From Bench to Bedside-The Bad Berka Experience With First-in-Human Studies.

Precision oncology is being driven by rapid advances in novel diagnostics and therapeutic interventions, with treatments targeted to the needs of individual patients on the basis of genetic, biomarker, phenotypic, or psychosocial characteristics that distinguish a given patient from other patients with similar clinical presentations. Inherent in the theranostics paradigm is the assumption that diagnostic test results can precisely determine whether an individual is likely to benefit from a specific treatment. As part and integral in the current era of precision oncology, theranostics in the context of nuclear medicine aims to identify the appropriate molecular targets in neoplasms (diagnostic tool), so that the optimal ligands and radionuclides (therapeutic tool) with favorable labeling chemistry can be selected for personalized management of a specific disease, taking into consideration the specific patient, and subsequently monitor treatment response. Over the past two decades, the use of gallium-68 labeled peptides for somatostatin receptor (SSTR)-targeted PET/CT (or PET/MRI) imaging followed by lutetium-177 and yttrium-90 labeled SSTR-agonist for peptide receptor radionuclide therapy has demonstrated remarkable success in the management of neuroendocrine neoplasms, and paved the way to other indications of theranostics. Rapid advances are being made in the development of other peptide-based radiopharmaceuticals, small molecular-weight ligands and with newer radioisotopes with more favorable kinetics, potentially useful for theranostics strategies for the clinical application. The present review features the Bad Berka experience with first-in-human studies of new radiopharmaceuticals, for example, prostate-specific membrane antigen ligand, gastrin-releasing peptide receptor, neurotensin receptor 1 ligand, novel SSTR-targeting peptides and nonpeptide, and bone-seeking radiopharmaceuticals. Also new radioisotopes, for example, actinium (225Ac), copper (64Cu), scandium (44Sc), and terbium (152Tb/161Tb) will be discussed briefly demonstrating the development from basic science to precision oncology in the clinical setting.

[68Ga]Pentixafor PET/MR imaging of chemokine receptor 4 expression in the human carotid artery.

PURPOSE: Type 4 chemokine receptor (CXCR4) plays an important role in immune cell migration during the atherosclerosis progression. We aimed to evaluate [68Ga]Pentixafor positron emission tomography (PET) in combination magnetic resonance imaging (MRI) for in vivo quantification of CXCR4 expression in carotid plaques. METHODS: Seventy-two patients with lymphoma were prospectively scheduled for whole body [68Ga]Pentixafor PET/MRI with an additional T2-weighted carotid sequence. Volumes of interest (VOIs) were drawn along the carotid bifurcation regions, and the maximum tissue-to-blood ratios (TBR) of [68Ga]Pentixafor uptake were calculated. Lesions were categorized into non-eccentric (n = 27), mild eccentric (n = 67), moderately (n = 41) and severely (n = 19) eccentric carotid atherosclerosis. A different cohort of symptomatic patients (n = 10) with carotid stenosis scheduled for thrombendarterectomy (TEA) was separately imaged with 3T MRI with dedicated plaque sequences (time of flight, T1-, and T2-weighted). MRI findings were correlated with histochemical assessment of intact carotid plaques. RESULTS: At hybrid PET/MRI, we observed significantly increased [68Ga]Pentixafor uptake in mildly (mean TBRmax = 1.57 ± 0.27, mean SUVmax = 2.51 ± 0.39), moderately (mean TBRmax = 1.64 ± 0.37, mean SUVmax = 2.61 ± 0.55) and severely eccentric carotids (mean TBRmax = 1.55 ± 0.26, mean SUVmax = 2.40 ± 0.44) as compared to non-eccentric carotids (mean TBRmax = 1.29 ± 0.21, mean SUVmax = 1.77 ± 0.42) (p ≤ 0.05). Histological findings from TEA confirmed that prominent CXCR4 expression was localized within inflamed atheromas and preatheromas. Co-localization of cellular CXCR4 and CD68 expression in the plaque was observed by immunofluorescence staining. CONCLUSIONS: In vivo evaluation of CXCR4 expression in carotid atherosclerotic lesions is feasible using [68Ga]Pentixafor PET/MRI. In atherosclerotic plaque tissue, CXCR4 expression might be used as a surrogate marker for inflammatory atherosclerosis.

