Dimeric RGD Research Articles

Targeted Magnetic Resonance Imaging/Near‐Infrared Dual‐Modal Imaging and Ferroptosis/Starvation Therapy of Gastric Cancer with Peritoneal Metastasis

AbstractAccurate identification and visualization of peritoneal metastases (PM) are clinically essential to improving the prognosis for gastric cancer. However, owing to the multifocal spread of peritoneal metastasis nodules, small size, and close contact with adjacent organs, identifying and completely removing them during surgery is extremely challenging, resulting in cancer treatment failure and recurrence. This study develops a T1‐weighted magnetic resonance imaging (MRI) contrast agent (FeGdNP)‐loaded indocyanine green/glucose oxidase (ICG/GOx) with conjugation of an RGD dimer (RGD2) and acid‐labile polymer mPEG (FeGdNP‐ICG/GOx‐RGD2‐mPEG). Compared with commercial Magnevist, the proposed FeGdNP‐ICG/GOx‐RGD2‐mPEG shows a two to three‐fold higher tumor ΔSNR in MRI of peritoneal metastasis and subcutaneous animal models. Compared with free ICG, the increased fluorescent signal of FeGdNP‐ICG/GOx‐RGD2‐mPEG allows for the detection of tiny tumor metastatic nodules (<3 mm), and the removal of the peritoneum transplanted tumors. Abundant gluconic acid and H2O2 are generated during the GOx‐mediated glucose depletion process in cancer cells, thereby enhancing Fenton reaction efficiency. Accumulated toxic ·OH can damage the mitochondrial function and induce the release of mitochondrial reactive oxygen species, which activates the ferroptosis pathway. The data indicate the potential of the nanoparticles for MRI preoperative diagnosis, intraoperative fluorescence‐guided navigation, and ferroptosis tumor therapy.

Intelligent Pore Switch of Hollow Mesoporous Organosilica Nanoparticles for High Contrast Magnetic Resonance Imaging and Tumor-Specific Chemotherapy.

Hollow mesoporous organosilica nanoparticles (HMONs) are widely considered as a promising drug nanocarrier, but the loaded drugs can easily leak from HMONs, resulting in the considerably decreased drug loading capacity and increased biosafety risk. This study reports the smart use of core/shell Fe3O4/Gd2O3 (FG) hybrid nanoparticles as a gatekeeper to block the pores of HMONs, which can yield an unreported large loading content (up to 20.4%) of DOX. The conjugation of RGD dimer (R2) onto the DOX-loaded HMON with FG capping (D@HMON@FG@R2) allowed for active tumor-targeted delivery. The aggregated FG in D@HMON@FG@R2 could darken the normal tissue surrounding the tumor due to the high r2 value (253.7 mM-1 s-1) and high r2/r1 ratio (19.13), and the intratumorally released FG as a result of reducibility-triggered HMON degradation could brighten the tumor because of the high r1 value (20.1 mM-1 s-1) and low r2/r1 ratio (7.01), which contributed to high contrast magnetic resonance imaging (MRI) for guiding highly efficient tumor-specific DOX release and chemotherapy.

Increased angiogenesis in thyroid tuberculosis identified by SPECT/CT based on RGD dimer radiotracer (99mTc-3PRGD2)

