GMP in Radiopharmacy:the current situation in its context

Over the last decades, Good Manufacturing Practice (GMP) has evolved from a kind of uncomfortable requirement to an indispensable tool for the production and quality control of state of the art pharmaceuticals. Somewhat later than regular pharmacy, also radiopharmacy was encouraged to comply with GMP. The short version of this story, is that this was not a straightforward process. For example, in the year 2000, it was still a common opinion that GMP for the radiopharmacy could consist of a kind of “light version” compared to the GMP regulations used within the pharmaceutical industry. As the involvement of Inspectorates and Industries in Radiopharmacy increased, GMP was there to stay. And, as we will see in this chapter, not in a kind of “light version.” The aim of this chapter is to give a concise overview on radiopharmaceutical GMP. Furthermore, some future perspectives are provided to point out where it may lead us

Carotid Plaque Imaging with SPECT/CT and PET/CT

A major contributor to the occurrence of ischemic stroke is the existence of carotid atherosclerosis. A vulnerable carotid atherosclerotic plaque may rupture or erode, thus causing a thrombotic event. Currently, clinical decision-making with regard to carotid endarterectomy or stenting is still primarily based on the extent of luminal stenosis, estimated with CT angiography and/or (duplex) ultrasonography. However, there is growing evidence that the anatomic impact of stenosis alone has limited value in predicting the exact consequences of plaque vulnerability. Various molecular processes have, independently of degree of stenosis, shown to be importantly associated with the plaque's capability to cause thrombotic events. These molecular processes can be visualized with nuclear medicine techniques allowing the identification of vulnerable patients by non-invasive in vivo SPECT(/CT) and PET(/CT) imaging. This chapter provides an overview of SPECT(/CT) and PET(/CT) imaging with specific radiotracers that have been evaluated for the detection of plaques together with a future perspective in this field of imaging.</p

Photoresponsive molecular tools for emerging applications of light in medicine

Light-based therapeutic and imaging modalities, which emerge in clinical applications, rely on molecular tools, such as photocleavable protecting groups and photoswitches that respond to photonic stimulus and translate it into a biological effect. However, optimisation of their key parameters (activation wavelength, band separation, fatigue resistance and half-life) is necessary to enable application in the medical field. In this perspective, we describe the applications scenarios that can be envisioned in clinical practice and then we use those scenarios to explain the necessary properties that the photoresponsive tools used to control biological function should possess, highlighted by examples from medical imaging, drug delivery and photopharmacology. We then present how the (photo)chemical parameters are currently being optimized and an outlook is given on pharmacological aspects (toxicity, solubility, and stability) of light-responsive molecules. With these interdisciplinary insights, we aim to inspire the future directions for the development of photocontrolled tools that will empower clinical applications of light

The Development of a Smart Magnetic Resonance Imaging and Chemical Exchange Saturation Transfer Contrast Agent for the Imaging of Sulfatase Activity

The molecular imaging of biomarkers plays an increasing role in medical diagnostics. In particular, the imaging of enzyme activity is a promising approach, as it enables the use of its inherent catalytic activity for the amplification of an imaging signal. The increased activity of a sulfatase enzyme has been observed in several types of cancers. We describe the development and in vitro evaluation of molecular imaging agents that allow for the detection of sulfatase activity using the whole-body, non-invasive MRI and CEST imaging methods. This approach relies on a responsive ligand that features a sulfate ester moiety, which upon sulfatase-catalyzed hydrolysis undergoes an elimination process that changes the functional group, coordinating with the metal ion. When Gd3+ is used as the metal, the complex can be used for MRI, showing a 25% decrease at 0.23T and a 42% decrease at 4.7T in magnetic relaxivity after enzymatic conversion, thus providing a "switch-off" contrast agent. Conversely, the use of Yb3+ as the metal leads to a "switch-on" effect in the CEST imaging of sulfatase activity. Altogether, the results presented here provide a molecular basis and a proof-of-principle for the magnetic imaging of the activity of a key cancer biomarker. </p

Test-Retest Stability of Cerebral 2-Deoxy-2-[F-18]Fluoro-D-Glucose ([F-18]FDG) Positron Emission Tomography (PET) in Male and Female Rats

