Gallium-68 radiolabeling of biomolecules for positron emission tomography with special reference to imaging of inflammation and bone

Positron emission tomography (PET) radiopharmaceuticals are composed of a positron emitting radionuclide (e.g. gallium-68) and a molecular structure. MicroRNA-21 is a relevant target overexpressed in many diseases, such as osteoporosis and osteosarcoma. Interference of microRNA-21 by anti-microRNA-21 would be a potential medicinal treatment. 3′-NOTA-chelated anti-microRNA-21 was radiolabeled with gallium-68 using the fractionated method and mixed with 5′-alendronate-conjugated microRNA-21. 68Ga-labeled double helix was formed rapidly at room temperature. The double helix thus formed was in vivo PET imaged to evaluate whether its bone accumulation was increased because of conjugated bis(phosphonate). PET imaging revealed that bis(phosphonate)-conjugated anti-microRNA-21 accumulates in the bone. This observation can be utilized in the future when developing medicinal treatments for diseases involving micro-RNA-21. Sialic acid-binding immunoglobulin-like lectin-9 (Siglec-9) is a leukocyte ligand of vascular adhesion protein-1 (VAP-1). VAP-1 plays an important role in many inflammatory conditions. Inflammation has s signicifant part in a number of diseases, such as atherosclerosis and diabetes. PET imaging provides tools for studying the mechanisms related to the process of inflammation and to discover potential targeted therapeutics. [68Ga]Ga-DOTA-Siglec-9 can be used as a PET tracer for imaging of inflammation. The purpose of this thesis was to develop an automated protocol for producing GMP-grade inflammation imaging agent [68Ga]Ga-DOTA-Siglec-9 for first-inhuman studies. This GMP-grade tracer was produced using a fully automated acetone-based method. It was concluded that this method facilitates efficient production of GMP-grade [68Ga]Ga-DOTA-Siglec-9 and the tracer is suitable for human use

Lääkeaineiden vesiliukoisuuden parantaminen

Monien potentiaalisten lääkeainekandidaattien vesiliukoisuus on huono. Tämä on merkittävä ongelma pyrittäessä kehittämään niistä valmiita lääkkeitä. Lääkeainekandidaattien vesiliukoisuus riippuu niiden kemiallisesta rakenteesta. Tutkielmassa esitetään erilaisia menetelmiä kiinteiden lääkeaineiden vesiliukoisuuden parantamiseksi. Kemiallisia menetelmiä ovat suolanmuodostus, pH:n muuttaminen ja aihiolääkkeen (engl. prodrug) valmistaminen. Aihiolääke on farmakologisesti inaktiivinen yhdiste, joka metaboloituu elimistössä aktiiviseksi lääkeaineeksi. Aihiolääkettä valmistettaessa muokataan lääkeaineen kemiallista rakennetta liittämällä siihen vesiliukoisuutta lisäävä rakenne. Vesiliukoisuutta lisäävänä rakenteena voi toimia fosfaatti tai sokeri, ionisoituva orgaaninen happo tai emäs tai neutraali ryhmä. Yksi yleisimmistä menetelmistä aihiolääkkeen valmistamiseksi on käyttää aihio-osana fosforihapon estereitä tai amideja. Fysikaalisia ja muita menetelmiä ovat esimerkiksi kiinteiden dispersioiden,nanopartikkeleiden tai nanosuspensioiden valmistaminen, kiderakenteen muokkaaminen ja syklodekstriinien hyödyntäminen inkluusiokompleksien muodostamiseksi. Tutkielman kokeellisessa osassa tutkittiin lääkeainekandidaatti DPMBA:n (N-(4,6- dimetyylipyrimidin-2-yyli)-4-[(2-metyylibentsyyli)amino]bentseenisulfonamidi) fosfaattimonoesterin valmistusta. DPMBA on selektiivinen alpha2-antagonisti eli adrenoseptorien salpaaja. Kyseistä lääkeainekandidaattia voisi mahdollisesti hyödyntää sydän- ja verenkiertoelimistön sairauksien hoidossa. DPMBA:n ongelmana on sen huono vesiliukoisuus fysiologisessa pH:ssa, joten sen farmakologiset ominaisuudet ovat huonot. Kokeellisen osan tavoitteena oli parantaa DPMBA:n vesiliukoisuutta valmistamalla siitä aihiolääke. Aihiolääkkeen valmistus sisälsi DPMBA:n synteesin kehitystä ja aihiolääkkeen valmistuksessa tarvittavien kloorimetyylifosfaattien synteesit. Aihio-osien liittämistä DPMBA:han kokeiltiin erilaisin menetelmin. Lisäksi tutkittiin kloorimetyylifosfaattien liittämistä DPMBA:n lähtöaineisiin sekä muihin samankaltaisiin primaarisiin ja sekundaarisiin amiineihin. DPMBA:n kemiallinen rakenne on haastava, eikä kokeiltuja fosfaattiaihio-osia saatu liitettyä siihen. DPMBA:n rakenteessa oleva sulfonyyliryhmä, elektroneja puoleensavetävänä ryhmänä, heikentää rakenteessa olevien sekundaaristen typpiatomien nukleofiilisyyttä. Aihiolääkkeen valmistamisen sijaan kyseeseen voisi tulla jokin fysikaalinen menetelmä DPMBA:n vesiliukoisuuden parantamiseksi.Siirretty Doriast