To evaluate the enterohepatic circulation of 75-Selenium turoselecolic acid (75Se-SeHCAT) during the first 3 h and its correlation with the abdominal retention at the 7th day (AR7), as contribution to the clinical study of biliar acid malabsorption (BAM).38 patients with chronic diarrhea were retrospectively studied. Acquisition protocol included static abdominal images at 1st, 2nd and 3rd hour and the 7th day after oral administration of the radiopharmaceutical. Images of 1–3 h determined 5 patterns of enterohepatic circulation that, due to their location, were characterized as: 1) gallbladder 2−3 h, 2) gallbladder 3 h, 3) gallbladder-abdomen 2−3 h, 4) abdomen, 5) upper left abdomen. The association of these patterns with the AR7 (Fisher, STATA) were investigated. Patients were classified as Non BAM (AR7 > 15%), mild-BAM (AR7 15−10%), moderate-BAM (AR7 10−5%) or severe-BAM (AR7 < 5%).19 patients had an AR7 diagnostic of BAM (7 mild-BAM, 5 moderate-BAM, 7 severe-BAM). The pattern “gallbladder at 2−3 h” was statistically associated with Non BAM (p 0,008), while “gallbladder-abdomen at 2−3 h” was correlated with having BAM (p 0,029).Variations detected at the abdominal level in images during the first 3 h were associated with changes in intestinal absorption and the incorporation of the radiopharmaceutical into the pool of bile acids, so visual interpretation of the images at 2nd and 3rd hour could be useful in the final assessment of the study.Evaluar la circulación enterohepática del ácido tauroselcólico marcado con 75-Selenio (75SeHCAT) durante las 3 primeras horas y su correlación con la retención abdominal al 7º día (RA7), como aportación al estudio clínico de malabsorción de ácidos biliares (MAB).Se estudiaron de forma retrospectiva 38 pacientes con diarrea crónica. El protocolo de adquisición incluyó imágenes estáticas abdominales a la 1ª, 2ª y 3ª hora y al 7º día tras la administración oral del radiofármaco. Las imágenes de 1 a 3 horas determinaron 5 patrones de circulación enterohepática que por su localización se caracterizaron como: 1) vesícula biliar 2−3 horas, 2) vesícula biliar 3 horas, 3) vesícula biliar-abdomen 2−3 horas, 4) abdomen y 5) abdomen superior izquierdo. Se investigó la asociación de estos patrones con la RA7 (Fisher-STATA). Los pacientes se clasificaron como No MAB (RA7 > 15%), MAB-leve (RA7 15−10%), MAB-moderado (RA7 10−5%) o MAB-grave (RA7 < 5%).19 pacientes presentaron una RA7 diagnóstica de MAB (7-leve, 5-moderada, 7-grave). El patrón “vesícula biliar a las 2−3 horas” se asoció estadísticamente con la No MAB (p 0,008), mientras que el de “vesícula biliar-abdomen a las 2-3 horas” se correlacionó con padecer MAB (p 0,029).Las variaciones detectadas a nivel abdominal en las imágenes durante las 3 primeras horas están asociadas a los cambios de absorción intestinal e incorporación del radiofármaco al pool de los ácidos biliares, por lo que la interpretación visual de las imágenes a la 2ª y 3ª hora podría tener utilidad en la valoración final del estudio.

SP-073 - Direct 18F-labeling of a dimeric RGD peptide via F-nucleophilic substitution on a phosphonate prothesis

SP-073 - Direct 18F-labeling of a dimeric RGD peptide via F-nucleophilic substitution on a phosphonate prothesis

A 64 Cu-porphyrin-based dual-modal molecular probe with integrin αv β3 targeting function for tumour imaging.

Pyropheophorbide-a (Pyro) is a promising multifunctional molecule for multimodal tumour imaging and photodynamic therapy, but its clinical applications are seriously restricted by the limited tumour accumulation capability. Here, we designed and synthesized a small-molecule probe that achieved specific dual-modal tumour imaging based on Pyro. Briefly, a novel molecule combining Pyro, an RGD dimer peptide (3PRGD2 ) and 64 Cu, was designed and synthesized, and the obtained molecule, 64 Cu-Pyro-3PRGD2 , exhibited high tumour specificity in both positron emission tomography and optical imaging in vivo. c (RGDfk) peptide blocking significantly reduced the efficacy of the probe, which confirmed the integrin αV β3 targeting of this molecular probe. 64 Cu-Pyro-3PRGD2 had very low accumulation in normal organs and could be rapidly cleared through kidney metabolism, which prevented the potential damage to adjacent normal tissues. Overall, combining tumour targeting, dual-modal imaging, and biosafety, 64 Cu-Pyro-3PRGD2 has the potential for clinical use as a molecular imaging probe for tumour diagnosis.

