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Purpose:[177Lu]Lu-PSMA-617 radioligand therapy (177Lu-PSMA) is a novel treatment for metastatic castration-resistant prostate cancer (mCRPC), which could also be applied to patients with metastatic hormone-sensitive prostate cancer (mHSPC) with PSMA expression. In this prospective study (NCT03828838), we analyzed toxicity, radiation doses, and treatment effect of 177Lu-PSMA in pateints with low-volume mHSPC.Patients and Methods:Ten progressive patients with mHSPC following local treatment, with a maximum of ten metastatic lesions on [68Ga]Ga-PSMA-11 PET/diagnostic-CT imaging (PSMA-PET) and serum PSA doubling time 177Lu-PSMA. Whole-body single-photon emission CT/CT (SPECT/CT) and blood dosimetry was performed to calculate doses to the tumors and organs at risk (OAR). Adverse events (AE), laboratory values (monitoring response and toxicity), and quality of life were monitored until week 24 after cycle 2, the end of study (EOS). All patients underwent PSMA-PET at screening, 8 weeks after cycle 1, 12 weeks after cycle 2, and at EOS.Results:All patients received two cycles of 177Lu-PSMA without complications. No treatment-related grade III–IV adverse events were observed. According to dosimetry, none of the OAR reached threshold doses for radiation-related toxicity. Moreover, all target lesions received a higher radiation dose than the OAR. All 10 patients showed altered PSA kinetics, postponed androgen deprivation therapy, and maintained good quality of life. Half of the patients showed a PSA response of more than 50%. One patient had a complete response on PSMA-PET imaging until EOS and two others had only minimal residual disease.Conclusions:177Lu-PSMA appeared to be a feasible and safe treatment modality in patients with low-volume mHSPC.

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Purpose: [177Lu]Lu-PSMA-617 radioligand therapy (177Lu-PSMA) is a novel treatment for metastatic castration-resistant prostate cancer (mCRPC), which could also be applied to patients with metastatic hormone-sensitive prostate cancer (mHSPC) with PSMA expression. In this prospective study (NCT03828838), we analyzed toxicity, radiation doses, and treatment effect of 177Lu-PSMA in pateints with low-volume mHSPC. Patients and Methods: Ten progressive patients with mHSPC following local treatment, with a maximum of ten metastatic lesions on [68Ga]Ga-PSMA-11 PET/diagnostic-CT imaging (PSMA-PET) and serum PSA doubling time Results: All patients received two cycles of 177Lu-PSMA without complications. No treatment-related grade III–IV adverse events were observed. According to dosimetry, none of the OAR reached threshold doses for radiation-related toxicity. Moreover, all target lesions received a higher radiation dose than the OAR. All 10 patients showed altered PSA kinetics, postponed androgen deprivation therapy, and maintained good quality of life. Half of the patients showed a PSA response of more than 50%. One patient had a complete response on PSMA-PET imaging until EOS and two others had only minimal residual disease. Conclusions: 177Lu-PSMA appeared to be a feasible and safe treatment modality in patients with low-volume mHSPC.

Surgery with curative intent can be offered to congenital hyperinsulinism (CHI) patients, provided that the lesion is focal. Radiolabeled exendin-4 specifically binds the glucagonlike peptide 1 receptor on pancreatic β-cells. In this study, we compared the performance of 18F-DOPA PET/CT, the current standard imaging method for CHI, and PET/CT with the new tracer 68Ga-NODAGA-exendin-4 in the preoperative detection of focal CHI. Methods: Nineteen CHI patients underwent both 18F-DOPA PET/CT and 68Ga-NODAGA-exendin-4 PET/CT before surgery. The images were evaluated in 3 settings: a standard clinical reading, a masked expert reading, and a joint reading. The target (lesion)-to-nontarget (normal pancreas) ratio was determined using SUVmax Image quality was rated by pediatric surgeons in a questionnaire. Results: Fourteen of 19 patients having focal lesions underwent surgery. On the basis of clinical readings, the sensitivity of 68Ga-NODAGA-exendin-4 PET/CT (100%; 95% CI, 77%-100%) was higher than that of 18F-DOPA PET/CT (71%; 95% CI, 42%-92%). Interobserver agreement between readings was higher for 68Ga-NODAGA-exendin-4 than for 18F-DOPA PET/CT (Fleiss κ = 0.91 vs. 0.56). 68Ga-NODAGA-exendin-4 PET/CT provided significantly (P = 0.021) higher target-to-nontarget ratios (2.02 ± 0.65) than did 18F-DOPA PET/CT (1.40 ± 0.40). On a 5-point scale, pediatric surgeons rated 68Ga-NODAGA-exendin-4 PET/CT as superior to 18F-DOPA PET/CT. Conclusion: For the detection of focal CHI, 68Ga-NODAGA-exendin-4 PET/CT has higher clinical sensitivity and better interobserver correlation than 18F-DOPA PET/CT. Better contrast and image quality make 68Ga-NODAGA-exendin-4 PET/CT superior to 18F-DOPA PET/CT in surgeons' intraoperative quest for lesion localization. ispartof: JOURNAL OF NUCLEAR MEDICINE vol:63 issue:2 pages:310-315 ispartof: location:United States status: published