Immunohistochemical detection of chemokine receptor 4 expression in chronic osteomyelitis confirms specific uptake in 68Ga-Pentixafor-PET/CT.

Previous findings of our group showed the chemokine receptor CXCR4 as a suitable target in PET/CT-imaging of axial bone infections, early postoperative osteomyelitis and periprosthetic infections. The aim of this study was to verify specific uptake of 68Ga-Pentixafor in chronic osteomyelitis. METHODS: 29 consecutive patients who underwent 68Ga-Pentixafor-PET/CT with clinically suspected osteomyelitis were evaluated retrospectively. Bone tissues of 6 patients were available and evaluated by immunohistochemical staining for CXCR4 and autoradiography with 68Ga-Pentixafor. Staining was performed with an anti-CXCR4 antibody. In order to detect lymphocytic infiltration and CXCR4-expressing lymphocytes double immunofluorescence with an anti-CD3 and anti-CXCR4 antibody was performed. RESULTS: 68Ga-Pentixafor-PET/ CT was true positive in 16 and true negative in 13 patients. In available bone tissue samples, immunohistochemical staining of CXCR4 expression and autoradiography with 68Ga-Pentixafor was highly positive. Double immunofluorescence was able to detect CXCR4-expressing T-lymphocytes within all bone samples while a control sample of noninfected tibial bone was negative for CXCR4. CONCLUSION: 68Ga-Pentixafor-PET/CT specifically shows CXCR4-expressing immune cells in chronic osteomyelitis and is therefore a suitable method for imaging chronic infection of the skeleton.Der Chemokinrezeptor CXCR4 konnte in einer Pilotstudie unserer Arbeitsgruppe als geeignete Zielstruktur zur PET/CT-Bildgebung von frühen postoperativen und periprothetischen Osteomyelitiden sowie Osteomyelitiden im Stammskelett identifiziert werden. In dieser Studie haben wir untersucht, ob 68Ga-Pentixafor spezifisch CXCR4-exprimierende Entzündungszellen in einer chronischen Osteomyelitis darstellen kann. METHODEN: Es erfolgte eine retrospektive Auswertung von 29 Patienten mit klinischem Verdacht einer chronischen Osteomyelitis, die mittels 68Ga-Pentixafor-PET/CT untersucht wurden. Hiervon lagen uns in 6 Fällen Knochengewebe zur immunhistochemischen und autoradiographischen Evaluation vor. Die Immunhistochemie wurde mit einem anti-CXCR4 Antikörper durchgeführt. Des Weiteren wurden ein anti-CD3 und der anti-CXCR4-Antikörper zur Detektion CXCR4-exprimierender Lymphozyten am Ort der Entzündung mittels Doppel- Immunfluoreszenz verwendet. ERGEBNISSE: Die 68Ga-Pentixafor-PET/CT war bei 16 Patienten richtig positiv und bei 13 Patienten richtig negativ. Die Färbungen der verfügbaren Knochenpräparate waren sowohl in der Immunhistochemie als auch in der Autoradiographie deutlich positiv. In der Immunfluoreszenz konnten zudem CXCR4-exprimierende Lymphozyten am Ort der Entzündung in allen Proben nachgewiesen werden. Die Kontrolle eines Präparats einer nicht infizierten distalen Tibia zeigte dagegen keine CXCR4-oder CD3-Expression. FAZIT: Mit der 68Ga-Pentixafor-PET/CT können spezifisch CXCR4-exprimierende Lymphozyten am Ort der Entzündung nachgewiesen werden. Die 68Ga-Pentixafor-PET/CT stellt eine geeignete Methode in der Diagnostik chronischer Osteomyeltiden dar.