Purpose: An important issue in rodent imaging is the question whether a mixed population of male and female animals can be used rather than animals of a single sex. For this reason, the present study examined the test-retest stability of positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG inmale rats and female rats at different phases of the estrous cycle. Procedures: Long Evans rats (age 1 year) were divided into three groups: (1) males (n = 6), (2) females in metestrous (low estrogen levels, n = 9), and (3) females in proestrous (high estrogen levels, n = 7). Two standard [18F]FDG scans with rapid arterial blood sampling were made at an interval of 10 days in subjects anesthetized with isoflurane and oxygen. Body temperature, heart rate, and blood oxygenation were continuously monitored. Regional cerebral metabolic rates of glucose were calculated using a Patlak plot with plasma radioactivity as input function. Results: Regional metabolic rate of glucose (rCMRglucose) in male and female rats, or [18F]FDG uptake in females at proestrous and metestrous, was not significantly different, but females showed significantly higher standardized uptake values (SUVs) and Patlak flux than males, particularly in the initial scan. The relative difference between the scans and the test-retest variability (TRV) were greater in females than in males. Intra-class correlation coefficients (ICCs) of rCMRglucose, SUV, normalized SUV, and glucose flux were good to excellent in males but poor to moderate in females. Conclusions: Based on these data for [18F]FDG, the mixing of sexes in imaging studies of the rodent brain will result in an impaired test-retest stability of PET data and a need for larger group sizes to maintain statistical power in group comparisons. The observed differences between males and females do not indicate any specific gender difference in cerebral metabolism but are related to different levels of non-radioactive glucose in blood plasma during isoflurane anesthesia

Serial [F-18]-FDHT-PET to predict bicalutamide efficacy in patients with androgen receptor positive metastatic breast cancer

Background: The androgen receptor (AR) is a potential target in metastatic breast cancer (MBC), and 16 beta-[F-18]-fluoro-5 alpha-dihydrotestosterone positron emission tomography ([F-18]-FDHT-PET) can be used for noninvasive visualisation of AR. [F-18]-FDHT uptake reduction during AR-targeting therapy reflects AR occupancy and might be predictive for treatment response. We assessed the feasibility of [F-18]-FDHT-PET to detect changes in AR availability during bicalutamide treatment and correlated these changes with treatment response. Patients and methods: Patients with AR thorn MBC, regardless of oestrogen receptor status, received an [F-18]-FDHT-PET at baseline and after 4-6 weeks bicalutamide treatment. Baseline [F-18]-FDHT uptake was expressed as maximum standardised uptake value. Percentage change in tracer uptake, corrected for background activity (SUVcor), between baseline and follow-up PET scan (% reduction), was assessed per-patient and lesion. Clinical benefit was determined in accordance with Response Evaluation Criteria in Solid Tumours (RECIST) 1.1 or clinical evaluation (absence of disease progression for >= 24 weeks). Results: Baseline [F-18]-FDHT-PET in 21 patients detected 341 of 515 lesions found with standard imaging and 21 new lesions. Follow-up [F-18]-FDHT- PET was evaluable in 17 patients with 349 lesions, showing a decrease in median SUVcor from 1.3 to 0.7 per-patient and lesion (P <0.001). Median % reduction per-patient was - 45% and per-lesion -39%. In patients with progressive disease (n Z 11), median % reduction was -30% versus -53% for patients who showed clinical benefit (in accordance with RECIST (n = 3) or clinical evaluation (n = 3); P Z 0.338). Conclusion: In this feasibility study, a bicalutamide-induced reduction in [F-18]-FDHT uptake could be detected by follow-up [F-18]-FDHT-PET in patients with AR thorn MBC. However, this change could not predict bicalutamide response. (C) 2020 The Authors. Published by Elsevier Ltd

Feasibility of ex vivo fluorescence imaging of angiogenesis in (non-) culprit human carotid atherosclerotic plaques using bevacizumab-800CW

Vascular endothelial growth factor-A (VEGF-A) is assumed to play a crucial role in the development and rupture of vulnerable plaques in the atherosclerotic process. We used a VEGF-A targeted fluorescent antibody (bevacizumab-IRDye800CW [bevacizumab-800CW]) to image and visualize the distribution of VEGF-A in (non-)culprit carotid plaques ex vivo. Freshly endarterectomized human plaques (n = 15) were incubated in bevacizumab-800CW ex vivo. Subsequent NIRF imaging showed a more intense fluorescent signal in the culprit plaques (n = 11) than in the non-culprit plaques (n = 3). A plaque received from an asymptomatic patient showed pathologic features similar to the culprit plaques. Cross-correlation with VEGF-A immunohistochemistry showed co-localization of VEGF-A over-expression in 91% of the fluorescent culprit plaques, while no VEGF-A expression was found in the non-culprit plaques (p < 0.0001). VEGF-A expression was co-localized with CD34, a marker for angiogenesis (p < 0.001). Ex vivo near-infrared fluorescence (NIRF) imaging by incubation with bevacizumab-800CW shows promise for visualizing VEGF-A overexpression in culprit atherosclerotic plaques in vivo