Introduction While [177Lu]Lu-PSMA radioligand therapy is currently only applied in end-stage metastatic castrate-resistant prostate cancer (mCRPC) patients, also low-volume hormone-sensitive metastatic prostate cancer (mHSPC) patients can benefit from it. However, there are toxicity concerns related to the sink effect in low-volume disease. This prospective study aims to determine the kinetics of [177Lu]Lu-PSMA in mHSPC patients, analyzing the doses to organs at risk (salivary glands, kidneys, liver, and bone marrow) and tumor lesions Methods Ten mHSPC patients underwent two cycles of [177Lu]Lu-PSMA therapy. Three-bed position SPECT/CT was performed at 5 time points after each therapy. Organ dosimetry and lesion dosimetry were performed using commercial software and a manual approach, respectively. Correlation between absorbed index lesion dose and treatment response (PSA drop of > 50% at the end of the study) was calculated and given as Spearman’s r and p-values. Results Kinetics of [177Lu]Lu-PSMA in mHSPC patients are comparable to those in mCRPC patients. Lesion absorbed dose was high (3.25 ± 3.19 Gy/GBq) compared to organ absorbed dose (salivary glands: 0.39 ± 0.17 Gy/GBq, kidneys: 0.49 ± 0.11 Gy/GBq, liver: 0.09 ± 0.01 Gy/GBq, bone marrow: 0.017 ± 0.008 Gy/GBq). A statistically significant correlation was found between treatment response and absorbed index lesion dose (p = 0.047). Conclusions We successfully performed small lesion dosimetry and showed that the tumor sink effect in mHSPC patients is of less concern than was expected. Tumor-to-organ ratio of absorbed dose was high and tumor uptake correlates with PSA response. Additional treatment cycles are legitimate in terms of organ toxicity and could lead to better tumor response.

Currently, radionuclide imaging after injection of radiolabeled tracers seems to be the most promising approach to noninvasively determine the beta cell mass (BCM) in vivo. Despite the limited resolution of positron emission tomography (PET) and single photon emission computed tomography (SPECT), the very high sensitivity of these imaging modalities allows detection of very low radiotracer concentrations. Since the noninvasive imaging modalities that offer the highest spatial resolution, i.e., computed tomography (CT) and magnetic resonance imaging (MRI), which are not able to resolve single islets in vivo, radionuclide imaging would be the method of choice for beta cell imaging. However, noninvasive visualization of the pancreatic beta cells is a highly challenging endeavor. The beta cells are located in the islets of Langerhans in the pancreas. The islets are small (usually between 50 and 400 μm), only account for 1–2 % of the total pancreatic mass, and are spread throughout the pancreas (Bonner-Weir 1994; Weir et al. 1990). Targeting of these small structures spread through an organ is highly challenging when compared to tumor imaging, where a focal solid mass containing the target cells is visualized. Moreover, the islets consist of several cell types (beta cells, alpha cells, delta cells, and pp cells) with the beta cells representing around 60–80 % of the islet mass, making specific visualization of beta cells even more difficult. Since PET and SPECT cannot resolve single islets, let alone beta cells, a highly beta cell-specific radiotracer is required. Only when the radiotracer specifically accumulates in beta cells and not in other cell types of the endocrine or exocrine pancreas, the accumulation of the radiotracer in the pancreas could be used as a surrogate measure of the beta cell mass. To enable this, a target specifically expressed on beta cells and an optimal respective ligand should be selected for the development of beta cell targeting radiotracers. In contrast to tumor imaging, where several targets are overexpressed, beta cells express endogenous levels of receptors leading to generally lower accumulation of radiotracers when compared to tumor cells. In this book chapter, the challenges regarding tracer development and preclinical and clinical characterization will be discussed in detail.

Item does not contain fulltext Bone morphogenic protein-2 (BMP-2) is a well-known growth factor that can improve the biological performance of bone substitute materials. BMP-2 produced via bacterial expression systems are non-glycosylated (ng) whereas native and recombinant equivalents produced in mammalian cell expression systems are glycosylated (g) proteins. ngBMP-2 is less soluble, resulting in lower BMP-2 release from carriers as used as bone substitute materials. This seems promising for reducing the amount of included growth factor in bone substitute materials. Hence, it was hypothesized that ngBMP-2 would induce formation of the same amount of bone at an ectopic site at lower dosage as gBMP-2. To that end, gBMP-2 and ngBMP-2 were firstly in vitro comparatively evaluated for biological activity and release from a calcium phosphate (CaP) based bone substitute material. Thereafter, an ectopic implantation model in rats was used, in which gBMP-2 and ngBMP2 were loaded in various dosages (2-20 mug/implant) on the CaP-based bone substitute material and implanted for 4 and 12 weeks. The results revealed that both the in vitro biological activity of and the in vitro release of ngBMP-2 are lower compared to gBMP2. Upon ectopic implantation, however, ngBMP-2 loaded implants induced more bone formation at lower concentrations from 4-weeks onward compared to gBMP-2 equivalents, indicating the value of ngBMP-2 as a potential alternative for mammalian produced recombinant BMP-2 for bone regenerative therapies.

Contains fulltext : 103436.pdf (Publisher’s version ) (Open Access) Cholecystokinin (CCK) receptors are overexpressed in several human tumor types, such as medullary thyroid carcinomas and small cell lung cancers. Several ligands for the CCK2 receptor (CCK2R) have been developed for radionuclide targeting of these tumors. In this study, we evaluated whether radiolabeled DOTA-sCCK8 and its stabilized derivative, DOTA-sCCK8[Phe(2)(p-CH2SO3H), Nle(3,6)], are suitable for imaging of CCK2R-positive tumors, using DOTA-MG0 as a reference. In vivo targeting of CCK2R-positive tumors with DOTA-sCCK8, DOTA-sCCK8[Phe(2)(p-CH2SO3H), Nle(3,6)], and DOTA-MG0, labeled with (111)In or (68)Ga, was evaluated in BALB/c nude mice with a subcutaneous A431-CCK2R tumor. Biodistribution studies and single-photon emission computed tomography (SPECT) and positron emission tomography (PET) were performed at 1 hour postinjection. All peptides specifically accreted in the CCK2R-expressing tumors. Both (111)In-DOTA-sCCK8 and (111)In-DOTA-sCCK8[Phe(2)(p-CH2SO3H), Nle(3,6)] showed good tumor retention (4.65% ID/g and 5.44% ID/g, respectively, at 4 hours postinjection). On PET/computed tomographic (CT) and SPECT/CT scans, subcutaneous A431-CCK2R tumors were clearly visualized with low uptake of sCCK8 peptides in the intestines. Whereas radiolabeled DOTA-MG0 showed high kidney uptake (70% ID/g), the sCCK8 peptides showed low uptake in the kidneys. Sulfated CCK8 analogues combined high tumor uptake with low retention in the kidney and are therefore promising tracers for imaging of CCK2R-positive tumors.