Targeting of vascular adhesion protein-1 by positron emission tomography visualizes sites of inflammation in Borrelia burgdorferi-infected mice

Background: In the present study, we sought to evaluate the feasibility of targeting vascular adhesion protein-1 (VAP-1) by positron emission tomography (PET) for the longitudinal quantitative assessment of Borrelia burgdorferi infection-induced inflammation in mice.Methods: Mice with B. burgdorferi infection-induced arthritis were studied. During a 7-week follow-up period, the progression of arthritis was monitored weekly with 68Ga-DOTA-Siglec-9 PET/computed tomography (CT) and measurement of tibiotarsal joint swellings. A subgroup of infected mice was treated with ceftriaxone. Finally, histopathological assessment of joint inflammation was performed and VAP-1 expression in joints were determined.Results: Explicit joint swelling and 68Ga-DOTA-Siglec-9 uptake could be demonstrated in the affected joints from B. burgdorferi-infected mice. By contrast, no obvious accumulation of 68Ga-DOTA-Siglec-9 was detected in joints of uninfected mice. The maximum swelling and highest uptake in the affected joints were observed 4 weeks after the infection. 68Ga-DOTA-Siglec-9 uptake in joints correlated with joint swelling (P < 0.0001) and histopathological scoring of inflammation (P = 0.020). Despite short-term antibiotic treatment, the arthritis persisted, and the PET signal remained as high as in nontreated mice. Immunohistochemistry revealed strong-to-moderate expression of VAP-1 in the synovium of B. burgdorferi-infected mice, while only weak expression of VAP-1 was detected in uninfected mice.Conclusions: The present study showed that 68Ga-DOTA-Siglec-9 can detect B. burgdorferi infection-induced arthritis in mice. Furthermore, longitudinal PET/CT imaging allowed monitoring of arthritis development over time

Imaging of αvβ3 integrin expression in experimental myocardial ischemia with [68Ga]NODAGA-RGD positron emission tomography

Abstract Background Radiolabeled RGD peptides detect αvβ3 integrin expression associated with angiogenesis and extracellular matrix remodeling after myocardial infarction. We studied whether cardiac positron emission tomography (PET) with [68Ga]NODAGA-RGD detects increased αvβ3 integrin expression after induction of flow-limiting coronary stenosis in pigs, and whether αvβ3 integrin is expressed in viable ischemic or injured myocardium. Methods We studied 8 Finnish landrace pigs 13 ± 4 days after percutaneous implantation of a bottleneck stent in the proximal left anterior descending coronary artery. Antithrombotic therapy was used to prevent stent occlusion. Myocardial uptake of [68Ga]NODAGA-RGD (290 ± 31 MBq) was evaluated by a 62 min dynamic PET scan. The ischemic area was defined as the regional perfusion abnormality during adenosine-induced stress by [15O]water PET. Guided by triphenyltetrazolium chloride staining, tissue samples from viable and injured myocardial areas were obtained for autoradiography and histology. Results Stent implantation resulted in a partly reversible myocardial perfusion abnormality. Compared with remote myocardium, [68Ga]NODAGA-RGD PET showed increased tracer uptake in the ischemic area (ischemic-to-remote ratio 1.3 ± 0.20, p = 0.0034). Tissue samples from the injured areas, but not from the viable ischemic areas, showed higher [68Ga]NODAGA-RGD uptake than the remote non-ischemic myocardium. Uptake of [68Ga]NODAGA-RGD correlated with immunohistochemical detection of αvβ3 integrin that was expressed in the injured myocardial areas. Conclusions Cardiac [68Ga]NODAGA-RGD PET demonstrates increased myocardial αvβ3 integrin expression after induction of flow-limiting coronary stenosis in pigs. Localization of [68Ga]NODAGA-RGD uptake indicates that it reflects αvβ3 integrin expression associated with repair of recent myocardial injury

