The involvement of the pro-inflammatory cytokine, tumour necrosis factor alpha (TNF-α) and the sympathetic nervous system in the development of delayed-onset muscle soreness has not been established. I assessed the effect of etanercept, a TNF- α inhibitor, and atenolol, a β1-receptor antagonist, on DOMS induced in the quadriceps muscle. Thirteen male subjects reported to the exercise laboratory on three separate occasions, 6-15 weeks apart. In a randomised, double-blind cross-over format, I administered etanercept (25mg), atenolol (25mg) or placebo, one hour before the exercise. Subjects then completed four sets of 15 repetitions at 80% of their one repetition maximum (1RM) on a 45° inclined leg press machine. Muscle strength changes were detected by remeasuring the subject’s 1RM 24h, 48h and 72h after the exercise. Sensitivity to pressure of the quadriceps muscle was measured using a pressure algometer before and 24h, 48h and 72h after exercise. The subject’s perception of the pain was measured with the visual analogue scale and McGill Pain Questionnaire. Muscle tumour necrosis factor-alpha concentration was measured before exercise and then 2h and 24h after exercise in four subjects. Muscle strength was impaired 24h and 48h after exercise regardless of agent administered (P < 0.001). At 72h after exercise, muscle strength was significantly improved (P < 0.01) in subjects receiving etanercept and atenolol compared to those receiving placebo. The subject’s were significantly more sensitive to pressure applied to the quadriceps 24h, 48h and 72h after exercise compared to before exercise, regardless of agent administered (P < 0.001). The VAS was elevated significantly at all three time intervals, with no difference after etanercept or atenolol administration compared to that of placebo. There was no significant difference in the muscle TNF-α concentration between any of the time intervals or between subjects receiving placebo and etanercept (P=0.065). The administration of atenolol and etanercept, at the regimen used, had no effect on the soreness associated with DOMS.

Although all cells in a multicellular organism contain the same set of genes, the spatiotemporal expression of these genes needs to be dynamically regulated for morphogenesis and life cycle transitions to take place. Polycomb-group (PcG) proteins are evolutionarily-conserved epigenetic regulators that function – via epigenetic marks such as H3K27me3 and modifications to chromatin structure – to maintain the repression of developmentally-important genes so that these genes are only expressed in the appropriate cells at the appropriate times. This repressive activity of the PcG is antagonised by the trithorax-group (trxG) of proteins. Although they maintain specific patterns of gene repression, PcG proteins are ubiquitously expressed. How their activity is regulated is largely unknown. To identify such regulatory pathways, a genetic screen for modifiers of PcG activity in Arabidopsis was carried out previously using the PcG mutant curly leaf (clf), which has moderately-severe developmental defects due to the ectopic or untimely expression of developmental regulators such as floral homeotic genes and the important flowering time regulator FLOWERING LOCUS T (FT). I characterised three novel potential regulators identified in this genetic screen: the chromatin-associated protein AT-HOOK MOTIF NUCLEAR LOCALISED PROTEIN 22 (AHL22), the 26S proteasome and the novel trithorax-group members ANTAGONIST OF LHP1 1 and 2 (ALP1 and ALP2). I found that the dominant sop-11D mutation is caused by over expression of AHL22 which suppresses the phenotype of clf by reducing FT expression. However, genetic analysis suggests that AHL22 may act in a parallel pathway to the PcG. I showed that mutations affecting diverse subunits of the 26S proteasome reduce the mis-expression of CLF targets and suppress the phenotypes of clf although they do not restore H3K27me3 levels at these targets. Pharmacological inhibition of the proteasome also alleviated the mis-expression of target genes found in clf mutants. Analysis of PcG protein levels following proteasome inhibition suggests that the 26S proteasome antagonises the PcG by degrading the key PcG member EMBRYONIC FLOWER 1 (EMF1), which is likely to be important for implementing target gene repression. Surprisingly, my proteomic analysis showed that the novel trxG members ALP1 and ALP2 are accessory components of a core PcG complex – the Polycomb Repressive Complex 2 (PRC2) – in vivo, suggesting that that ALP1 and ALP2 may antagonise PcG repression by preventing the association of core PRC2 components with accessory components EMF1, LIKE HETEROCHROMATIN PROTEIN 1 and the PHD finger proteins VERNALISATION5 and VIN3-LIKE 1. My results reveal a previously unknown role for 26S proteasomal degradation in the regulation of PcG activity during vegetative development and identify novel in vivo associators of the core PRC2 and point to their role in modulating PcG activity. These results thereby increase our understanding of how the PcG is regulated and serve as a starting point to discover how specificity is given to the PcG mediated repression, either by targeted degradation of EMF1 by various E3 ligases or by different combinations of PRC2 associators.