Small-sized gadolinium oxide based nanoparticles for high-efficiency theranostics of orthotopic glioblastoma

Glioblastoma (GBM) is one of the most malignant tumors with poor prognosis and outcomes. Although smaller particle size can lead to higher blood-brain barrier (BBB)-permeability of the nanomaterials, most of the reported BBB-crossable nanomaterials for targeted GBM therapy are larger than 24 nm. To realize theranostics of GBM, co-loading of therapeutic and diagnostic agents on the same nanomaterials further results in larger particle size. In this study, we developed a kind of novel BBB-transportable nanomaterials smaller than 14 nm for high-efficiency theranostics of GBM (i.e., high contrast magnetic resonance imaging (MRI) and radiosensitization of GBM). Typically, poly(acrylic acid) (PAA) stabilized extremely small gadolinium oxide nanoparticles with modification of reductive bovine serum albumin (ES-GON-rBSA) was synthesized in water phase, resulting in excellent water-dispersibility. RGD dimer (RGD2, Glu-{Cyclo[Arg-Gly-Asp-(D-Phe)-Lys]}2) and lactoferrin (LF) were then conjugated to the ES-GON-rBSA to obtain composite nanoparticle ES-GON-rBSA-LF-RGD2 with extraordinary relaxivities (r1 = 60.8 mM−1 s−1, r2/r1 = 1.1). The maximum signal enhancement (ΔSNR) for T1-weighted MRI of tumors reached up to 423 ± 42% at 12 h post-injection of ES-GON-rBSA-LF-RGD2, which is much higher than commercial Gd-chelates (<80%). ES-GON-rBSA-LF-RGD2 exhibited high biocompatibility and can transport across the in vitro BBB model and the in vivo BBB of mice due to its small particle size (dh = 13.4 nm) and LF receptor mediated transcytosis. Orthotopic GBM studies reinforce that ES-GON-rBSA3-LF-RGD2 can accumulate in the orthotopic GBM and enhance the radiation therapy of GBM as an effective radiosensitizing agent.

Exceedingly Small Gadolinium Oxide Nanoparticles with Remarkable Relaxivities for Magnetic Resonance Imaging of Tumors.

Gd chelates have occupied most of the market of magnetic resonance imaging (MRI) contrast agents for decades. However, there have been some problems (nephrotoxicity, non-specificity, and low r1 ) that limit their applications. Herein, a wet-chemical method is proposed for facile synthesis of poly(acrylic acid) (PAA) stabilized exceedingly small gadolinium oxide nanoparticles (ES-GON-PAA) with an excellent water dispersibility and a size smaller than 2.0 nm, which is a powerful T1 -weighted MRI contrast agent for diagnosis of diseases due to its remarkable relaxivities (r1 = 70.2 ± 1.8 mM-1 s-1 , and r2 /r1 = 1.02 ± 0.03, at 1.5 T). The r1 is much higher and the r2 /r1 is lower than that of the commercial Gd chelates and reported gadolinium oxide nanoparticles (GONs). Further ES-GON-PAA is developed with conjugation of RGD2 (RGD dimer) (i.e., ES-GON-PAA@RGD2) for T1 -weighted MRI of tumors that overexpress RGD receptors (i.e., integrin αv β3 ). The maximum signal enhancement (ΔSNR) for T1 -weighted MRI of tumors reaches up to 372 ± 56% at 2 h post-injection of ES-GON-PAA@RGD2, which is much higher than commercial Gd-chelates (<80%). Due to the high biocompatibility and high tumor accumulation, ES-GON-PAA@RGD2 with remarkable relaxivities is a promising and powerful T1 -weighted MRI contrast agent.

An improved kit formulation for one-pot synthesis of [99m Tc]Tc-HYNIC-E[c(RGDfK)]2 for routine clinical use in cancer imaging.

Radiolabeled Arg-Gly-Asp (RGD) peptide derivatives have immense potential for non-invasive monitoring of malignancies overexpressing integrin αv β3 receptors. Easy availability of suitable radiotracers would augment the utility of this class of molecular imaging agents. Towards this, the present article describes the development of an improved lyophilized kit for the routine clinical formulation of [99m Tc]Tc complex of HYNIC-conjugated dimeric cyclic RGD peptide derivative E-[c(RGDfK)]2 (E = glutamic acid, f = phenyl alanine, K = lysine) without using Sn2+ and systematic evaluation of its efficacy. Five batches of the kits were prepared, and [99m Tc]Tc-HYNIC-E[c(RGDfK)]2 radiotracer was synthesized with high radiochemical purity (98.6 ± 0.5%) and specific activity (124.8 GBq/μmol) using the kits. Biodistribution studies in C57BL/6 mice bearing melanoma tumor exhibited significant accumulation of the radiotracer in tumor (5.32 ± 0.56 %ID/g at 60 min p.i.), and this uptake was also found to be receptor-specific by blocking studies. Preliminary human clinical investigations carried out in 10 breast cancer patients revealed high radiotracer uptake in the tumor along with good tumor-to-background contrast. The developed kit formulation showed an exceptionally high shelf-life of at least 18 months. These results demonstrated promising attributes of the developed kit formulation and warrant more extensive clinical investigations.

