to-blood ratio for (18)F-RL-I-5F7 (47.4 ± 13.1) was significantly higher (P < 0.05) than for (18)F-SFB-5F7 (25.4 ± 10.3); however, kidney uptake was 28-36-fold higher for (18)F-RL-I-5F7.(18)F-RL-I-5F7 is a promising tracer for evaluating HER2 status by immuno-PET; however, in settings in which renal background is problematic, strategies for reducing its kidney uptake may be needed.

Project description:OBJECTIVE:Epidermal growth factor receptor (EGFR) is a theranostic biomarker for a variety of cancer types. The aim of the present study was to develop an 18F radiolabeled EGFR targeting RNA aptamer, and to investigate its ability to visualize and quantify EGFR in xenograft models. METHODS:Biolayer interferometry binding assay was used to detect the binding affinity of the alkyne-modified EGFR aptamer MinE07 (denoted as ME07) with recombinant human wild-type EGFR protein and the mutant EGFRvIII protein. Cy5-conjugated ME07 was used for flow cytometry and immunofluorescence staining, and an Alexa Fluor 488-labeled EGFR antibody (ab193244) was used as a control. 18F-Fluorobenzoyl (FB) azide was employed as a synthon to produce 18F-FB-ME07 via click chemistry, and the cellular uptake and internalization characteristics of 18F-FB-ME07 were investigated. Static PET scans, 60-min dynamic scans, and biodistribution study of 18F-FB-ME07 were performed in three types of tumor models. RESULTS:The Kd values of ME07 to wtEGFR and EGFRvIII proteins were 0.3 nM and 271 nM respectively. The A431, U87MG, and HCT-116 cells showed strong, weak, and negative binding with Cy5-ME07, which is consistent with EGFR expression level in these cells. Peak cell uptake values of 18F-FB-ME07 in A431, U87MG and HCT-116 cells were 2.86%, 2.19% and 0.88% of the added dose respectively. The mean internalization of 18F-FB-ME07 in these cells were 60.02%, 53.1%, and 52.8% of the total accumulated radioactivity. In static PET imaging, despite high uptake in the liver and kidneys, 18F-FB-ME07 showed reasonable accumulation in A431 tumors (1.02?±?0.13 %ID/g at 30 min after injection). Of note, the uptake of 18F-FB-ME07 in A431 xenografts was significantly higher than that in U87MG and HCT-116 xenografts. In A431 xenografted mice, the tumor/blood ratio was 3.89 and the tumor/muscle ratio reached 8.65. CONCLUSIONS:We for the first time generated an aptamer-derived EGFR targeting PET tracer 18F-FB-ME07, which showed highly selective targeting ability in mouse tumor models expressing different levels of EGFR. Our results suggest that 18F-FB-ME07 is a potential EGFR targeting molecular imaging probe for future clinical translation.

Project description:Radiofluorinated benzamide and nicotinamide analogues are promising molecular probes for the positron emission tomography (PET) imaging of melanoma. Compounds containing aromatic (benzene or pyridine) and N,N-diethylethylenediamine groups have been successfully used for development of melanin targeted PET and single-photon emission computed tomography (SPECT) imaging agents for melanoma. The objective of this study was to determine the feasibility of using aliphatic compounds as a molecular platform for the development of a new generation of PET probes for melanoma detection. An aliphatic N,N-diethylethylenediamine precursor was directly coupled to a radiofluorination synthon, p-nitrophenyl 2-(18)F-fluoropropionate ((18)F-NFP), to produce the probe N-(2-(diethylamino)ethyl)-2-(18)F-fluoropropanamide ((18)F-FPDA). The melanoma-targeting ability of (18)F-FPDA was further evaluated both in vitro and in vivo through cell uptake assays, biodistribution studies, and small animal PET imaging in C57BL/6 mice bearing B16F10 murine melanoma tumors. Beginning with the precursor (18)F-NFP, the total preparation time for (18)F-FPDA, including the final high-performance liquid chromatography purification step, was approximately 30 min, with a decay-corrected radiochemical yield of 79.8%. The melanin-targeting specificity of (18)F-FPDA was demonstrated by significantly different uptake rates in tyrosine-treated and untreated B16F10 cells in vitro. The tumor uptake of (18)F-FPDA in vivo reached 2.65 ± 0.48 %ID/g at 2 h postinjection (p.i.) in pigment-enriched B16F10 xenografts, whereas the tumor uptake of (18)F-FPDA was close to the background levels, with rates of only 0.37 ± 0.07 %ID/g at 2 h p.i. in the nonpigmented U87MG tumor mouse model. Furthermore, small animal PET imaging studies revealed that (18)F-FPDA specifically targeted the melanotic B16F10 tumor, yielding a tumor-to-muscle ratio of approximately 4:1 at 1 h p.i. and 7:1 at 2 h p.i. In summary, we report the development of a novel (18)F-labeled aliphatic compound for melanoma imaging that can be easily synthesized in high yields using the radiosynthon (18)F-NFP. The PET probe (18)F-FPDA exhibits high B16F10 tumor-targeting efficacy and favorable in vivo pharmacokinetics. Our study demonstrates that aliphatic compounds can be used as a new generation molecular platform for the development of novel melanoma targeting agents. Further evaluation and optimization of (18)F-FPDA for melanin targeted molecular imaging are therefore warranted.