Contains fulltext : 108912.pdf (Publisher’s version ) (Open Access) We recently reported a facile method based on the chelation of [(18)F]aluminum fluoride (Al(18)F) by NOTA (1,4,7-triazacyclononane-1,4,7-triacetic acid). Here, we present a further optimization of the (18)F labeling of NOTA-octreotide (IMP466). Octreotide was conjugated with the NOTA chelate and was labeled with (18)F in a two-step, one-pot method. The labeling procedure was optimized with regard to the labeling buffer, ionic strength, peptide concentration, and temperature. Radiochemical yield, specific activity, in vitro stability, and receptor affinity were determined. Biodistribution of (18)F-IMP466 was studied in AR42J tumor-bearing mice. In addition, microPET/CT images were acquired. IMP466 was labeled with Al(18)F in a single step with 97% yield in the presence of 80% (v/v) acetonitrile or ethanol. The labeled product was purified by HPLC to remove unlabeled peptide and unbound Al(18)F. The radiolabeling, including purification, was performed for 45 min. Specific activities of 48,000 GBq/mmol could be obtained. (18)F-IMP466 showed a high tumor uptake and excellent tumor-to-blood ratios at 2 h post-injection. In addition, the low bone uptake indicated that the Al(18)F-NOTA complex was stable in vivo. PET/CT scans revealed excellent tumor delineation and specific accumulation in the tumor. Uptake in receptor-negative organs was low. NOTA-octreotide could be labeled with (18)F in quantitative yields using a rapid two-step, one-pot, method. The compound was stable in vivo and showed rapid accretion in SSTR(2)-receptor-expressing AR42J tumors in nude mice. This method can be used to label other NOTA-conjugated compounds such as RGD peptides, GRPR-binding peptides, and Affibody molecules with (18)F. 01 april 2012

Contains fulltext : 98302.pdf (Publisher’s version ) (Closed access) PURPOSE: Radiolabelled peptides used for peptide receptor radionuclide therapy are excreted mainly via the kidneys and are partly reabsorbed and retained in the proximal tubular cells. The resulting high renal radiation dose can cause nephrotoxicity, limiting the maximum activity dose and the effectiveness of peptide receptor radionuclide therapy. The mechanisms of kidney reabsorption of these peptides are incompletely understood, but the scavenger receptor megalin has been shown to play a role in the reabsorption of (111)In-octreotide. In this study, the role of megalin in the renal reabsorption of various relevant radiolabelled peptides was investigated. METHODS: Groups of kidney-specific megalin-deficient mice and wild-type mice were injected with (111)In-labelled somatostatin, exendin, neurotensin or minigastrin analogues. Single photon emission computed tomographic (SPECT) images of the kidneys were acquired and analysed quantitatively, or the animals were killed 3 h after injection and the activity concentration in the kidneys was measured. RESULTS: Megalin-deficient mice showed significantly lower uptake of all studied radiolabelled peptides in the kidneys, ranging from 22% ((111)In-octreotide) to 65% ((111)In-exendin) of uptake in wild-type kidneys. Quantitative analysis of renal uptake by SPECT and ex vivo measurements showed a very good correlation. CONCLUSION: Megalin is involved in the renal reabsorption of radiolabelled octreotide, octreotate, exendin, neurotensin and minigastrin. This knowledge may help in the design of strategies to reduce this reabsorption and the resulting nephrotoxicity in peptide receptor radionuclide therapy, enabling more effective therapy. Small-animal SPECT is an accurate tool, allowing in vivo quantification of renal uptake and serial measurements in individual mice.

Contains fulltext : 89672.pdf (Publisher’s version ) (Closed access) Pretargeted radioimmunotherapy (PRIT) with bispecific antibodies in combination with a radiolabeled peptide reduces the radiation dose to normal tissues, especially the bone marrow. In this study, the optimization, therapeutic efficacy, and toxicity of PRIT of colon cancer with a (177)Lu-labeled peptide was determined in mice with carcinoembryonic antigen (CEA)-expressing human tumors. METHODS: To obtain the optimal therapeutic efficacy, several strategies were evaluated to increase the total amount of radioactivity targeted to subcutaneous LS174T colon cancer tumors in BALB/c nude mice. First, the maximum amount of bispecific anti-CEA and antihapten antibody TF2 and the peptide IMP288 that could be targeted was determined. Second, the tumor targeting of repeated administrations of radiolabeled IMP288 was investigated. Mice received 1 TF2 injection, followed by multiple IMP288 injections (3-h interval) or multiple cycles, with each IMP288 administration preceded by a new TF2 injection (72-h interval). PRIT was administered at maximum doses of TF2 and (177)Lu-labeled IMP288 in groups of 9 mice with subcutaneous LS174T tumors. Mice received 1, 2, or 3 successive cycles of treatment (26 MBq/mouse/cycle) or carrier only. The primary endpoint was survival; secondary endpoints were tumor growth, body weight, bone marrow, and renal toxicity. RESULTS: The highest amount of radioactivity delivered to a subcutaneous colon tumor was achieved by the administration of 5.0 nmol of TF2 and 0.28 nmol of IMP288 in 3 successive cycles, with each IMP288 preceded by a new TF2 injection (72-h interval). PRIT effectively delayed tumor growth and prolonged survival significantly. Higher activity doses, administered in successive cycles, correlated with longer survival: the median survival of untreated mice was 13 d (range, 6-20 d), whereas that of mice treated with 1, 2, or 3 cycles of PRIT was 24 (range, 24-31 d), 45 (range, 38 >/= 130 d), and 65 (range, 48 >/= 130 d) days, respectively. Toxicity was limited: no significant changes in mean body weight were measured. Minimal changes in leukocyte counts were measured at 2 and 3 wk after injection, with full recovery within 7 wk after treatment. Platelet counts were unaffected. Serum creatinine levels were not increased significantly; thus, there was no indication of acute renal toxicity. CONCLUSION: This study indicates that PRIT in mice is an effective treatment modality against colon cancer, with limited toxicity. 01 november 2010