68Ga-labeled dimeric and trimeric cyclic RGD peptides as potential PET radiotracers for imaging gliomas

68Ga-labeled cyclic RGD dimers and trimer were evaluated as PET radiotracers. It was found that the linker group had little impact on αvβ3 binding affinity of RGD dimers, which share similar αvβ3 binding affinity with the RGD trimer despite of their different multiplicity. Biodistribution properties of 68Ga radiotracers depend on RGD peptides and radiometal chelates. Among the 68Ga radiotracers evaluated, 68Ga-I2P-RGD2 has the best tumor uptake with good tumor-to-background ratios, and is a good PET radiotracer for imaging gliomas.

A dimeric bicyclic RGD ligand displays enhanced integrin binding affinity and strong biological effects on U-373 MG glioblastoma cells.

A C2-symmetric bicyclic peptide bearing two RGD motifs was developed as a dimeric ligand, and it displayed enhanced inhibition of ECM protein binding to purified integrin receptors as compared to monomeric RGD analogues. Moreover, the dimeric bicyclic ligand induced cell detachment and inhibited FAK phosphorylation in U-373 MG glioblastoma cells.

Fenton-Reaction-Acceleratable Magnetic Nanoparticles for Ferroptosis Therapy of Orthotopic Brain Tumors.

Cancer is one of the leading causes of morbidity and mortality in the world, but more cancer therapies are needed to complement existing regimens due to problems of existing cancer therapies. Herein, we term ferroptosis therapy (FT) as a form of cancer therapy and hypothesize that the FT efficacy can be significantly improved via accelerating the Fenton reaction by simultaneously increasing the local concentrations of all reactants (Fe2+, Fe3+, and H2O2) in cancer cells. Thus, Fenton-reaction-acceleratable magnetic nanoparticles, i.e., cisplatin (CDDP)-loaded Fe3O4/Gd2O3 hybrid nanoparticles with conjugation of lactoferrin (LF) and RGD dimer (RGD2) (FeGd-HN@Pt@LF/RGD2), were exploited in this study for FT of orthotopic brain tumors. FeGd-HN@Pt@LF/RGD2 nanoparticles were able to cross the blood-brain barrier because of its small size (6.6 nm) and LF-receptor-mediated transcytosis. FeGd-HN@Pt@LF/RGD2 can be internalized into cancer cells by integrin αvβ3-mediated endocytosis and then release Fe2+, Fe3+, and CDDP upon endosomal uptake and degradation. Fe2+ and Fe3+ can directly participate in the Fenton reaction, whereas the CDDP can indirectly produce H2O2 to further accelerate the Fenton reaction. The acceleration of Fenton reaction generates reactive oxygen species to induce cancer cell death. FeGd-HN@Pt@LF/RGD2 successfully delivered reactants involved in the Fenton reaction to the tumor site and led to significant inhibition of tumor growth. Finally, the intrinsic magnetic resonance imaging (MRI) capability of the nanoparticles was used to assess and monitor tumor response to FT (self-MRI monitoring).

