The somatostatin receptor 2 antagonist 64Cu-NODAGA-JR11 outperforms 64Cu-DOTA-TATE in a mouse xenograft model

Copper-64 is an attractive radionuclide for PET imaging and is frequently used in clinical applications. The aim of this study was to perform a side-by-side comparison of the in vitro and in vivo performance of 64Cu-NODAGA-JR11 (NODAGA = 1,4,7-triazacyclononane,1-glutaric acid,4,7-acetic acid, JR11 = p-Cl-Phe-cyclo(D-Cys-Aph(Hor)-D-Aph(cbm)-Lys-Thr-Cys)D-Tyr-NH2), a somatostatin receptor 2 antagonist, with the clinically used sst2 agonist 64Cu-DOTA-TATE ((TATE = D-Phe-cyclo(Cys-Tyr-D-Trp-Lys-Thr-Cys)Thr). In vitro studies demonstrated Kd values of 5.7±0.95 nM (Bmax = 4.1±0.18 nM) for the antagonist 64/natCu-NODAGA-JR11 and 20.1±4.4. nM (Bmax = 0.48±0.18 nM) for the agonist 64/natCu-DOTA-TATE. Cell uptake studies showed the expected differences between agonists and antagonists. Whereas 64Cu-DOTA-TATE (the agonist) showed very effective internalization in the cell culture assay (with 50% internalized at 4 hours post-peptide addition under the given experimental conditions), 64Cu-NODAGA-JR11 (the antagonist) showed little internalization but strong receptor-mediated uptake at the cell membrane. Biodistribution studies of 64Cu-NODAGA-JR11 showed rapid blood clearance and tumor uptake with increasing tumor-to-relevant organ ratios within the first 4 hours and in some cases, 24 hours, respectively. The tumor washout was slow or non-existent in the first 4 hours, whereas the kidney washout was very efficient, leading to high and increasing tumor-to-kidney ratios over time. Specificity of tumor uptake was proven by co-injection of high excess of non-radiolabeled peptide, which led to >80% tumor blocking. 64Cu-DOTA-TATE showed less favorable pharmacokinetics, with the exception of lower kidney uptake. Blood clearance was distinctly slower and persistent higher blood values were found at 24 hours. Uptake in the liver and lung was relatively high and also persistent. The tumor uptake was specific and similar to that of 64Cu-NODAGA-JR11 at 1 h, but release from the tumor was very fast, particularly between 4 and 24 hours. Tumor-to-normal organ ratios were distinctly lower after 1 hour. This is indicative of insufficient in vivo stability. PET studies of 64Cu-NODAGA-JR11 reflected the biodistribution data with nicely delineated tumor and low background. 64Cu-NODAGA-JR11 shows promising pharmacokinetic properties for further translation into the clinic.

New Gastrin Releasing Peptide Receptor-Directed [99mTc]Demobesin 1 Mimics: Synthesis and Comparative Evaluation

We have previously reported on the gastrin releasing peptide receptor (GRPR) antagonist [^99mTc]1, ([^99mTc]demobesin 1, ^99mTc-[N₄'-diglycolate-dPhe⁶,Leu-NHEt¹³]BBN(6-13)). [^99mTc]1 has shown superior biological profile compared to analogous agonist-based ^99mTc-radioligands. We herein present a small library of [^99mTc]1 mimics generated after structural modifications in (a) the linker ([^99mTc]2, [^99mTc]3, [^99mTc]4), (b) the peptide chain ([^99mTc]5, [^99mTc]6), and (c) the C-terminus ([^99mTc]7 or [^99mTc]8). The effects of above modifications on the biological properties of analogs were studied in PC-3 cells and tumor-bearing SCID mice. All analogs showed subnanomolar affinity for the human GRPR, while most receptor-affine 4 and 8 behaved as potent GRPR antagonists in a functional internalization assay. In mice bearing PC-3 tumors, [^99mTc]1-[^99mTc]6 exhibited GRPR-specific tumor uptake, rapidly clearing from normal tissues. [^99mTc]4 displayed the highest tumor uptake (28.8 ± 4.1%ID/g at 1 h pi), which remained high even after 24 h pi (16.3 ± 1.8%ID/g), well surpassing that of [^99mTc]1 (5.4 ± 0.7%ID/g at 24 h pi).