Both radionuclide imaging and near-infrared fluorescent (NIRF) imaging have a high sensitivity to detect tumors in vivo. The combination of these modalities using dual-labeled antibodies may allow both preoperative and intraoperative tumor localization and may be used in image-guided surgery to ensure complete resection of tumor tissue. Here, we evaluated the potential of dual-modality imaging of prostate cancer with the monoclonal antibody D2B, directed against an extracellular domain of prostate-specific membrane antigen (PSMA). For these studies, D2B was labeled both with (111)In and with the NIRF dye IRDye800CW.METHODS: D2B was conjugated with N-hydroxysuccinimide-IRDye800CW and p-isothiocyanatobenzyl-diethylenetriaminepentaacetic acid (ITC-DTPA) and subsequently radiolabeled with (111)In. For biodistribution and NIRF imaging, (111)In-DTPA-D2B-IRDye800CW (2 μg, 0.55 MBq/mouse) was injected intravenously into BALB/c nude mice with subcutaneous PSMA-expressing LNCaP tumors (right flank) and PSMA-negative PC3 tumors (left flank). The biodistribution was determined at 1, 2, 3, and 7 d after injection. In addition, micro-SPECT/CT and NIRF imaging with (111)In-DTPA-D2B-IRDye800CW (3 μg, 8.5 MBq/mouse) was performed on mice with intraperitoneally growing LS174T-PSMA tumors.RESULTS: (111)In-DTPA-D2B-IRDye800CW specifically accumulated in subcutaneous PSMA-positive LNCaP tumors (45.8 ± 8.0 percentage injected dose per gram at 168 h after injection), whereas uptake in subcutaneous PSMA-negative PC3 tumors was significantly lower (6.6 ± 1.3 percentage injected dose per gram at 168 h after injection). Intraperitoneal LS174T-PSMA tumors could be visualized specifically with both micro-SPECT/CT and NIRF imaging at 2 d after injection, and the feasibility of image-guided resection of intraperitoneal tumors was demonstrated in this model.CONCLUSION: Dual-labeled (111)In-DTPA-D2B-IRDye800CW enables specific and sensitive detection of prostate cancer lesions in vivo with micro-SPECT/CT and NIRF imaging. In addition to preoperative micro-SPECT/CT imaging to detect tumors, NIRF imaging enables image-guided surgical resection. These preclinical findings warrant clinical studies with (111)In-DTPA-D2B-IRDye800CW to improve tumor detection and resection in prostate cancer patients.

Contains fulltext : 117898.pdf (Publisher’s version ) (Open Access) BACKGROUND: Hepcidin is a central regulator of iron metabolism. Serum hepcidin levels are increased in patients with renal insufficiency, which may contribute to anemia. Urine hepcidin was found to be increased in some patients after cardiac surgery, and these patients were less likely to develop acute kidney injury. It has been suggested that urine hepcidin may protect by attenuating heme-mediated injury, but processes involved in urine hepcidin excretion are unknown. METHODS: To assess the role of tubular reabsorption we compared fractional excretion (FE) of hepcidin-25 with FE of beta2-microglobulin (beta2m) in 30 patients with various degrees of tubular impairment due to chronic renal disease. To prove that hepcidin is reabsorbed by the tubules in a megalin-dependent manner, we measured urine hepcidin-1 in wild-type and kidney specific megalin-deficient mice. Lastly, we evaluated FE of hepcidin-25 and beta2m in 19 patients who underwent cardiopulmonary bypass surgery. Hepcidin was measured by a mass spectrometry assay (MS), whereas beta2m was measured by ELISA. RESULTS: In patients with chronic renal disease, FE of hepcidin-25 was strongly correlated with FE of beta2m (r = 0.93, P