Birnessite: A New‐Generation and Cost Effective Ion Exchange Material for Separation of Clinical‐Grade 90Y from 90Sr/90Y Mixture

AbstractThe widespread clinical utilization of 90Y for preparation of target specific radiopharmaceuticals stipulates design of superior advanced materials for facile and cost effective separation of 90Y. We demonstrate for the first time potential of birnessite type phylomanganates for radiochemical separation of clinical grade 90Y from 90Sr/90Y mixture. Sodium birnessite was synthesized by controlled oxidation of MnCl2.4H2O in presence of excess of NaOH and characterized thoroughly for structure, microstructure and purity. Ion exchange experiments in the presence of 90Sr/90Y equilibrium mixture confirmed the exceptionally high selectivity of synthetic sodium birnessite for exchanging Sr2+ ions and the conditions have been optimized to achieve radiochemically pure 90Y (&gt; 80% separation yield) meeting all the pharmaceutical requirements for its clinical use. Radionuclidic purity of 90Y could be achieved to &lt; 1 × 10−4 % of 90Sr which is well below the limit set internationally (2 × 10−3 %). The separated 90Y has been used to prepare 90Y radiolabeled 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid coupled dimeric cyclic RGD peptide derivative [DOTA−E[c(RGDfK)]2] and the biological efficacy of the radiotracer was established in C57/BL6 mice bearing melanoma tumors. The results indicated highly target specific radiotherapy suggesting the potential of sodium birnessite for cost effective radiochemical separation of 90Y.

Relationship Between Clinicopathological Characteristics and PET/CT Uptake in Esophageal Squamous Cell Carcinoma: [18F]Alfatide versus [18F]FDG.

To assess a novel radiotracer aluminum [18F]fluoride-1,4,7-triazacyclononane-triacetic acid-pegylated dimeric RGD ([18F]ALF-NOTA-PRGD2, denoted as [18F]Alfatide) for positron emission tomography (PET)/X-ray computed tomography (CT) and explore the relationships between clinicopathological characteristics and maximum standard uptake values in primary (SUVP) and metastatic lymph nodes (SUVLN) of patients with esophageal squamous cell carcinoma (ESCC), as verified by pathologic examination and compared with those obtained with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]DG) PET. We prospectively enrolled patients with newly diagnosed ESCC who agreed to undergo [18F]Alfatide PET/CT or [18F]FDG PET/CT scans before surgery at Shandong Cancer Hospital from May 2011 to July 2017. SUVs and the pathological tumor-node-metastasis (pTNM) stages of primary tumors and metastatic lymph nodes (LNs) were measured and confirmed pathologically. Immunohistochemical (IHC) staining for integrin αvβ3 was performed on tumor samples (both primary tumors and metastatic LNs) collected from nine patients. Of 61 patients who underwent PET/CT scans, 46 then underwent curative surgery and were included in our analysis (n = 21 for [18F]Alfatide PET/CT and n = 25 for [18F]FDG PET/CT). No significant differences in the SUVP on [18F]Alfatide PET/CT or [18F]FDG PET/CT were observed among the cohorts according to gender, pathological stage, T stage, status of LNs, and differentiation (all P > 0.05). The SUVLN differed significantly between the pathological stages and status of LNs both on [18F]Alfatide PET/CT (P = 0.03, 0.003) and [18F]FDG PET/CT (P = 0.001. < 0.001), but not according to gender (P = 0.128, 0.129), T stage (P = 0.791, 0.727), or tumor differentiation (P = 0.049, 0.053). Significant positive correlations were observed between the SUVLN on [18F]Alfatide PET/CT and [18F]FDG PET/CT, and pathological stage (r = 0.52, P = 0.016; r = 0.503, P = 0.01), LN status (r = 0.73, P < 0.001; r = 0.649, P < 0.001), and differentiation (r = 0.509, P < 0.019; r = 0.459, P = 0.021) were observed. No significant differences were found between the relationships of SUVP with SUVLN, length, age, gender, pathological stage, T stage, status of LN, or differentiation, or of SUVLN with length, age, gender, or T stage both on [18F]Alfatide PET/CT and [18F]FDG PET/CT (all P > 0.05). The quantitated expression levels of αvβ3 in primary tumors and metastatic LNs were 1.67 ± 1.12 and 3.42 ± 2.93, respectively (P = 0.031). Our results suggest that SUVLN is influenced by pathological stage, LN status, and differentiation. SUVLN may therefore serve as a new parameter for risk stratification of with ESCC patients. Moreover, [18F]Alfatide PET can provide complementary molecular information about ESCC metastasis.