[68Ga]Pentixafor-PET/MRI for the detection of Chemokine receptor 4 expression in atherosclerotic plaques.

PURPOSE: The expression of chemokine receptor type 4 (CXCR4) was found co-localized with macrophages on the atherosclerotic vessel wall and participated in the initial emigration of leukocytes. Gallium-68 [68Ga]Pentixafor has recently been introduced for the imaging of atherosclerosis by targeting CXCR4. We sought to evaluate human atherosclerotic lesions using [68Ga]Pentixafor PET/MRI. METHODS: Thirty-eight oncology patients underwent [68Ga]Pentixafor PET/MR imaging at baseline. Maximum standardized uptake values (SUVmax) were derived from hot lesions in seven arterial segments and target-to-blood ratios (TBR) were calculated. ANOVA post-hoc and paired t test were performed for statistical comparison, Spearman's correlation coefficient between uptake ratios and cardiovascular risk factors were assessed. The reproducibility of [68Ga]Pentixafor PET/MRI was assessed in seven patients with a follow-up exanimation by Pearson's regression and Bland-Altman plots analysis. RESULTS: Thirty-four of 38 patients showed 611 focal [68Ga]Pentixafor uptake that followed the contours of the large arteries. Both prevalence and mean TBRmax were highest in the descending aorta. There were significantly higher TBR values found in men (1.9 ± 0.3) as compared to women (1.7 ± 0.2; p < 0.05). Patients with mean TBRmax > 1.7 showed a significantly higher incidence of diabetes, hypertension hypercholesterolemia and history of cardiovascular disease than patients with mean TBRmax ≤ 1.7. [68Ga]Pentixafor uptake showed a good reproducibility (r = 0.6, p < 0.01), and there was no difference between the mean TBRmax values of plaque lesions (TBRbaseline1.8 ± 0.3 vs TBRfollow-up1.8 ± 0.3) (p = 0.9). CONCLUSION: Patients with high arterial uptake showed increased incidence of cardiovascular risk factors, suggesting a potential role of [68Ga]Pentixafor in characterization of atherosclerosis.

68Ga-Pentixafor PET/CT Imaging of Chemokine Receptor CXCR4 in Chronic Infection of the Bone: First Insights.

Because of its role in infection and inflammatory processes, the chemokine receptor CXCR4 might be a potent target in imaging of infectious and inflammatory diseases. The aim of this pilot study was to determine whether the CXCR4 ligand 68Ga-pentixafor is suitable for imaging chronic infection of the bone. Methods: The study comprised 14 patients with suspected infection of the skeleton who underwent 68Ga-pentixafor PET/CT between April 2015 and February 2017 in our facility. 68Ga-pentixafor PET/CT results were retrospectively evaluated against a histologic, bacteriologic, and clinical standard. The results were also compared with available bone scintigraphy, white blood cell scintigraphy, and 18F-FDG PET/CT results. Results:68Ga-pentixafor PET/CT was positive in 9 of 14 patients. Diagnoses included osteitis or osteomyelitis of peripheral bone, osteomyelitis of the maxilla, and infected endoprostheses. Target-to-background ratios were 5.1-15 (mean, 8.7). Eight of 9 cases were true-positive as confirmed by pathology, bacteriology, or clinical observation. All negative cases were confirmed as true-negative by other imaging modalities and follow-up. Conclusion: Imaging of CXCR4 expression with 68Ga-pentixafor PET/CT appears suitable for diagnosing chronic infection of the skeleton. The findings of this study reveal a possible diagnostic gain in suspected chronic infections that are difficult to diagnose by other imaging modalities.

[68Ga]pentixafor for CXCR4 imaging in a PC-3 prostate cancer xenograft model - comparison with [18F]FDG PET/CT, MRI and ex vivo receptor expression.