Noninvasive and Quantitative Monitoring of the Distributions and Kinetics of MicroRNA-Targeting Molecules in Vivo by Positron Emission Tomography

MicroRNAs (miRNAs) are endogenous, small, noncoding ribonucleic acids (RNAs) that bind to the 3' untranslated regions of messenger RNAs (mRNAs) and induce translational repression or mRNA degradation. Although numerous studies have reported that miRNAs are of potential use for disease diagnostics and gene therapy, little is known about their fates in vivo. This study elucidated the whole-body distributions and kinetics of intravenously administered miRNA-targeting molecules in vivo by positron emission tomography (PET) imaging. A 22-mer sequence targeting miR-1513 was conjugated with three different chelators and labeled with gallium-68 (Ga-68). These tracers were compared with a scrambled 22-mer sequence; 22-mer with two single base substitutions; anti-miR-34 22-mer; hexathymidylate (T-6), a 6-mer sequence; and an unconjugated chelator. miR-15b was chosen as a target because it is important for bone remodeling. All three Ga-68-labeled anti-miR-15b molecules had similar biodistributions and kinetics, and they all accumulated in the bones, kidneys, and liver. The bone accumulation of these tracers was the highest in the epiphyses of long tubular bones, maxilla, and mandible. By contrast, the scrambled 22-mer sequence, the 6-mer, and the unconjugated chelator did not accumulate in bones. PET imaging successfully elucidated the distributions and kinetics of Ga-68-labeled chelated miRNA-targeting molecules in vivo. This approach is potentially useful to evaluate new miRNA-based drugs

68Ga-DOTA-E[c(RGDfK)]2 Positron Emission Tomography Imaging of SHARPIN-Regulated Integrin Activity in Mice

Sharpincpdm mice demonstrated increased integrin activity and vascularization in B16-F10-luc melanoma tumors, as demonstrated by RGD-based in vivo PET imaging. These data indicate that SHARPIN, a protein previously associated with increased cancer growth and metastasis, may also have important regulatory roles in controlling the tumor microenvironment

Value of Ga-68-labeled bombesin antagonist (RM2) in the detection of primary prostate cancer comparing with [F-18]fluoromethylcholine PET-CT and multiparametric MRI-a phase I/II study

Objectives The bombesin derivative RM2 is a GRPr antagonist with strong binding affinity to prostate cancer (PCa). In this study, the impact of [Ga-68]Ga-RM2 positron emission tomography-computed tomography (PET-CT) for the detection of primary PCa was compared with that of [F-18]FCH PET-CT and multiparametric magnetic resonance imaging (mpMRI).Methods This phase I/II study was conducted in 30 biopsy-positive PCa subjects. The patients were stratified into high (10 patients), intermediate (10 patients), and low risk (10 patients) for extraglandular metastases as defined by National Comprehensive Cancer Network (NCCN) criteria (NCCN Clinical Practice Guidelines in Oncology, 2016). The prostate gland was classified in 12 anatomic segments for data analysis of the imaging modalities as well as histopathologic findings. The segment with the highest radiotracer uptake was defined as the "index lesion." All cases were scheduled to undergo prostatectomy with pelvic lymph node (LN) dissection in intermediate- and high-risk patients. Intraprostatic and pelvic nodal [Ga-68]Ga-RM2 and [F-18]FCH PET-CT findings were correlated with mpMRI and histopathologic results.Results Of the 312 analyzed regions, 120 regions (4 to 8 lesions per patient) showed abnormal findings in the prostate gland. In a region-based analysis, overall sensitivity and specificity of [Ga-68]Ga-RM2 PET-CT in the detection of primary tumor were 74% and 90%, respectively, while it was 60% and 80% for [F-18]FCH PET-CT and 72% and 89% for mpMRI. Although the overall sensitivity of [Ga-68]Ga-RM2 PET-CT was higher compared to that of [F-18]FCH PET-CT and mpMRI, the statistical analysis showed only significant difference between [Ga-68]Ga-RM2 PET-CT and [F-18]FCH PET-CT in the intermediate-risk group (p = 0.01) and [Ga-68]Ga-RM2 PET-CT and mpMRT in the high-risk group (p = 0.03). In the lesion-based analysis, there was no significant difference between SUVmax of [Ga-68]Ga-RM2 and [F-18]FCH PET-CT in the intraprostatic malignant lesions ([Ga-68]Ga-RM2: mean SUVmax: 5.98 +/- 4.13, median: 4.75; [F-18]FCH: mean SUVmax: 6.08 +/- 2.74, median: 5.5; p = 0.13).Conclusions [Ga-68]Ga-RM2 showed promising PET tracer for the detection of intraprostatic PCa in a cohort of patients with different risk stratifications. However, significant differences were only found between [Ga-68]Ga-RM2 PET-CT and [F-18]FCH PET-CT in the intermediate-risk group and [Ga-68]Ga-RM2 PET-CT and mpMRT in the high-risk group. In addition, GRP-R-based imaging seems to play a complementary role to choline-based imaging for full characterization of PCa extent and biopsy guidance in low- and intermediate-metastatic-risk PCa patients and has the potential to discriminate them from those at higher risks.</p