Iminodiacetic acid as bifunctional linker for dimerization of cyclic RGD peptides

IntroductionIn this study, I2P-RGD2 was used as the example to illustrate a novel approach for dimerization of cyclic RGD peptides. The main objective of this study was to explore the impact of bifunctional linkers (glutamic acid vs. iminodiacetic acid) on tumor-targeting capability and excretion kinetics of the 99mTc-labeled dimeric cyclic RGD peptides. MethodsHYNIC-I2P-RGD2 was prepared by reacting I2P-RGD2 with HYNIC-OSu in the presence of diisopropylethylamine, and was evaluated for its αvβ3 binding affinity against 125I-echistatin bound to U87MG glioma cells. 99mTc-I2P-RGD2 was prepared with high specific activity (~185GBq/μmol). The athymic nude mice bearing U87MG glioma xenografts were used to evaluate its biodistribution properties and image quality in comparison with those of 99mTc-3P-RGD2. ResultsThe IC50 value for HYNIC-I2P-RGD2 was determined to be 39±6nM, which was very close to that (IC50=33±5nM) of HYNIC-3P-RGD2. Replacing glutamic acid with iminodiacetic acid had little impact on αvβ3 binding affinity of cyclic RGD peptides. 99mTc-I2P-RGD2 and 99mTc-3P-RGD2 shared similar tumor uptake values over the 2h period, and its αvβ3-specificity was demonstrated by a blocking experiment. The uptake of 99mTc-I2P-RGD2 was significantly lower than 99mTc-3P-RGD2 in the liver and kidneys. The U87MG glioma tumors were visualized by SPECT with excellent contrast using both 99mTc-I2P-RGD2 and 99mTc-3P-RGD2. ConclusionIminodiacetic acid is an excellent bifunctional linker for dimerization of cyclic RGD peptides. Bifunctional linkers have significant impact on the excretion kinetics of 99mTc radiotracers. Because of its lower liver uptake and better tumor/liver ratios, 99mTc-I2P-RGD2 may have advantages over 99mTc-3P-RGD2 for diagnosis of tumors in chest region.

Identification of Angiogenesis Rich-Viable Myocardium using RGD Dimer based SPECT after Myocardial Infarction.

Cardiac healing after myocardial ischemia is a complex biological process. Advances in understanding of wound healing response have paved the way for clinical testing of novel molecular imaging to improve clinical outcomes. A key factor for assessing myocardial viability after ischemic injury is the evaluation of angiogenesis accompanying increased expression of integrin αvβ3. Here, we describe the capability of an αvβ3 integrin-targeting SPECT agent, 99mTc-IDA-D-[c(RGDfK)]2, for identification of ischemic but viable myocardium, i.e., hibernating myocardium which is crucial to predict functional recovery after revascularization, the standard care of cardiovascular medicine. In vivo SPECT imaging of rat models with transient coronary occlusion showed significantly high uptake of 99mTc-IDA-D-[c(RGDfK)]2 in the ischemic region. Comparative measurements with 201Tl SPECT and 18F-FDG PET, then, proved that such prominent uptake of 99mTc-IDA-D-[c(RGDfK)]2 exactly matched the hallmark of hibernation, i.e., the perfusion-metabolism mismatch pattern. The uptake of 99mTc-IDA-D-[c(RGDfK)]2 was non-inferior to that of 18F-FDG, confirmed by time-course variation analysis. Immunohistochemical characterization revealed that an intense signal of 99mTc-IDA-D-[c(RGDfK)]2 corresponded to the vibrant angiogenic events with elevated expression of αvβ3 integrin. Together, these results establish that 99mTc-IDA-D-[c(RGDfK)]2 SPECT can serve as a sensitive clinical measure for myocardial salvage to identify the patients who might benefit most from revascularization.

Comparison of biological properties of 99mTc-labeled cyclic RGD Peptide trimer and dimer useful as SPECT radiotracers for tumor imaging