Contains fulltext : 118633.pdf (Publisher’s version ) (Closed access) Affibody molecules (6-7 kDa) are a new class of small robust three-helical scaffold proteins. Radiolabeled subnanomolar anti-HER2 affibody ZHER2:342 was developed for imaging of HER2 expression in tumors, and a clinical study has demonstrated that the (111)In- and (68)Ga-labeled affibody molecules can efficiently detect HER2 expressing metastases in breast cancer patients. However, a significant renal accumulation of radioactivity after systemic injection of a radiolabeled anti-HER2 affibody conjugate is observed. The aim of this study was to investigate the mechanism of renal reabsorption of anti-HER2 affibody at the molecular level. Renal accumulation of radiolabeled anti-HER2 affibody molecules was studied in a murine model and in vitro using opossum-derived proximal tubule (OK) cells. It was found that kidney reabsorption of affibody molecule was not driven by megalin/cubilin. Amino acids in the target-binding side of affibody molecule were involved in binding to OK cells. On OK cells, two types of receptors for anti-HER2 affibody molecule were found: KD1=0.8 nM, Bmax1=71,500 and KD2=9.2 nM, Bmax2=367,000. The results of the present study indicate that affibody molecule and other scaffold-based targeting proteins with a relatively low kidney uptake can be selected using in vitro studies with tubular kidney cells. Altai, Mohamed Varasteh, Zohreh Andersson, Karl Eek, Annemarie Boerman, Otto Orlova, Anna Research Support, Non-U.S. Gov't United States Cancer Biother Radiopharm. 2013 Apr;28(3):187-95. doi: 10.1089/cbr.2012.1304. Epub 2013 Mar 5.

Cholecystokinin (CCK) receptors are overexpressed in several human tumor types, such as medullary thyroid carcinomas and small cell lung cancers. Several ligands for the CCK2 receptor (CCK2R) have been developed for radionuclide targeting of these tumors. In this study, we evaluated whether radiolabeled DOTA-sCCK8 and its stabilized derivative, DOTA-sCCK8[Phe(2)(p-CH2SO3H), Nle(3,6)], are suitable for imaging of CCK2R-positive tumors, using DOTA-MG0 as a reference. In vivo targeting of CCK2R-positive tumors with DOTA-sCCK8, DOTA-sCCK8[Phe(2)(p-CH2SO3H), Nle(3,6)], and DOTA-MG0, labeled with (111)In or (68)Ga, was evaluated in BALB/c nude mice with a subcutaneous A431-CCK2R tumor. Biodistribution studies and single-photon emission computed tomography (SPECT) and positron emission tomography (PET) were performed at 1 hour postinjection. All peptides specifically accreted in the CCK2R-expressing tumors. Both (111)In-DOTA-sCCK8 and (111)In-DOTA-sCCK8[Phe(2)(p-CH2SO3H), Nle(3,6)] showed good tumor retention (4.65% ID/g and 5.44% ID/g, respectively, at 4 hours postinjection). On PET/computed tomographic (CT) and SPECT/CT scans, subcutaneous A431-CCK2R tumors were clearly visualized with low uptake of sCCK8 peptides in the intestines. Whereas radiolabeled DOTA-MG0 showed high kidney uptake (70% ID/g), the sCCK8 peptides showed low uptake in the kidneys. Sulfated CCK8 analogues combined high tumor uptake with low retention in the kidney and are therefore promising tracers for imaging of CCK2R-positive tumors.

Contains fulltext : 96614.pdf (Publisher’s version ) (Closed access) OBJECTIVE: The aim of this study was to test the hypothesis that adjuvant radioimmunotherapy (RIT) prevents recurrent liver metastases and/or results in improved survival after tumorectomy in an experimental model. BACKGROUND: Although partial hepatectomy can improve 5-year survival of patients with colorectal liver metastases up to 58%, recurrent tumor growth in the liver occurs frequently. Radioimmunotherapy using radiolabeled monoclonal antibodies directed against tumor-associated antigens is considered most suited for treating minimal residual disease and could therefore serve as an adjuvant after surgery. METHODS: Liver metastases were induced in male Wag/Rij rats by a mini-laparotomy with intrahepatic injection of 0.3 x 106 CC531 tumor cells. The biodistribution of the radiolabeled monoclonal antibody MG1, directed against a 80-kDa cell surface antigen on CC531 tumors, in this model was determined at 1, 3, and 7 days after intravenous administration. The therapeutic efficacy of 177Lu-MG1 was compared with that of a sham antibody (UPC10), labeled with the same activity dose of Lu-177, and saline only. Radioimmunotherapy was administered either at the day of the tumorectomy (day 14 after tumor cell inoculation) or 7 days later. Primary endpoint was survival. RESULTS: Radiolabeled MG1 preferentially accumulated in tumor lesions in the liver reaching a maximum 3 days postinjection (8.7 +/- 0.6% injected dose per gram). Both the administration of 177Lu-MG1 and 177Lu-UPC10 resulted in a transient decrease in body weight. No other signs of clinical discomfort were registered. The survival curves of the group that received 177Lu-UPC10 and the group that received saline only did not differ (P=0.886). Administration of RIT immediately after surgery improved survival compared to administration of the control antibody (hazard ratio [HR], 1.54; P = 0.051), which was even more pronounced when survival was adjusted for the weight of the resected tumor (HR, 1.71; P = 0.027). A therapeutic efficacy of delayed treatment seemed likely (HR, 2.34; P = 0.055). Survival after early administration did not differ from delayed administration (HR, 1.16; P = 0.763). CONCLUSION: This study provides proof of principle that RIT can be an effective adjuvant treatment modality after surgical treatment of colorectal liver metastases.