PURPOSE: The aim was to characterize the properties of [68Ga]Pentixafor as tracer for prostate cancer imaging in a PC-3 prostate cancer xenograft mouse model and to investigate its correlation with [18F]FDG PET/CT, magnetic resonance imaging (MRI) and ex vivo analyses. METHODS: Static [68Ga]Pentixafor and [18F]FDG PET as well as morphological/ diffusion weighted MRI and 1H MR spectroscopy was performed. Imaging data were correlated with ex vivo biodistribution and CXCR4 expression in PC-3 tumors (immunohistochemistry (IHC), mRNA analysis). Flow cytometry was performed for evaluation of localization of CXCR4 receptors (in vitro PC-3 cell experiments). RESULTS: Tumor uptake of [68Ga]Pentixafor was significantly lower compared to [18F]FDG. Ex vivo CXCR4 mRNA expression of tumors was shown by PCR. Only faint tumor CXCR4 expression was shown by IHC (immuno reactive score of 3). Accordingly, flow cytometry of PC-3 cells revealed only a faint signal, cell membrane permeabilisation showed a slight signal increase. There was no significant correlation of [68Ga]Pentixafor tumor uptake and ex vivo receptor expression. Spectroscopy showed typical spectra of prostate cancer. CONCLUSION: PC-3 tumor uptake of [68Ga]Pentixafor was existent but lower compared to [18F]FDG. No significant correlation of ex vivo tumor CXCR4 receptor expression and [68Ga]Pentixafor tumor uptake was shown. CXCR4 receptor expression on the surface of PC-3 cells was existent but rather low possibly explaining the limited [68Ga]Pentixafor tumor uptake; receptor localization in the interior of PC-3 cells is presumable as shown by cell membrane permeabilisation. Further studies are necessary to define the role of [68Ga]Pentixafor in prostate cancer imaging.

Molecular Imaging of the Chemokine Receptor CXCR4 After Acute Myocardial Infarction.

OBJECTIVES: An assay for molecular imaging of myocardial CXCR4 expression was evaluated, in order to obtain mechanistic insights noninvasively based on quantitative positron emission tomography (PET). BACKGROUND: The chemokine receptor CXCR4 has emerged as a therapeutic target after acute myocardial infarction (AMI), because of its role in inflammatory and progenitor cell recruitment. METHODS: PET with the specific CXCR4 ligand, gallium-68 ((68)Ga)-pentixafor, was performed in mice (n = 53) and compared with ex vivo autoradiography, immunohistochemistry, and left ventricular flow cytometry. In addition, 12 patients were imaged at 2 to 8 days after AMI. RESULTS: In mice, (68)Ga-pentixafor identified regional CXCR4 upregulation in the infarct region, peaking at 3 days (infarct/remote [I/R] ratio 1.5 ± 0.2 at 3 days vs. 1.2 ± 0.3 at 7 days; p = 0.03), corresponding to a flow cytometry-based peak of CD45+ leukocytes and immunohistochemical detection of CD68+ macrophages and Ly6G+ granulocytes. Blockade with the CXCR4 antagonist AMD3100 abolished the signal. No specific uptake was found in sham-operated or control animals. Long-term treatment with oral enalapril attenuated the CXCR4 signal (I/R 1.2 ± 0.2 at 3 days and 1.0 ± 0.0.1 at 7 days; p = 0.01 vs. untreated). Patients showed variable degrees of CXCR4 upregulation in the infarct region. No single clinical parameter allowed for prediction of CXCR4 signal strength. At multivariate analysis, a combination of infarct size and time after reperfusion predicted the CXCR4 infarct signal (rmultiple = 0.73; p = 0.03). Infarct signal in the myocardium was paralleled by elevated pentixafor uptake in bone marrow (r = 0.61; p = 0.04), which highlighted systemic interactions. CONCLUSIONS: Targeted PET imaging with (68)Ga-pentixafor identifies the global and regional CXCR4 expression pattern in myocardium and systemic organs. CXCR4 upregulation after AMI coincides with inflammatory cell infiltration, but shows interindividual variability in patients. This may have implications for the response to CXCR4- or other inflammation-targeted therapy, and for subsequent ventricular remodeling.