Towards the first measurement of matter-antimatter gravitational interaction

The AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is a CERN based experiment with the central aim to measure directly the gravitational acceleration of antihydrogen. Antihydrogen atoms will be produced via charge exchange reactions which will consist of Rydberg-excited positronium atoms sent to cooled antiprotons within an electromagnetic trap. The resulting Rydberg antihydrogen atoms will then be horizontally accelerated by an electric field gradient (Stark effect), they will then pass through a moiré deflectometer. The vertical deflection caused by the Earth's gravitational field will test for the first time the Weak Equivalence Principle for antimatter. Detection will be undertaken via a position sensitive detector. Around 103 antihydrogen atoms are needed for the gravitational measurement to be completed. The present status, current achievements and results will be presented, with special attention toward the laser excitation of positronium (Ps) to the n=3 state and the production of Ps atoms in the transmission geometry.

Somatostatin Receptor Antagonists for Imaging and Therapy

Somatostatin receptor (sstr) scintigraphy for imaging and sstr analogs for treatment have been used for more than 20 y. An important improvement in recent years was the introduction of peptide receptor radionuclide therapy with radiolabeled sstr agonists, such as [⁹⁰Y-DOTA⁰,Tyr³]octreotide or [¹⁷⁷Lu-DOTA⁰,Tyr³]octreotide (⁹⁰Y- or ¹⁷⁷Lu-DOTATOC, respectively) and [¹⁷⁷Lu-DOTA⁰,Tyr³]octreotate (¹⁷⁷Lu-DOTATATE). PET/CT with ⁶⁸Ga-labeled sstr agonists, such as ⁶⁸Ga-DOTATOC, ⁶⁸Ga-DOTATATE, and [⁶⁸Ga-DOTA,1-Nal³]octreotide (⁶⁸Ga-DOTANOC), plays an important role in staging and restaging neuroendocrine tumors. Most importantly, sstr scintigraphy and sstr PET/CT can distinguish patients who will qualify for and benefit from peptide receptor radionuclide therapy. This characteristic of sstr targeting is important because it allows a personalized treatment approach (theranostic approach). Until recently, it was thought that internalization of the radiolabeled agonist was mandatory for sstr-mediated imaging and therapy. It was Ginj et al. who proposed in 2006 the paradigm shift that radiolabeled sstr antagonists may perform better than agonists despite the lack of internalization. Despite the rather limited number of head-to-head comparisons of sstr antagonists and agonists, the superiority of sstr antagonists was demonstrated in several cases. From a small library of sstr antagonists, the analog JR11 (Cpa-c[d-Cys-Aph(Hor)-d-Aph(Cbm)-Lys-Thr-Cys]-d-Tyr-NH₂), an antagonist with selectivity for sstr subtype 2, showed the best overall characteristics for sstr subtype 2 targeting and was therefore selected for clinical translation. JR11 is under clinical development as a PET imaging agent when labeled with ⁶⁸Ga (⁶⁸Ga-NODAGA-JR11 or ⁶⁸Ga-OPS202) and as a therapeutic agent when labeled with ¹⁷⁷Lu (¹⁷⁷Lu-DOTA-JR11 or ¹⁷⁷Lu-OPS201). In this article, we discuss the development and current status of radiolabeled sstr antagonists. Evidence based on preclinical work, on quantitative in vivo autoradiography of human tumor slices, and on human data now supports a shift to sstr antagonists.

Current Status of Radiopharmaceuticals for the Theranostics of Neuroendocrine Neoplasms