Project description:Integrin ?v?6 is a cell surface receptor minimally expressed by healthy tissue but elevated in lung, colon, skin, ovarian, cervical, and pancreatic cancers. A molecular PET agent for integrin ?v?6 could provide significant clinical utility by facilitating both cancer staging and treatment monitoring to more rapidly identify an effective therapeutic approach.Here, we evaluated 2 cystine knot peptides, R01 and S02, previously engineered with a 3-6 nM affinity for integrin ?v?6, for (18)F radiolabeling and PET imaging of BxPC3 pancreatic adenocarcinoma xenografts in mice. Cystine knot peptides were labeled with N-succinimidyl-4-(18)F-fluorobenzoate and evaluated for binding affinity and serum stability. Peptides conjugated with (18)F-fluorobenzoate (2-3 MBq) were injected via the tail vein into nude mice xenografted with BxPC3 (integrin ?v?6-positive) or 293 (integrin ?v?6-negative) tumors. Small-animal PET scans were acquired at 0.5, 1, and 2 h after injection. Ex vivo ?-counting of dissected tissues was performed at 0.5 and 2 h.(18)F-fluorobenzoate peptides were produced in 93% ((18)F-fluorobenzoate-R01) and 99% ((18)F-fluorobenzoate-S02) purity. (18)F-fluorobenzoate-R01 and (18)F-fluorobenzoate-S02 had affinities of 1.1 ± 0.2 and 0.7 ± 0.4 nM, respectively, and were 87% and 94%, respectively, stable in human serum at 37°C for 2 h. (18)F-fluorobenzoate-R01 and (18)F-fluorobenzoate-S02 exhibited 2.3 ± 0.6 and 1.3 ± 0.4 percentage injected dose per gram (%ID/g), respectively, in BxPC3 xenografted tumors at 0.5 h (n = 4-5). Target specificity was confirmed by low tumor uptake in integrin ?v?6-negative 293 tumors (1.4 ± 0.6 and 0.5 ± 0.2 %ID/g, respectively, for (18)F-fluorobenzoate-R01 and (18)F-fluorobenzoate-S02; both P < 0.05; n = 3-4) and low muscle uptake (3.1 ± 1.0 and 2.7 ± 0.4 tumor to muscle for (18)F-fluorobenzoate-R01 and (18)F-fluorobenzoate-S02, respectively). Small-animal PET data were corroborated by ex vivo ?-counting of dissected tissues, which demonstrated low uptake in nontarget tissues with only modest kidney uptake (9.2 ± 3.3 and 1.9 ± 1.2 %ID/g, respectively, at 2 h for (18)F-fluorobenzoate-R01 and (18)F-fluorobenzoate-S02; n = 8). Uptake in healthy pancreas was low (0.3% ± 0.1% for (18)F-fluorobenzoate-R01 and 0.03% ± 0.01% for (18)F-fluorobenzoate-S02; n = 8).These cystine knot peptide tracers, in particular (18)F-fluorobenzoate-R01, show translational promise for molecular imaging of integrin ?v?6 overexpression in pancreatic and other cancers.

Dataset Information

Preclinical Evaluation of [¹⁸F]FACH in Healthy Mice and Piglets: An ¹⁸F-Labeled Ligand for Imaging of Monocarboxylate Transporters with PET.

Publications

Preclinical Evaluation of [<sup>18</sup>F]FACH in Healthy Mice and Piglets: An <sup>18</sup>F-Labeled Ligand for Imaging of Monocarboxylate Transporters with PET.

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