Improved GMP-compliant multi-dose production and quality control of 6-[18F]fluoro-L-DOPA

Background: 6-[18F]Fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) is a frequently used radiopharmaceutical for detecting neuroendocrine and brain tumors and for the differential diagnosis of Parkinson’s disease. To meet the demand for FDOPA, a high-yield GMP-compliant production method is required. Therefore, this study aimed to improve the FDOPA production and quality control procedures to enable distribution of the radiopharmaceutical over distances. FDOPA was prepared by electrophilic fluorination of the trimethylstannyl precursor with [18F]F2, produced from [18O]2 via the double-shoot approach, leading to FDOPA with higher specific activity as compared to FDOPA which was synthesized, using [18F]F2 produced from 20Ne, leading to FDOPA with a lower specific activity. The quality control of the product was performed using a validated UPLC system and compared with quality control with a conventional HPLC system. Impurities were identified using UPLC-MS. Results: The [18O]2 double-shoot radionuclide production method yielded significantly more [18F]F2 with less carrier F2 than the conventional method starting from 20Ne. After adjustment of radiolabeling parameters substantially higher amounts of FDOPA with higher specific activity could be obtained. Quality control by UPLC was much faster and detected more side-products than HPLC. UPLC-MS showed that the most important side-product was FDOPA-quinone, rather than 6-hydroxydopa as suggested by the European Pharmacopoeia. Conclusion: The production and quality control of FDOPA were significantly improved by introducing the [18O]2 double-shoot radionuclide production method, and product analysis by UPLC, respectively. As a result, FDOPA is now routinely available for clinical practice and for distribution over distances

Distribution of Matrix Metalloproteinases in Human Atherosclerotic Carotid Plaques and Their Production by Smooth Muscle Cells and Macrophage Subsets

In this study, the potential of matrix metalloproteinase (MMP) sense for detection of atherosclerotic plaque instability was explored. Secondly, expression of MMPs by macrophage subtypes and smooth muscle cells (SMCs) was investigated. Twenty-three consecutive plaques removed during carotid endarterectomy were incubated in MMPSense (TM) 680 and imaged with IVISA (R) Spectrum. mRNA levels of MMPs, macrophage markers, and SMCs were determined in plaque specimens, and in in vitro differentiated M1 and M2 macrophages. There was a significant difference between autofluorescence signals and MMPSense signals, both on the intraluminal and extraluminal sides of plaques. MMP-9 and CD68 messenger RNA (mRNA) expression was higher in hot spots, whereas MMP-2 and alpha SMA expression was higher in cold spots. In vitro M2 macrophages had higher mRNA expression of MMP-1, MMP-9, MMP-12, and TIMP-1 compared to M1 macrophages. MMP-9 is most dominantly MMP present in atherosclerotic plaques and is produced by M2 rather than M1 macrophages

Characterization of a novel model for atherosclerosis imaging:the apolipoprotein E-deficient rat

Background: The apolipoprotein E-deficient (apoE −/−) mouse is a well-established model for studying atherosclerosis. However, its small size limits its use in longitudinal positron emission tomography (PET) imaging studies. Recently, the apoE −/− rat has emerged as an alternative. With this study, we investigate the feasibility of using apoE −/− rats as an in vivo model for longitudinal atherosclerotic PET/CT imaging.Results: ApoE −/− rats showed significantly higher [18F]FDG uptake than controls in the aortic arch (+ 18.5%, p &lt; 0.001) and abdominal aorta (+ 31.0%, p &lt; 0.001) at weeks 12, 26, and 51. ApoE −/− rats exhibited hypercholesterolemia, as evidenced by plasma cholesterol levels that were up to tenfold higher, and total hepatic cholesterol levels that were up to threefold higher than the control rats at the end of the study. Fast protein liquid chromatography cholesterol profiling indicated very high levels of pro-atherogenic apoB-containing very low-density lipoprotein and low-density lipoprotein fractions in the apoE −/− rats. Atherosclerotic lesions cover 19.9% of the surface of the aortic arch (p = 0.0013), and there was a significantly higher subendothelial accumulation of ED1-positive macrophages in the abdominal aorta of the apoE −/− rats compared to control rats (Ctrl) (p = 0.01). No differences in neutral sterols were observed but higher levels of bile acids were found in the apoE −/− rats. Conclusion: These data demonstrate early signs of hypercholesterolemia, high levels of bile acids, the development of atherosclerotic lesions, and macrophage accumulation in apoE −/− rats. Therefore, this model shows promise for atherosclerosis imaging studies.</p