Nuclear medicine plays a pivotal role in the management of patients affected by neuroendocrine neoplasms (NENs). Radiolabeled somatostatin receptor analogs are by far the most advanced radiopharmaceuticals for diagnosis and therapy (radiotheranostics) of NENs. Their clinical success emerged receptor-targeted radiolabeled peptides as an important class of radiopharmaceuticals and it paved the way for the investigation of other radioligand-receptor systems. Besides the somatostatin receptors (sstr), other receptors have also been linked to NENs and quite a number of potential radiolabeled peptides have been derived from them. The Glucagon-Like Peptide-1 Receptor (GLP-1R) is highly expressed in benign insulinomas, the Cholecystokinin 2 (CCK2)/Gastrin receptor is expressed in different NENs, in particular medullary thyroid cancer, and the Glucose-dependent Insulinotropic Polypeptide (GIP) receptor was found to be expressed in gastrointestinal and bronchial NENs, where interestingly, it is present in most of the sstr-negative and GLP-1R-negative NENs. Also in the field of sstr targeting new discoveries brought into light an alternative approach with the use of radiolabeled somatostatin receptor antagonists, instead of the clinically used agonists. The purpose of this review is to present the current status and the most innovative strategies for the diagnosis and treatment (theranostics) of neuroendocrine neoplasms using a cadre of radiolabeled regulatory peptides targeting their receptors.

Crosstalk between E2f1 and c-Myc mediates hepato-protective effect of royal jelly on taxol-induced damages

Previous histopathological studies have shown the hepatotoxicity of paclitaxel (TXL). However, there is little known about the molecular pathway(s) of TXL-induced hepatotoxicity. Therefore, this study aimed to uncover the role of two transcription factors in the TXL-induced hepatotoxicity. Moreover, the hepato-protective effect of royal jelly (RJ) on TXL-induced toxicity was investigated. Wistar rats were divided into control and test groups. The test groups along with TXL received various doses of RJ (0, 50, 100 and 150 mg/kg, body weight). Biochemical hepatic functional assays, histopathological studies and hepatic superoxide dismutase level were determined. Additionally, the expression of E2f1 and cellular-myelocytomatosis (c-Myc) at messenger RNA (mRNA) level in the liver was evaluated. The hepatic functional biomarkers showed a significant ( p < 0.05) elevation in the TXL-received animals, while RJ administration for 28 days resulted in a remarkable reduction in TXL-elevated alkaline phosphatase, alanine transaminase and lactate dehydrogenase levels. The TXL-treated animals showed a significant ( p < 0.05) up-regulation of E2f1 and down-regulation of c-Myc at mRNA level, respectively. RJ lowered the expression of E2f1 while enhanced the expression of c-Myc in a dose-dependent manner. Our data suggest the hepato-protective effects of RJ on TXL-induced toxicity, which may attribute to a clear crosstalk between E2f1 and c-Myc as two regulators of liver growth.

Preoperative Glucagon-like peptide-1 receptor imaging reduces surgical trauma and pancreatic tissue loss in insulinoma patients: a report of three cases

Background

Insulinomas are rare tumors, in the majority of cases best treated by surgical resection. Preoperative localization of insulinoma is challenging. The more precise the preoperative localization the less invasive and safer is the resection. The purpose of the study is to check the impact of a new technique to localize insulinoma on the surgical strategy.

Findings

We present exact preoperative localization with Glucagon-like peptide-1 receptor (GLP-1R) imaging. This allows a more precise resection thereby reducing surgical access trauma, loss of healthy pancreatic tissue and increasing safety and quality of the surgical intervention.

Conclusion

With the help of precise preoperative localization of insulinoma with GLP-1R imaging the surgeon is able to minimize the amount of resected healthy pancreatic tissue. We hypothesize that GLP-1R imaging will become a preoperative diagnostic tool to be used for many patients scheduled for open or laparoscopic insulinoma resection.

Localization of Hidden Insulinomas with ⁶⁸Ga-DOTA-Exendin-4 PET/CT: A Pilot Study

(111)In-DOTA-exendin-4 SPECT/CT has been shown to be highly efficient in the detection of insulinomas. We aimed at determining whether novel PET/CT imaging with [Nle(14),Lys(40)(Ahx-DOTA-(68)Ga)NH2]exendin-4 ((68)Ga-DOTA-exendin-4) is feasible and sensitive in detecting benign insulinomas.

METHODS

(68)Ga-DOTA-exendin-4 PET/CT and (111)In-DOTA-exendin-4 SPECT/CT were performed in a randomized cross-over order on 5 patients with endogenous hyperinsulinemic hypoglycemia. The gold standard for comparison was the histologic diagnosis after surgery.