IntroductionThis study sought to evaluate a 99mTc-labeled trimeric cyclic RGD peptide (99mTc-4P-RGD3) as the new radiotracer for tumor imaging. The objective was to compare its biological properties with those of 99mTc-3P-RGD2 in the same animal model. MethodsHYNIC-4P-RGD3 was prepared by reacting 4P-RGD3 with excess HYNIC-OSu in the presence of diisopropylethylamine. 99mTc-4P-RGD3 was prepared using a kit formulation, and evaluated for its tumor-targeting capability and biodistribution properties in the BALB/c nude mice with U87MG human glioma xenografts. Planar and SPECT imaging studies were performed in athymic nude mice with U87MG glioma xenografts. For comparison purpose, 99mTc-3P-RGD2 (a αvβ3-targeted radiotracer currently under clinical evaluation for tumor imaging in cancer patients) was also evaluated in the same animal models. Blocking experiments were used to demonstrate the αvβ3 specificity of 99mTc-4P-RGD3. Results99mTc-4P-RGD3 was prepared with >95% RCP and high specific activity (~200GBq/μmol). 99mTc-4P-RGD3 and 99mTc-3P-RGD2 shared almost identical tumor uptake and similar biodistribution properties. 99mTc-4P-RGD3 had higher uptake than 99mTc-3P-RGD2 in the intestines and kidneys; but it showed better metabolic stability. The U87MG tumors were clearly visualized by SPECT with excellent contrast with 99mTc-4P-RGD3 and 99mTc-3P-RGD2. ConclusionIncreasing peptide multiplicity from 3P-RGD2 to 4P-RGD3 offers no advantages with respect to the tumor-targeting capability. 99mTc-4P-RGD3 is as good a SPECT radiotracer as 99mTc-3P-RGD2 for imaging αvβ3-positive tumors.

Preparation and bioevaluation of [99mTcN]2+-labeled tetrameric complex of E-c(RGDfK)2 as a radiotracer for imaging αvβ3 integrins in tumors

The objective of the present work is to radiolabel a dimeric RGD peptide namely, E-c(RGDfK)2 using [99mTcN]2+ core in order to obtain a 99mTc-labeled tetrameric RGD species, which is expected to have an enhanced tumor affinity. 99mTc-labeleld [E-c(RGDfK)2]2 complex was prepared with high radiochemical purity (>95 %). Pharmacokinetic evaluation of the radiolabeled agent, carried out in C57BL/6 mice bearing melanoma tumor, demonstrated good tumor uptake within 30 min of administration (3.94 ± 0.87 % IA/g) and retention therein till 3 h post-injection (2.65 ± 0.31 % IA/g). Blocking experiment revealed the specificity of the complex towards the αvβ3 receptors in the tumor model.

68Ga-BNOTA-PRGD2 PET/CT for evaluation of post-stroke angiogenesis: study protocol for a prospective open-label clinical trial

Background: Arginylglycylaspartic acid (RGD) is a tripeptide composed of L-arginine, glycine, and L-aspartic acid that shows great affinity for the integrin αv β3 receptor. A RGD dimer labeled with 68Ga, 68Ga-BNOTA-PRGD2 was designed for positron-emission tomography/computed tomography (PET/CT) imaging post-stroke angiogenesis, which has rarely been used in the clinic. We aimed to perform a prospective open-label trial to validate the diagnostic value of 68 Ga-BNOTA-PRGD2 PET/CT in post-stroke angiogenesis. Methods/Design: A self-controlled open-label clinical trial will be performed at the PET Center, Department of Nuclear Medicine, Peking Union Medical College Hospital, China. Fifty patients with stroke will undergo 68 Ga-BNOTA-PRGD2 PET/CT, 18 F-FDG PET/CT, and magnetic resonance imaging (MRI) at 2 weeks, 3 months, and 1 year after stroke onset. Primary outcomes include the standardized uptake value (SUV) in the cerebral infarction area and the standardized uptake value ratio of the injured side to the contralateral side detected by 68 Ga-BNOTA-PRGD2 PET/CT. Secondary outcomes include the safety of brain 68 Ga-BNOTA-PRGD2 PET/CT used to evaluate post-stroke angiogenesis. Discussion: Findings from this trial will provide important reference evidence for use of 68 Ga-BNOTA-PRGD2 PET/CT to evaluate post-stroke angiogenesis. Trial registration: ClinicalTrials.gov identifier: NCT01656785; registered on 1 August 2012.

Hybrid PET/optical imaging of integrin αVβ3 receptor expression using a (64)Cu-labeled streptavidin/biotin-based dimeric RGD peptide.