Contains fulltext : 97745.pdf (Publisher’s version ) (Closed access) PURPOSE: Cholecystokinin 2 (CCK-2) receptor overexpression has been demonstrated in various tumours such as medullary thyroid carcinomas and small-cell lung cancers. Due to this high expression, CCK-2 receptors might be suitable targets for radionuclide imaging and/or radionuclide therapy. Several CCK-2 receptor-binding radiopeptides have been developed and some have been tested in patients. Here we aimed to compare the in vivo tumour targeting properties of 12 (111)In-labelled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated gastrin/CCK2 receptor-binding peptides. METHODS: Two CCK8-based peptides and ten gastrin-based peptide analogues were tested. All peptides were conjugated with DOTA and labelled with (111)In. Biodistribution studies were performed in mice with subcutaneous CCK2/gastrin receptor-expressing tumours and with receptor-negative tumours contralaterally. Biodistribution was studied by counting dissected tissues at 1 and 4 h after injection. RESULTS: Both the CCK analogues displayed relatively low tumour uptake (approximately 2.5%ID/g) as compared to minigastrin analogues. Two linear minigastrin peptides (MG0 and sargastrin) displayed moderate tumour uptake at both 1 and 4 h after injection, but also very high kidney uptake (both higher than 48%ID/g). The linear MG11, lacking the penta-Glu sequence, showed lower tumour uptake and also low kidney uptake. Varying the N-terminal Glu residues in the minigastrin analogues led to improved tumour targeting properties, with PP-F11 displaying the optimal biodistribution. Besides the monomeric linear peptides, a cyclized peptide and a divalent peptide were tested. CONCLUSION: Based on these studies, optimal peptides for peptide receptor radionuclide targeting of CCK2/gastrin receptor-expressing tumours were the linear minigastrin analogue with six D-Glu residues (PP-F11), the divalent analogue MGD5 and the cyclic peptide cyclo-MG1. These peptides combined high tumour uptake with low kidney retention, and may therefore be good candidates for future clinical studies.

Purpose Cholecystokinin 2 (CCK-2) receptor overexpression has been demonstrated in various tumours such as medullary thyroid carcinomas and small-cell lung cancers. Due to this high expression, CCK-2 receptors might be suitable targets for radionuclide imaging and/or radionuclide therapy. Several CCK-2 receptor-binding radiopeptides have been developed and some have been tested in patients. Here we aimed to compare the in vivo tumour targeting properties of 12 111In-labelled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated gastrin/CCK2 receptor-binding peptides. Methods Two CCK8-based peptides and ten gastrin-based peptide analogues were tested. All peptides were conjugated with DOTA and labelled with 111In. Biodistribution studies were performed in mice with subcutaneous CCK2/gastrin receptor-expressing tumours and with receptor-negative tumours contralaterally. Biodistribution was studied by counting dissected tissues at 1 and 4 h after injection. Results Both the CCK analogues displayed relatively low tumour uptake (approximately 2.5%ID/g) as compared to minigastrin analogues. Two linear minigastrin peptides (MG0 and sargastrin) displayed moderate tumour uptake at both 1 and 4 h after injection, but also very high kidney uptake (both higher than 48%ID/g). The linear MG11, lacking the penta-Glu sequence, showed lower tumour uptake and also low kidney uptake. Varying the N-terminal Glu residues in the minigastrin analogues led to improved tumour targeting properties, with PP-F11 displaying the optimal biodistribution. Besides the monomeric linear peptides, a cyclized peptide and a divalent peptide were tested. Conclusion Based on these studies, optimal peptides for peptide receptor radionuclide targeting of CCK2/gastrin receptor-expressing tumours were the linear minigastrin analogue with six D-Glu residues (PP-F11), the divalent analogue MGD5 and the cyclic peptide cyclo-MG1. These peptides combined high tumour uptake with low kidney retention, and may therefore be good candidates for future clinical studies.

Item does not contain fulltext We report on the SSTR2-binding properties of a series of four dimeric [Tyr3]octreotate analogues with different spacer lengths (nine, 19, 41, and 57 atoms) between the peptides. Two analogues (9 and 57 atoms) were selected as precursors for the design, synthesis, and biological evaluation of DOTA-conjugated dimeric [Tyr3]octreotate analogues for tumor targeting. These compounds were synthesized by using a two-stage click ligation procedure: a Cu(I) -catalyzed 1,3-dipolar cycloaddition ("copper-click" reaction) and a thio acid/sulfonyl azide amidation ("sulfo-click" reaction). The IC(50) values of these DOTA-conjugated [Tyr3]octreotate analogues were comparable, and internalization studies showed that the nine-atom (111) In-DOTA-labeled [Tyr3]octreotate dimer had rapid and high receptor binding. Biodistribution studies with BALB/c nude mice bearing subcutaneous AR42J tumors showed that the (111) In-labeled [Tyr3]octreotate dimer (nine atoms) had a high tumor uptake at 1 h p.i. (38.8 +/- 8.3 % ID g(-1) ), and excellent tumor retention at 4 h p.i. (40.9 +/- 2.5 % ID g(-1) ). However, the introduction of the extended hydrophilic 57 atoms spacer led to rapid clearance from the circulation; this limited tumor accumulation of the radiotracer (21.4 +/- 4.9 % ID g(-1) at 1 h p.i.). These findings provide important insight on dimerization and spacer effects on the in vivo properties of DOTA-conjugated [Tyr3]octreotate dimers.

Background Radioimmunotherapy (RIT) has been shown to reduce the incidence of local recurrence of colorectal cancer in an experimental model. The aim of the present study was to investigate the survival benefit of RIT compared with chemotherapy. Methods An anastomosis was constructed in male Wag/Rij rats after intraluminal injection of CC531 tumour cells. The therapeutic efficacy of 177Lu-labelled MG1 (single intravenous dose of 300 MBq/kg, n = 20) was compared with that of 5-fluorouracil-based chemotherapy (6 weekly cycles administered intraperitoneally, n = 20) and no treatment (n = 20). The primary endpoint was survival. Toxicity was monitored by bodyweight measurement. Results Both chemotherapy and RIT affected bodyweight, but the weight of animals in the RIT group remained significantly higher than in the chemotherapy group (median slope of bodyweight plot 0·48 versus 0·30 g/day; P < 0·001). Kaplan–Meier analysis showed that overall survival in the RIT and chemotherapy groups was significantly better than that in the control group (50 and 46 per cent versus 25 per cent respectively after 170 days; P = 0·024 and P = 0·029). Survival after treatment with RIT did not differ from that after chemotherapy (P = 0·911). Conclusion RIT is as effective as chemotherapy in experimental colorectal cancer.