Atherosclerosis is a slow-developing disease of large and medium sized arteries, and is the premier cardiovascular disease that underlies myocardial and cerebral infarction, aneurysm, stroke and gangrene of the extremities. At least 17 million people die of atherosclerotic complications each year worldwide, with another 15 million surviving unstable events. Despite therapeutic advances such as drug-eluting stents and statins, which reduce cardiovascular events by around 25%, there is an urgent need for additional strategies to complement these treatments and further reduce morbidity and mortality. Inflammation plays a fundamental role in mediating all stages of atherogenesis. The innate immune response has long been implicated in atherogenesis, and activation of the complement system has been associated with all stages of disease. In particular, C5b-9 (membrane attack complex) has been detected in human plaques and may be pathogenic. Since C5b-9 is produced in plaques then the complement activation product 5a (C5a) must also be generated. However, very little is known about the role of C5a in atherogenesis. Indeed, elevated levels of serum C5a have been detected in patients with advanced atherosclerosis and recently the classical C5a receptor, CD88, has been detected on most of the cells found in human atherosclerotic plaques. To date, no studies examining specific C5a receptor antagonism in an animal model of atherosclerosis have been performed. This thesis explored the potential therapeutic benefits of inhibiting C5a, using the C5a receptor antagonist, PMX53, in the ApoE knockout (ApoE-/-) mouse model of atherosclerosis. In Chapter 2, expression of both receptors to C5a, CD88 and C5L2, in aortae of ApoE -/- mice was explored. CD88 and C5L2 mRNA expression was detected in the aorta of ApoE -/- mice at 3, 5, 9,12, 17 and 25 weeks of age. CD88 expression in ApoE -/- mice increased with time, and with macrophage accumulation within the plaque, as indicated by an increase in expression of the macrophage marker, F4/80. Expresssion of CD88 was significantly increased at 17 and 26 weeks of age, compared with age-matched wild-type controls. C5L2 was also expressed albeit at much lower levels compared with wild-type controls. Having established the presence of C5a receptors in ApoE -/- mice, in Chapter 3, the effects PMX53-treatment on ApoE -/- mice on a normal chow diet was examined. PMX53 treatment (3 mg/kg; tri-weekly s.c., plus ~1mg/kg/day p.o. for 20 weeks) resulted in a significant reduction in neointimal area and therefore the intima:media ratio in the brachiocephalic artery compared to untreated controls (P < 0.05; n = 6-8). PMX53 treatment also reduced collagen content and outward remodelling of the brachiocephalic artery. In Chapter 4, studies exploring the effects of PMX53-treatment in the more inflammatory environment created by a high fat (or Western-type diet) were explored. Male ApoE -/- mice were treated with PMX53 from 5 – 25 weeks of age (3 mg/kg; tri-weekly s.c., plus v ~1mg/kg/day p.o.). Mice were placed on a high fat diet from 10 weeks of age. While PMX53- treated did not affect neo-intimal area, it did result in a significant increase in cell density (P<0.01; n=12) and a significant reduction in buried caps (P < 0.05; n = 12) in the brachiocephalic artery compared with untreated animals. Interestingly, PMX53-treated mice also had significantly reduced total cholesterol compared with untreated controls (P < 0.05; n = 12). These results provide the first evidence for a role for C5a in plaque destabilisation and cholesterol metabolism. Finally, Chapter 5 described the expression of CD88 and C5L2 in cultured primary rat vascular SMC was explored. Expression of CD88 and C5L2 was detected by Western blot; immunocytochemical analysis demonstrated intracellular expression of both C5L2 and CD88. Conversely, radioligand binding experiments suggested the presence of ~25000 cell surface receptors with a high affinity to C5a (KD = 0.3 nM). After establishing the presence of receptors to C5a, experiments were conducted to determine whether C5a has any functional effects on these cells. C5a induced a moderate increase in TNF-α release after 4 hours of treatment (P < 0.05, n = 3), but did not affect SMC proliferation (n = 3). In summary, this study is the first to demonstrate the benefits of specifically inhibiting C5a in a mouse model of atherosclerosis. These findings suggest that C5a plays a role in atherogenesis in ApoE -/- mice and that the C5a receptor antagonist PMX53 may have therapeutic potential in human atherosclerotic disease.