BackgroundHybrid PET/optical imaging provides quantitative and complementary information for diagnosis of tumors. Herein, we developed a 64Cu-labeled AlexaFluor 680-streptavidin ((AF)SAv)/biotin-based dimeric cyclic RGD peptide (RGD2) for hybrid PET/optical imaging of integrin αVβ3 expression.Methods64Cu-1,4,7,10-tetraazacyclododecane-N,N′,N′′,N′′′-tetraacetic acid (DOTA)-(AF)SAv/biotin-PEG-RGD2 was prepared by formation of a complex comprising DOTA-(AF)SAv and biotin-PEG-RGD2, followed by radiolabeling with 64Cu. Receptor binding studies of DOTA-(AF)SAv/biotin-PEG-RGD2 were performed using U87MG cells and 125I-RGDyK as the radioligand, and cellular uptake studies of 64Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 were also performed. MicroPET imaging followed by optical imaging of U87MG tumor-bearing mice was acquired after injection of the hybrid probe, and region of interest (ROI) analysis of tumors was performed. Ex vivo PET/optical imaging and biodistribution studies of the major tissues were performed after the in vivo imaging, and immunofluorescence staining of the tumor tissue sections was carried out.Results64Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 was prepared in 52.1 ± 5.4 % radiochemical yield and with specific activity of 1.0 ± 0.1 GBq/mg. Receptor binding studies showed that DOTA-(AF)SAv/biotin-PEG-RGD2 had higher binding affinity for integrin αVβ3 than RGD2, reflecting a possible polyvalency effect. Moreover, the hybrid probe revealed time-dependent uptake by U87MG cells. In a microPET/optical imaging study, the hybrid probe demonstrated high accumulation in tumors; ROI analysis revealed 2.7 ± 0.2 % ID/g at 1 h and 4.7 ± 0.2 % ID/g at 21 h after injection, and subsequently acquired optical images showed tumors with strong fluorescence intensity. Ex vivo PET/optical images of the major tissues confirmed the in vivo imaging data, and biodistribution studies demonstrated high and specific uptake in tumors (4.8 ± 0.1 % ID/g). Immunofluorescence staining showed the formation of new blood vessels in tumor tissues, suggesting that the tumor uptake was due to specific binding of the hybrid probe to integrin αVβ3 expressed on tumor cells.ConclusionsThese results indicate that a 64Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 is able to provide quantitative information on hybrid PET/optical imaging of integrin αVβ3 expression.

Toward realization of ‘mix-and-use’ approach in 68Ga radiopharmacy: preparation, evaluation and preliminary clinical utilization of 68Ga-labeled NODAGA-coupled RGD peptide derivative

IntroductionThe present article demonstrates a ‘mix-and-use’ approach for radiolabeling RGD peptide derivative with 68Ga, which is easily adaptable in hospital radiopharmacy practice. The radiotracer thus formulated was successfully used for positron emission tomography (PET) imaging of breast cancer in human patients. MethodsThe conditions for radiolabeling NODAGA-coupled dimeric cyclic RGD peptide derivative [NODAGA-(RGD)2] with 68Ga were optimized using 68Ga obtained from a 68Ge/68Ga generator developed in-house with CeO2-PAN composite sorbent as well as from a commercial 68Ge/68Ga generator obtained from ITG, Germany. Preclinical studies were carried out in C57BL/6 mice bearing melanoma tumors. The radiotracer was prepared in a hospital radiopharmacy using 68Ga obtained from ITG generator and used for monitoring breast cancer patients by positron emission tomography (PET) imaging. Results68Ga-NODAGA-(RGD)2 could be prepared with high radiolabeling yield (>98%) and specific activity (~50GBq/μmol) within 10min at room temperature by mixing 68Ga with the solution of the peptide conjugate. In vivo biodistribution studies showed significant uptake (5.24±0.39% ID/g) in melanoma tumor at 30min post-injection, with high tumor-to-background contrast. The integrin αvβ3 specificity of the tracer was corroborated by blocking study. Preliminary clinical studies in locally advanced breast cancer (LABC) patients indicated specifically high tumor uptake (SUVmax 10–15) with good contrast. ConclusionsThis is one of the very few reports which presents preliminary clinical data on use of 68Ga-NODAGA-(RGD)2 and the developed ‘mix-and-use’ holds tremendous prospect in clinical PET imaging using 68Ga.