Glucagon-like peptide-1 receptor expression after myocardial infarction: Imaging study using [68Ga]NODAGA-exendin-4 positron emission tomography

BACKGROUND: Activation of glucagon-like peptide-1 receptor (GLP-1R) signaling protects against cardiac dysfunction and remodeling after myocardial infarction (MI). The aim of the study was to evaluate 68Ga-NODAGA-exendin-4 positron emission tomography (PET) for assessment of GLP-1R expression after MI in rats.METHODS AND RESULTS: Rats were studied at 3 days, 1 and 12 weeks after permanent coronary ligation or a sham-operation. Rats were injected with 68Ga-NODAGA-exendin-4 and scanned with PET and contrast-enhanced computed tomography (CT) followed by digital autoradiography and histology of left ventricle tissue sections. 68Ga-NODAGA-exendin-4 PET/CT showed focally increased tracer uptake in the infarcted regions peaking at 3 days and continuing at 1 week after MI. Pre-treatment with an unlabeled exendin-4 peptide significantly reduced 68Ga-NODAGA-exendin-4 uptake. By autoradiography, 68Ga-NODAGA-exendin-4 uptake was 8.6-fold higher in the infarcted region and slightly increased also in the remote, non-infarcted myocardium at 1 week and 12 weeks post-MI compared with sham. Uptake of 68Ga-NODAGA-exendin-4 correlated with the amount of CD68-positive macrophages in the infarcted area and alpha-smooth muscle actin staining in the remote myocardium.CONCLUSIONS: 68Ga-NODAGA-exendin-4 PET detects up-regulation of cardiac GLP-1R expression during healing of MI in rats and may provide information on the activated repair mechanisms after ischemic myocardial injury.</p

Targeting of vascular adhesion protein-1 by positron emission tomography visualizes sites of inflammation in Borrelia burgdorferi-infected mice

Abstract Background In the present study, we sought to evaluate the feasibility of targeting vascular adhesion protein-1 (VAP-1) by positron emission tomography (PET) for the longitudinal quantitative assessment of Borrelia burgdorferi infection-induced inflammation in mice. Methods Mice with B. burgdorferi infection-induced arthritis were studied. During a 7-week follow-up period, the progression of arthritis was monitored weekly with 68Ga-DOTA-Siglec-9 PET/computed tomography (CT) and measurement of tibiotarsal joint swellings. A subgroup of infected mice was treated with ceftriaxone. Finally, histopathological assessment of joint inflammation was performed and VAP-1 expression in joints were determined. Results Explicit joint swelling and 68Ga-DOTA-Siglec-9 uptake could be demonstrated in the affected joints from B. burgdorferi-infected mice. By contrast, no obvious accumulation of 68Ga-DOTA-Siglec-9 was detected in joints of uninfected mice. The maximum swelling and highest uptake in the affected joints were observed 4 weeks after the infection. 68Ga-DOTA-Siglec-9 uptake in joints correlated with joint swelling (P < 0.0001) and histopathological scoring of inflammation (P = 0.020). Despite short-term antibiotic treatment, the arthritis persisted, and the PET signal remained as high as in nontreated mice. Immunohistochemistry revealed strong-to-moderate expression of VAP-1 in the synovium of B. burgdorferi-infected mice, while only weak expression of VAP-1 was detected in uninfected mice. Conclusions The present study showed that 68Ga-DOTA-Siglec-9 can detect B. burgdorferi infection-induced arthritis in mice. Furthermore, longitudinal PET/CT imaging allowed monitoring of arthritis development over time