The G protein-coupled receptors (GPCRs) are important targets in drug discovery. In several cases, the endogenous ligands that activate the GPCRs of pharmaceutical interest are peptides. Unfortunately, peptides are in general not suitable as drugs, since the peptide structure is associated with several disadvantages, such as low oral bioavailability, rapid degradation and low receptor subtype selectivity. Thus, there is a strong need for drug-like nonpeptide ligands to peptide-activated GPCRs. However, to discover nonpeptide ligands that mimic the effect of the endogenous peptide, i.e. peptidomimetics, is a tremendous challenge. In fact, morphine and the related opioids were the only known examples of peptidomimetics before 1995 and these ligands were known long before the native endogenous peptide ligands were discovered. The main objective of the work described in this thesis was to design, synthesize and biologically evaluate selective nonpeptide agonists to the peptide-activated GPCR AT2. The AT2 receptor belongs to the renin–angiotensin system, where the octapeptide angiotensin II (Ang II) is the major effector peptide. Ang II mediates its effects through the two GPCRs AT1 and AT2. The AT1 receptor is already an established target in the treatment of hypertension. The physiological role of the AT2 receptor, which is up-regulated in certain pathological conditions, is not fully understood but it seems to include positive effects such as vasodilatation, tissue repair, tissue regeneration and neuronal differentiation. In the current investigation we started from the nonpeptide and nonselective (AT1/ AT2) compound L-162,313. This ligand is a known AT1 receptor agonist but its effect on the AT2 receptor was unknown at the start of this project. We were able to show that it acts as an agonist also at the AT2 receptor. Furthermore, stepwise synthetic modifications of L-162,313 led to the identification of the first selective nonpeptide AT2 receptor agonist. Following the discovery of this compound several selective nonpeptide AT2 receptor agonists were identified. It was also revealed that a minor structural alteration of one of these compounds interconverted the functional activity from agonism to antagonism. The structural requirement for agonism vs antagonism was therefore studied. The functionality switch was suggested, at least partly, to be due to the spatial relationship between the methyleneimidazole group and the isobutyl side chain of the compounds. To further investigate the bioactive conformation(s) of this series of compounds enantiomerically pure analogues with conformationally constrained isobutyl chains were prepared. This study revealed that the direction of the isobutyl side chain determine whether the compounds act as agonists or antagonists at the AT2 receptor. Further investigations are required to fully elucidate the bioactive conformation(s) of these nonpeptide AT2 receptor agonists. We believe that the selective nonpeptide AT2 receptor agonists and antagonists identified in this thesis will serve as important research tools in the continuing investigation of the physiological role of the AT2 receptor. We also believe that these drug-like compounds might provide potential leads in drug discovery processes.

Background: Intracellular glucocorticoid receptors (GRs) mediate the regulation of lung development, including alveolarization, by glucocorticoids (GCs). One potential approach to determining the role of GC-GR signalling in alveolar formation would be by pharmacologic blockade. Hypothesis: CP472555, a novel GR antagonist with negligible anti-PR activity, is a suitable tool for the study of GC-GR regulation of rat alveolarization. Design/Methods: CP472555 doses needed to block GR were estimated in vitro in fetal rat lung primary cultures. Postnatally, a variety of doses were administered intraperitoneally over a range of days. Results: During postnatal days (PN)0-PN10, when GC levels are low, CP472555 induced changes consistent with GR agonist activity. While GC levels increase after PN11, animals exposed to CP472555 from PN11-PN21 exhibit changes consistent with anti-GR antagonist activity. Conclusion: CP472555 causes a degree of GR blockade sufficient to permit further pharmacological investigation of the role of endogenous GC-GR signalling at the end of alveolarization.