Contains fulltext : 87734.pdf (Publisher’s version ) (Closed access) Several methods have been developed to label peptides with (18)F. However, in general these are laborious and require a multistep synthesis. We present a facile method based on the chelation of (18)F-aluminum fluoride (Al(18)F) by 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA). The method is characterized by the labeling of NOTA-octreotide (NOTA-d-Phe-cyclo[Cys-Phe-d-Trp-Lys-Thr-Cys]-Throl (MH(+) 1305) [IMP466]) with (18)F. METHODS: Octreotide was conjugated with the NOTA chelate and labeled with (18)F in a 2-step, 1-pot method. The labeling procedure was optimized with regard to the labeling buffer, peptide, and aluminum concentration. Radiochemical yield, specific activity, in vitro stability, and receptor affinity were determined. Biodistribution of (18)F-IMP466 was studied in AR42J tumor-bearing mice and compared with that of (68)Ga-labeled IMP466. In addition, small-animal PET/CT images were acquired. RESULTS: IMP466 was labeled with Al(18)F in a single step with 50% yield. The labeled product was purified by high-performance liquid chromatography to remove unbound Al(18)F and unlabeled peptide. The radiolabeling, including purification, was performed in 45 min. The specific activity was 45,000 GBq/mmol, and the peptide was stable in serum for 4 h at 37 degrees C. Labeling was performed at pH 4.1 in sodium citrate, sodium acetate, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, and 2-(N-morpholino)ethanesulfonic acid buffer and was optimal in sodium acetate buffer. The apparent 50% inhibitory concentration of the (19)F-labeled IMP466 determined on AR42J cells was 3.6 nM. Biodistribution studies at 2 h after injection showed a high tumor uptake of (18)F-IMP466 (28.3 +/- 5.2 percentage injected dose per gram [%ID/g]; tumor-to-blood ratio, 300 +/- 90), which could be blocked by an excess of unlabeled peptide (8.6 +/- 0.7 %ID/g), indicating that the accumulation in the tumor was receptor-mediated. Biodistribution of (68)Ga-IMP466 was similar to that of (18)F-IMP466. (18)F-IMP466 was stable in vivo, because bone uptake was only 0.4 +/- 0.2 %ID/g, whereas free Al(18)F accumulated rapidly in the bone (36.9 +/- 5.0 %ID/g at 2 h after injection). Small-animal PET/CT scans showed excellent tumor delineation and high preferential accumulation in the tumor. CONCLUSION: NOTA-octreotide could be labeled rapidly and efficiently with (18)F using a 2-step, 1-pot method. The compound was stable in vivo and showed rapid accretion in somatostatin receptor subtype 2-expressing AR42J tumors in nude mice. This method can be used to label other NOTA-conjugated compounds with (18)F. 01 maart 2010

Contains fulltext : 83994.pdf (Publisher’s version ) (Open Access) Radiolabeled cholecystokinin-8 (CCK8) peptide analogues can be used for peptide receptor radionuclide imaging and therapy for tumors expressing CCK2/gastrin receptors. Earlier findings indicated that sulfated CCK8 (sCCK8, Asp-Tyr(OSO(3)H)-Met-Gly-Trp-Met-Asp-Phe-NH(2)) may have better characteristics for peptide receptor radionuclide therapy (PRRT) than gastrin analogues. However, sCCK8 contains an easily hydrolyzable sulfated tyrosine residue and two methionine residues which are prone to oxidation. Here, we describe the synthesis of stabilized sCCK8 analogues, resistant to hydrolysis and oxidation. Hydrolytic stability was achieved by replacement of the Tyr(OSO(3)H) moiety by a robust isosteric sulfonate, Phe(p-CH(2)SO(3)H). Replacement of methionine by norleucine (Nle) or homopropargylglycine (HPG) avoided undesired oxidation side-reactions. The phenylalanine analogue Phe(p-CH(2)SO(3)H) of l-tyrosine, synthesized by a modification of known synthetic routes, was incorporated in three peptides: sCCK8[Phe(2)(p-CH(2)SO(3)H),Met(3,6)], sCCK8[Phe(2)(p-CH(2)SO(3)H),Nle(3,6)], and sCCK8[Phe(2)(p-CH(2)SO(3)H),HPG(3,6)]. All peptides were N-terminally conjugated with the macrocyclic chelator DOTA (1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid) and radiolabeled with In-111. In vitro binding assays on CCK2R-expressing HEK293 cells revealed that all three peptides showed specific binding and receptor-mediated internalization, with binding affinity values (IC(50)) in the nanomolar range. In vitro oxidation studies demonstrated that peptides with Nle or HPG indeed were resistant to oxidation. In vivo targeting studies in mice with AR42J tumors showed that tumor uptake was highest for (111)In-DOTA-sCCK8 and (111)In-DOTA-sCCK8[Phe(2)(p-CH(2)SO(3)H),Nle(3,6)] (4.78 +/- 0.64 and 4.54 +/- 1.15%ID/g, respectively, 2 h p.i.). The peptide with the methionine residues replaced by norleucine ((111)In-DOTA-sCCK8[Phe(2)(p-CH(2)SO(3)H), Nle(3,6)]) showed promising in vivo characteristics and will be further investigated for radionuclide imaging and therapy of CCK2R-expressing tumors. 8 p.