MA-NOTMP: A Triazacyclononane Trimethylphosphinate Based Bifunctional Chelator for Gallium Radiolabelling of Biomolecules.

In the past few years, gallium-68 has demonstrated significant potential as a radioisotope for positron emission tomography (PET), and the optimization of chelators for gallium coordination is a major goal in the development of radiopharmaceuticals. Methylaminotriazacyclononane trimethylphosphinate (MA-NOTMP), a new C-functionalized triazacyclononane derivative with phosphinate pendant arms, presents excellent coordination properties for (68) Ga (low ligand concentration, labelling at low pH even at room temperature). A "ready-to-be-grafted" bifunctional chelating agent (p-NCS-Bz-MA-NOTMP) was prepared to allow (68) Ga labelling of sensitive biological vectors. Conjugation to a bombesin(7-14) derivative was performed, and preliminary in vitro experiments demonstrated the potential of MA-NOTMP in the development of radiopharmaceuticals. This new chelator is therefore of major interest for labelling sensitive biomolecules, and further in vivo experiments will soon be performed.

Assessment of alphavbeta3 integrin expression after myocardial infarction by positron emission tomography.

AIMS: The purpose of this study was to determine the feasibility of a new positron emission tomography (PET) imaging approach using an (18)F-labelled alpha(v)beta(3) integrin antagonist ((18)F-Galacto-RGD) to monitor the integrin expression after myocardial infarction. METHODS AND RESULTS: Male Wister rats were subjected to 20 min transient left coronary artery occlusion followed by reperfusion. Autoradiographic analysis and in vivo PET imaging were used to determine myocardial (18)F-Galacto-RGD uptake at different time points following reperfusion. RESULTS: PET imaging and autoradiography demonstrated no significant focal myocardial (18)F-Galacto-RGD uptake in non-operated control rats and at day 1 after reperfusion. However, focal accumulation in the infarct area started at day 3 (uptake ratio = 1.91 +/- 0.22 vs. remote myocardium), peaked between 1 (3.43 +/- 0.57) and 3 weeks (3.43 +/- 0.95), and decreased to 1.96 +/- 0.40 at 6 months after reperfusion. Pretreatment with alpha(v)beta(3) integrin antagonist c(-RGDfV-) significantly decreased tracer uptake, indicating the specificity of tracer uptake. The time course of focal tracer uptake paralleled vascular density as measured by CD31 immunohistochemical analysis. CONCLUSION: Regional (18)F-Galacto-RGD accumulation suggests up-regulation of alpha(v)beta(3) integrin expression after myocardial infarction, which peaks between 1 and 3 weeks and remains detectable until 6 months after reperfusion. This new PET tracer is promising for the monitoring of myocardial repair processes.

Gluc-Lys([18F]FP)-TOCA PET in patients with SSTR-positive tumors: biodistribution and diagnostic evaluation compared with [111In]DTPA-octreotide.