Background: Intracellular glucocorticoid receptors (GRs) mediate the regulation of lung development, including alveolarization, by glucocorticoids (GCs). One potential approach to determining the role of GC-GR signalling in alveolar formation would be by pharmacologic blockade. Hypothesis: CP472555, a novel GR antagonist with negligible anti-PR activity, is a suitable tool for the study of GC-GR regulation of rat alveolarization. Design/Methods: CP472555 doses needed to block GR were estimated in vitro in fetal rat lung primary cultures. Postnatally, a variety of doses were administered intraperitoneally over a range of days. Results: During postnatal days (PN)0-PN10, when GC levels are low, CP472555 induced changes consistent with GR agonist activity. While GC levels increase after PN11, animals exposed to CP472555 from PN11-PN21 exhibit changes consistent with anti-GR antagonist activity. Conclusion: CP472555 causes a degree of GR blockade sufficient to permit further pharmacological investigation of the role of endogenous GC-GR signalling at the end of alveolarization.

Introducción: Desde su primera descripción en 1984 las indicaciones de donación de óvulos han ido aumentando, lo que ha provocado un incremento progresivo en el número de ciclos realizados a nivel mundial. Aunque esta técnica de reproducción garantiza una elevada tasa de embarazo en la receptora, los profesionales también se esfuerzan en convertir el tratamiento para la donante en un proceso sencillo y seguro. Durante los últimos diez años los antagonistas de la GnRH, por sus características farmacodinámicas, ha sido el fármaco utilizado para desarrollar protocolos de estimulaciones ováricas sencillos y seguros para las donantes de óvulos. Materiales: La presente tesis doctoral resume las conclusiones de dos artículos publicados recientemente (2010) sobre la utilización de antagonistas de GnRH en la estimulación ovárica de donantes de óvulos. Además se discuten las conclusiones de otros cuatro artículos (publicados en revistas científicas de impacto durante los años 2006 y 2009) estrechamente relacionados a los aquí publicados. Los objetivos de esta tesis son: 1. comparar la eficacia de protocolos de estimulación basados en antagonistas de GnRH en comparación con protocolos basados en agonistas de GnRH a través de una revisión sistemática de la literatura y meta-análisis. 2. ilustrar que los protocolos de estimulación basados en antagonistas de GnRH aumentan la seguridad de la estimulación ovárica para la donante a través de una eliminación completa del riesgo del síndrome de hiperestimulación ovárica (SHO). Resultados: 1. El meta-análisis de de ocho ensayos clínicos llevados al cabo en donantes de óvulos estimuladas con antagonistas de GnRH no han demostrado diferencia significativa en el número de ovocitos obtenidos y las tasas de embarazo evolutivos en las receptoras correspondientes en comparación con agonistas de GnRH. 2. El estudio observacional, prospectivo realizado en donantes de óvulos de alto riesgo ha demostrado la eliminación completa de SHO moderado/severo tras la descarga con bolo de agonista de GnRH. Además se discuten las conclusiones de cuatro otros estudios apoyando las conclusiones mencionados arriba. Conclusiones: En el contexto de la donación de óvulos los protocolos de estimulación ovárica basados en antagonistas de la GnRH son igual de eficaces que los protocolos con agonistas de la GnRH. La inducción final de la maduración ovocitaria se puede llevar a cabo satisfactoriamente con un bolo de agonista de GnRH en vez de hCG, lo que prácticamente elimina el riesgo de SHO moderado/severo. La utilización preferencial de este protocolo de estimulación ovárica es muy aconsejable porque permite un tratamiento más sencillo y aumenta considerablemente la seguridad de la estimulación ovárica en donantes de óvulos. / Background: Since its first description in 1984 the indications of oocyte donation (OD) has widened considerably which has led to a continuous increase in the number of OD treatment cycles performed worldwide. Although this treatment option secured the highest pregnancy rates for the recipients of donor oocytes increased efforts were also made to achieve safer and simpler treament protocols for the oocyte donor. During the last decade with the advent and increased use of the GnRH antagonists this new pharmacological agent was also explored in ovarian stimulation protocols specifically tailored for oocyte donors. Materials: The present doctoral thesis summarizes the findings of two recently published articles (2010) on the application of GnRH antagonists in the ovarian stimulation of oocyte donors. Furthermore the findings of another four strictly related articles (published in high-impact international journals between 2006 and 2009) are also discussed. The primary objectives were: 1. to compare efficiency of GnRH antagonist protocols in comparison with GnRH agonist-based protocols in the context of oocyte donation by means of a systematic review and meta-analysis and 2. to illustrate that GnRH antagonist protocols substantially increase the safety of ovarian stimulation for oocyte donors by reducing or even eliminating the incidence of moderate/severe ovarian hyperstimulation syndrome (OHSS). Results: 1. A meta-analysis of eight randomized clinical trials (RCTs) performed in oocyte donors undergoing stimulation with GnRH antagonists showed no significant difference in the number of retrieved oocytes or recipient ongoing pregnancy rate when compared with GnRH agonists. 2. A prospective, follow-up study of a group of high risk oocyte donors showed that early onset moderate/severe OHSS was completely eliminated after triggering with a GnRH agonist. Furthermore the findings of four studies supporting the above conclusions are also presented. Conclusions: In the context of oocyte donation the GnRH antagonist based ovarian stimulation protocols are equally efficient compared to down regulation by GnRH agonists. The induction of final oocyte maturation can be successfully achieved by a GnRH agonist instead of hCG which practically eliminates early-onset moderate/severe OHSS. The proposed ovarian stimulation protocol should be preferentially used because it permits the simplification and considerably increases the safety of ovarian stimulation for oocyte donors.