RESULTS

In 4 patients histologic diagnosis confirmed a benign insulinoma, whereas one patient refused surgery despite a positive (68)Ga-DOTA-exendin-4 PET/CT scan. In 4 of 5 patients, previously performed conventional imaging (CT or MR imaging) was not able to localize the insulinoma. (68)Ga-DOTA-exendin-4 PET/CT correctly identified the insulinoma in 4 of 4 patients, whereas (111)In-DOTA-exendin-4 SPECT/CT correctly identified the insulinoma in only 2 of 4 patients.

CONCLUSION

These preliminary data suggest that the use of (68)Ga-DOTA-exendin-4 PET/CT in detecting hidden insulinomas is feasible.

Does imaging αvβ3 integrin expression with PET detect changes in angiogenesis during bevacizumab therapy?

In recent years, there has been a growing interest in molecular imaging markers of tumor-induced angiogenesis. Several radiolabeled RGD (arginine, glycine, aspartate) peptides have been developed for PET imaging of αvβ3 integrins in the tumor vasculature, but there are only limited data on how angiogenesis inhibitors affect the tumor uptake of these peptides.

METHODS

Changes in (68)Ga-NODAGA-c(RGDfK) peptide uptake were measured using PET during bevacizumab therapy of 2 αvβ3-negative squamous cell carcinoma cell lines (A-431 and FaDu) that induce αvβ3-positive neovasculature when transplanted into nude mice. Tumor uptake of (68)Ga-NODAGA-c(RGDfK) was correlated to microvascular density, vascular morphology, and permeability as well as αvβ3 integrin expression.

RESULTS

Bevacizumab significantly inhibited growth of A-431 tumors and caused a significant reduction in microvascular density and αvβ3 integrin expression within 7 d after start of therapy. Bevacizumab also caused a normalization of blood vessel morphology and decreased tumor necrosis. However, (68)Ga-NODAGA-c(RGDfK) uptake was significantly increased at day 7 of therapy and did not decrease until after 3 wk of treatment. In Fadu xenografts, bevacizumab therapy caused only a minor inhibition of tumor growth and minor changes in (68)Ga-NODAGA-c(RGDfK) uptake.

CONCLUSION

Uptake of radiolabeled RGD peptides is not necessarily decreased by effective antiangiogenic therapy. Early in the course of therapy a decrease in the expression of αvβ3 integrins may not be reflected by a decrease in the uptake of RGD peptides.

Comparison of somatostatin receptor agonist and antagonist for peptide receptor radionuclide therapy: a pilot study

Preclinical and clinical studies have indicated that somatostatin receptor (sst)-expressing tumors demonstrate higher uptake of radiolabeled sst antagonists than of sst agonists. In 4 consecutive patients with advanced neuroendocrine tumors, we evaluated whether treatment with (177)Lu-labeled sst antagonists is feasible.

METHODS

After injection of approximately 1 GBq of (177)Lu-DOTA-[Cpa-c(DCys-Aph(Hor)-DAph(Cbm)-Lys-Thr-Cys)-DTyr-NH2] ((177)Lu-DOTA-JR11) and (177)Lu-DOTATATE, 3-dimensional voxel dosimetry analysis based on SPECT/CT was performed. A higher tumor-to-organ dose ratio for (177)Lu-DOTA-JR11 than for (177)Lu-DOTATATE was the prerequisite for treatment with (177)Lu-DOTA-JR11.

RESULTS

Reversible minor adverse effects of (177)Lu-DOTA-JR11 were observed. (177)Lu-DOTA-JR11 showed a 1.7-10.6 times higher tumor dose than (177)Lu-DOTATATE. At the same time, the tumor-to-kidney and tumor-to-bone marrow dose ratio was 1.1-7.2 times higher. All 4 patients were treated with (177)Lu-DOTA-JR11, resulting in partial remission in 2 patients, stable disease in 1 patient, and mixed response in the other patient.

CONCLUSION

Treatment of neuroendocrine tumors with radiolabeled sst antagonists is clinically feasible and may have a significant impact on peptide receptor radionuclide therapy.