UNLABELLED: A recently developed (18)F-labeled PET tracer for somatostatin receptor (sstr) imaging, N(alpha)-(1-deoxy-D-fructosyl)-N(epsilon)-(2-[(18)F]fluoropropionyl)-Lys(0)-Tyr(3)-octreotate (Gluc-Lys([(18)F]FP)-TOCA), was evaluated in patients with sstr-positive tumors by assessing the pharmacokinetics, biodistribution, and diagnostic performance in comparison with [(111)In]DTPA-octreotide. METHODS: Twenty-five patients with different sstr-positive tumors were included in the study and were injected with 105 +/- 50 MBq Gluc-Lys([(18)F]FP)-TOCA. PET was performed up to 120 min with 2 different dynamic imaging protocols. Tracer kinetics in tumors and nontumor tissues and tumor-to-background ratios were described by region-of-interest analysis and standardized uptake values (SUVs). In 16 patients, sstr scintigraphy with [(111)In]DTPA-octreotide was performed (whole-body scans and SPECT). Two independent experts on PET and gamma- camera scans performed lesion counts. RESULTS: Gluc-Lys([(18)F]FP)-TOCA showed a fast and intense tumor accumulation as well as a rapid clearance from blood serum (biexponential elimination, with the half-lives of the initial and the terminal elimination phase calculated as t(1/2)(1) = 2.3 +/- 1.3 min and t(1/2)(2) = 26.4 +/- 14.6 min, respectively). Tumor-to-background ratios at 16 +/- 9 min and 34 +/- 12 min were as high as 80% and 90% (% of maximum ratios), respectively. Tumors showed high SUVs ranging from 13.7 +/- 2.3 (tumors in lung) up to 26.9 +/- 15.4 (abdominal tumors). Tracer distribution within tumor and nontumor tissues was stable up to 120 min (except spleen). No significant bowel activity was observed. Comparison of 29 tumors located in the liver showed a mean tumor-to-background ratio of 5.3 +/- 2.6 for Gluc-Lys([(18)F]FP)-TOCA vs. 4.6 +/- 3.3 for [(111)In]DTPA-octreotide (P = 0.24). Visual image analysis revealed a significantly higher number of lesions (factor of 2.4) and improved interobserver correlation (r = 0.99 vs. 0.86) for PET. CONCLUSION: Gluc-Lys([(18)F]FP)-TOCA PET allows a fast, high- contrast imaging of sstr-positive tumors. The biokinetics and diagnostic performance of Gluc-Lys([(18)F]FP)-TOCA are superior to [(111)In]DTPA-octreotide and-as far as can be derived from the literature-comparable with [(68)Ga]-DOTA-d Phe(1)-Tyr(3)-octreotide ([(68)Ga]DOTATOC).

Opioidergic activation in the medial pain system after heat pain.

Opioids modulate the affective component of pain and in vivo data indicate that opioids induce activation changes in the rostral ACC, insula and other brain areas. Hence, opioidergic release is to be expected in these brain regions following experimental pain stimulation. We examined healthy volunteers during heat pain and control subjects during rest using [18F]fluorodiprenorphine-PET. Pain stimulation led to significant reduction of diprenorphine binding in limbic and paralimbic brain areas including the rostral ACC and insula. The finding of altered opioidergic receptor availability in the rostral ACC after experimental nociceptive pain is novel and provides direct evidence for the involvement of this region in endogenous opioidergic inhibition of pain.

Quantification of [18F]diprenorphine kinetics in the human brain with compartmental and non-compartmental modeling approaches.

6-O-(2-[(18)F]fluoroethyl)-6-O-desmethyldiprenorphine ([(18)F]FDPN) is a nonselective opiate ligand that binds to postsynaptic micro, kappa and delta opiate receptors. Due to the longer half-life of F-18, compared to C-11, labeling DPN with F-18 allows for alternative experimental protocols and potentially the evaluation of endogenous opioid release. The applicability of this compound to assorted experimental protocols motivated the evaluation of [(18)F]FDPN kinetics with compartmental and non-compartmental models. The results indicate that a two-tissue compartmental model best characterizes the data obtained following a bolus injection of [(18)F]FDPN (120-min scanning protocol). Estimates of distribution volume (DV) were robust, being highly correlated for the one-tissue compartmental model as well as the invasive Logan model and the basis function method. Furthermore, the DV estimates were also stable under a shortened protocol of 60 min, showing a significant correlation with the full protocol. The binding potential (BP) values showed more variability between methods and in some cases were more sensitive to protocol length. In conclusion, this evaluation of [(18)F]FDPN kinetics illustrates that DV values can be estimated robustly using compartmental modeling, the basis function method or the invasive Logan modeling approach on a volume of interest level. BP values were also found to correlate with DV values; however, these results should be interpreted with the understanding that specific binding in the reference region (occipital region) may exist.