Previous studies show that coronary artery disease (CAD) is a multi-factors and chronic inflammatory disease, and is associated with lipid metabolism. IL-1ra is a naturally occurring anti-inflammatory molecules that block the action of IL-1. However, little is known about the imbalance between IL-1ra and inflammatory mediators in CAD. We attempted to investigate the relationships between inflammatory mediators and serum IL-1ra levels in patients with CAD. In 95 patients with angiographically defined CAD, and 70 healthy controls were studied in a case-control manner. Serum levels of cytokines and the risk factor of CAD were examined. Polymorphisms for IL-1ra gene were detected by PCR, and genotypes and allelic frequencies in both groups were compared. Our major finding include: (1) The risk factors such as elevated BMI, systolic BP, smoking, hypertension, blood glucose, and TG was more frequently found in the CAD group than the control group ( p < 0.001). However, the HDL-C and bilirubin were significantly higher in control group than the CAD group. (2) The relative risk of those in the highest quartile of ratio of LDL-C to HDL-C, TC to HDL-C, and TG to HDL-C were significantly elevated. ( OR = 2.98, p < 0.01; OR = 5.31, p <0.001; OR = 8.43, p < 0.001 respectively) (3) Five different inflammatory markers were significantly elevated including IL-1ra, hs-CRP, IL-6, leukocyte count, and neutrophil percentage between healthy controls and CAD patients. ( p < 0.01) (4) Levels of IL-1ra and other variables such as blood glucose, BMI, TG, IL-6, hs-CRP, and leukocyte count has significantly correlated, and were inversed correlation in bilirubin, and HDL-C in all study subjects. ( p < 0.01) (5) In the multiple logistic regression analysis, adjustment was made for variables. The relative risk of CAD for the highest quartile of IL-1ra, as compared with the lowest quartile, had an Odds ratio 2.57 ( 95% confidence intervals, 1.12 - 5.91, p = 0.026 ) increase in risk for CAD. (6) Similar results were obtained hs-CRP, IL-6 in the highest quartile were increase risk for future CAD. ( OR = 5.86 and 5.79 respectively; p < 0.001) (7) The join effect cytokines of hs-CRP, IL-6, IL-1ra concentrations may play important role in CAD risk. ( OR = 10.19, p < 0.001 ) (8) In addition, IL-1ra allele 2 genotype and allelic frequencies were no significant association with increase in IL-1ra with CAD. In conclusion, we find a significant association of elevated IL-1ra levels in the patients with CAD. Thus, these results support the hypothesis that inflammation, anti-inflammation cytokines and lipoprotein metabolism provide a useful marker for predicting the development of CAD events.