Effect of a home bleaching agent on the fracture toughness of resin composites, using short rod design

STATEMENT OF PROBLEM

Resin composites are brittle materials and their major shortcomings are manifested in their sensitivity to flaws and defects. Although various mechanical properties of resin composites have been described, few studies are available on assessing the effect of bleaching agents on resin composites using the short rod design.

PURPOSE

To place various resin composites into distilled water at 37°C for 21 days and determine the effect of immersion time in distilled water, with and without exposure to 10% carbamide peroxide by employing short rod design fracture toughness test.

MATERIALS AND METHOD

Specimens were prepared from three resin composites; Rok (SDI), Esthet (Dentsply), and Estelite (Tokuyama). For each material, a total of 24 disc-shaped specimens were prepared using a custom-made mould. Specimens were randomly divided into 3 groups of 8 and conditioned in 37°C distilled water for either 24 hours, or 21 days. 21 day specimens were tested both with and without applying bleaching agent; Polanight (SDI). Study group specimens were bleached for 21 days, 2 hours a day. The specimens were loaded using a universal testing machine with a crosshead speed of 0.5 mm per minute. The maximum load at specimen failure was recorded and the KIc (MPa. M (0.5)) was calculated.

RESULTS

Statistical analysis using two-way ANOVA showed a significant relationship between material and time (p< 0.05).Tukey's test showed that after 24 h of immersion in distilled water, Rok revealed the highest KIc followed by Esthet and Estelite. The bleaching agent significantly improved the fracture toughness values of Esthet while it decreased that of Estelite.

CONCLUSION

The fracture toughness of the resin composites was affected by the bleaching agent and distilled water. In comparison with Rok and Estelite, fracture toughness of Esthet was increased due to aging and application of bleaching agent.

Radiopharmaceutical development of radiolabelled peptides

Receptor targeting with radiolabelled peptides has become very important in nuclear medicine and oncology in the past few years. The overexpression of many peptide receptors in numerous cancers, compared to their relatively low density in physiological organs, represents the molecular basis for in vivo imaging and targeted radionuclide therapy with radiolabelled peptide-based probes. The prototypes are analogs of somatostatin which are routinely used in the clinic. More recent developments include somatostatin analogs with a broader receptor subtype profile or with antagonistic properties. Many other peptide families such as bombesin, cholecystokinin/gastrin, glucagon-like peptide-1 (GLP-1)/exendin, arginine-glycine-aspartic acid (RGD) etc. have been explored during the last few years and quite a number of potential radiolabelled probes have been derived from them. On the other hand, a variety of strategies and optimized protocols for efficient labelling of peptides with clinically relevant radionuclides such as (99m)Tc, M(3+) radiometals ((111)In, (86/90)Y, (177)Lu, (67/68)Ga), (64/67)Cu, (18)F or radioisotopes of iodine have been developed. The labelling approaches include direct labelling, the use of bifunctional chelators or prosthetic groups. The choice of the labelling approach is driven by the nature and the chemical properties of the radionuclide. Additionally, chemical strategies, including modification of the amino acid sequence and introduction of linkers/spacers with different characteristics, have been explored for the improvement of the overall performance of the radiopeptides, e.g. metabolic stability and pharmacokinetics. Herein, we discuss the development of peptides as radiopharmaceuticals starting from the choice of the labelling method and the conditions to the design and optimization of the peptide probe, as well as some recent developments, focusing on a selected list of peptide families, including somatostatin, bombesin, cholecystokinin/gastrin, GLP-1/exendin and RGD.

Radiolabeled peptides: valuable tools for the detection and treatment of cancer

Human cancer cells overexpress many peptide receptors as molecular targets. Radiolabeled peptides that bind with high affinity and specificity to the receptors on tumor cells hold great potential for both diagnostic imaging and targeted radionuclide therapy. The advantage of solid-phase peptide synthesis, the availability of different chelating agents and prosthetic groups and bioconjugation techniques permit the facile preparation of a wide variety of peptide-based targeting molecules with diverse biological and tumor targeting properties. Some of these peptides, including somatostatin, bombesin, vasoactive intestinal peptide, gastrin, neurotensin, exendin and RGD are currently under investigation. It is anticipated that in the near future many of these peptides may find applications in nuclear oncology. This article presents recent developments in the field of small peptides, and their applications in the diagnosis and treatment of cancer.