Rheumatoid arthritis is an autoimmune disease that can cause chronic inflammation of the joints and other areas of the body. Neutrophils contribute to the pathogenesis of arthritis, and are recruited to the site of inflammation by chemokines. CXCL8/IL-8 is a member of a sub-family of chemokines (ELR+CXC chemokines) that activate and attract neutrophils through the CXCR1 and CXCR2 receptors. Our lab developed a high affinity human CXCR1/CXCR2 antagonist, called human CXCL8(3-72)K11R/G31P (hG31P). This antagonist has been shown to be highly effective in blocking ELR+CXC chemokine-driven neutrophilic inflammation. In this study we looked at the therapeutic effect of blocking ELR+CXC chemokine receptors (CXCR1 and CXCR2) in an experimental model of arthritis. We induced type II collagen (CII)-induced arthritis (CIA) in mice and treated them with hG31P after the onset of disease. The parameters we looked at to assess disease severity were clinical scores (paws were graded on the severity of edema), clinical measurements (measuring inflammation by change in circumference of paw), serum levels of anti-CII antibodies, and inflammatory cytokines mRNA (IL-1β, TNF, KC, and MIP-2) and protein levels (IL-1β, IL-6, KC, and MIP-2) in paw tissue. Initially, when we analyzed all mice together, we were unable to see a change in clinical scores and measurement when CIA mice were treated with hG31P. All CIA mice did not develop arthritis simultaneously, but rather in a serendipitous fashion; therefore we subdivided our mice and analyzed data from mice that developed arthritis early versus those that developed it late. Treatment with hG31P in mice that developed arthritis early (within 5 weeks of initial CII injection) significantly reduced clinical scores (p=0.02) in one, but not both, of our experiments. When CIA mice were treated with hG31P we saw a significant reduction (p<0.05) in CII-specific IgG1 and MIP-2 protein levels in one of our experiments. Our results were variable and we did not see these changes in our other experiment. Treatment of CIA mice with G31P did not significantly affect inflammatory cytokine mRNA levels in the paws. During this study we found the production of anti-hG31P antibodies in our hG31P-treated mice. We used a Ca2+ influx assay to determine if these hG31P antibodies were neutralizing. When these antibodies were non-neutralizing we were able to see a significant reduction in the clinical scores (p=0.02) of our hG31P-treated CIA mice (that had developed early-onset arthritis) when compared to our saline-treated CIA mice. In the experiment in which we detected significant levels of neutralizing anti-hG31P antibodies, treatment with hG31P did not affect the clinical scores of our CIA mice. Although we cannot definitively say that hG31P has a therapeutic effect in CIA, we believe this line of research merits further investigation. Our research suggests to us that after some experimental refinement and reduction of the immune response mounted to hG31P, there could still be potential for hG31P to have a therapeutic effect in arthritis.

This thesis is focused on the development, preclinical evaluation, and optimization of radiotracers for the detection of gastrin-releasing peptide receptor (GRPR)-expressing tumors. The work is divided into three distinct parts: (1) the development of bombesin (BN) antagonist (RM26)-based imaging radiotracers for the detection of GRPR-expressing tumors using different positron emission tomography (PET) and single photon emission computed tomography (SPECT) radionuclides (68Ga, 18F and 111In), (2) the establishment of a method to monitor the ligand-G protein-coupled receptor (GPCR) interaction in real time without requiring purification and stabilization of the receptors, and (3) the evaluation of radiopeptide structure-related factors (length of mini-PEG linker and composition of chelator for metal labeling) affecting the in vitro and in vivo characteristics of RM26-based tracers. We demonstrated the possibility of high-contrast in vivo imaging of GRPR-expressing xenografts despite the physiological expression of GRPR in abdominal organs. Fast radioactivity clearance from the blood and healthy organs, including receptor-positive organs, and long retention in the tumors resulted in high tumor-to-background ratios. A novel real-time assay for measuring the kinetics of the radiotracers targeting GPCR was evaluated. Living cells were used instead of purified receptors in this technology, bringing the developmental work one step closer to the true target environment (imaging in living systems). The comparative study of 68Ga-labeled NOTA-PEGn-RM26 with di-, tri-, tetra- and hexaethylene glycol chains demonstrated that the addition of only a few units of ethylene glycol to the spacer is insufficient to appreciably affect the biodistribution of the radiopeptide. Finally, a comparative study of 68Ga-labeled PEG2-RM26 analogs N-terminally conjugated to NOTA, NODAGA, DOTA or DOTAGA highlighted the influence of the chelator on the targeting properties of the radiopeptide. The main conclusion that can be drawn from this thesis is that 68Ga-NOTA-PEG2-RM26 has favorable biodistribution properties, such as rapid clearance from blood and tissues with physiological GRPR expression levels and long retention in GRPR-expressing tumors, and that this radiopeptide is potentially suitable for initial clinical investigation.