Contains fulltext : 88022.pdf (Publisher’s version ) (Closed access) PURPOSE: In peptide-receptor radionuclide therapy (PRRT), the maximum activity dose that can safely be administered is limited by high renal uptake and retention of radiolabelled peptides. The kidney radiation dose can be reduced by coinfusion of agents that competitively inhibit the reabsorption of radiolabelled peptides, such as positively charged amino acids, Gelofusine, or trypsinised albumin. The aim of this study was to identify more specific and potent inhibitors of the kidney reabsorption of radiolabelled peptides, based on albumin. METHODS: Albumin was fragmented using cyanogen bromide and six albumin-derived peptides with different numbers of electric charges were selected and synthesised. The effect of albumin fragments (FRALB-C) and selected albumin-derived peptides on the internalisation of (111)In-albumin, (111)In-minigastrin, (111)In-exendin and (111)In-octreotide by megalin-expressing cells was assessed. In rats, the effect of Gelofusine and albumin-derived peptides on the renal uptake and biodistribution of (111)In-minigastrin, (111)In-exendin and (111)In-octreotide was determined. RESULTS: FRALB-C significantly reduced the uptake of all radiolabelled peptides in vitro. The albumin-derived peptides showed different potencies in reducing the uptake of (111)In-albumin, (111)In-exendin and (111)In-minigastrin in vitro. The most efficient albumin-derived peptide (peptide #6), was selected for in vivo testing. In rats, 5 mg of peptide #6 very efficiently inhibited the renal uptake of (111)In-minigastrin, by 88%. Uptake of (111)In-exendin and (111)In-octreotide was reduced by 26 and 33%, respectively. CONCLUSIONS: The albumin-derived peptide #6 efficiently inhibited the renal reabsorption of (111)In-minigastrin, (111)In-exendin and (111)In-octreotide and is a promising candidate for kidney protection in PRRT. 01 februari 2010

Contains fulltext : 89629.pdf (Publisher’s version ) (Closed access) (18)F-Fluorodeoxyglucose ((18)F-FDG) is the most common molecular imaging agent in oncology, with a high sensitivity and specificity for detecting several cancers. Antibodies could enhance specificity; therefore, procedures were developed for radiolabeling a small ( approximately 1451 Da) hapten peptide with (68)Ga or (18)F to compare their specificity with (18)F-FDG for detecting tumors using a pretargeting procedure. Mice were implanted with carcinoembryonic antigen (CEA; CEACAM5)-expressing LS174T human colonic tumors and a CEA-negative tumor, or an inflammation was induced in thigh muscle. A bispecific monoclonal anti-CEA x anti-hapten antibody was given to mice, and 16 hours later, 5 MBq of (68)Ga- or (18)F-labeled hapten peptides were administered intravenously. Within 1 hour, tissues showed high and specific targeting of (68)Ga-IMP-288, with 10.7 +/- 3.6% ID/g uptake in the tumor and very low uptake in normal tissues (e.g., tumor-to-blood ratio of 69.9 +/- 32.3), in a CEA-negative tumor (0.35 +/- 0.35% ID/g), and inflamed muscle (0.72 +/- 0.20% ID/g). (18)F-FDG localized efficiently in the tumor (7.42 +/- 0.20% ID/g) but also in the inflamed muscle (4.07 +/- 1.13% ID/g) and in several normal tissues; thus, pretargeted (68)Ga-IMP-288 provided better specificity and sensitivity. Positron emission tomography (PET)/computed tomography images reinforced the improved specificity of the pretargeting method. (18)F-labeled IMP-449 distributed similarly in the tumor and normal tissues as the (68)Ga-labeled IMP-288, indicating that either radiolabeled hapten peptide could be used. Thus, pretargeted immuno-PET does exceptionally well with short-lived radionuclides and is a highly sensitive procedure that is more specific than (18)F-FDG-PET. Mol Cancer Ther; 9(4); 1019-27. (c)2010 AACR. 01 april 2010

Contains fulltext : 80371.pdf (Publisher’s version ) (Open Access) In radioimmunotherapy (RIT), hematologic toxicity is the dose-limiting toxicity due to the long circulatory half-life of the antibody. Although intraperitoneal (i.p.) RIT results in high uptake of i.p. growing tumors, the radiolabeled antibody enters the circulation, resulting in bone marrow toxicity. Carbohydrate modification of antibodies could induce accelerated clearance of the antibody via the hepatic asialoglycoprotein receptor, thereby reducing exposure to normal tissues. In this study, we investigated whether galactosylation of an antibody in a model of peritoneal carcinomatosis (PC) of colonic origin could be used to improve targeting of i.p. growing tumors. Therefore, the biodistribution of the galactosylated and nongalactosylated anti-CC531 antibody, MG1, after i.p. injection was determined in a model of peritoneal carcinomatosis of CC-531 colon tumors in Wag/Rij rats. Uptake of the radiolabeled antibodies in the tumor and relevant organs was determined at 2, 4, 24, and 48 hours after injection. Galactosylation of the antibody did not affect the binding affinity of MG1. Remarkably, the uptake of Gal-MG1 in tumors was higher than that of MG1 at 2 and 4 hours after injection. After 24 and 48 hours, uptake of Gal-MG1 in tumor tissue was lower than that of MG1. Gal-MG1 cleared from the blood within hours after administration. At 2-24 hours after administration, tumor-to-blood ratios obtained with Gal-MG1 were significantly higher than those obtained with unmodified MG1. Antibody galactosylation resulted in improved tumor-non-tumor ratios after i.p. injection in a model of PC. This could improve the efficiency of RIT, especially in combination with short-lived nonresidualizing radionuclides.

Contains fulltext : 71199.pdf (Publisher’s version ) (Closed access) In most types of peptide receptor radionuclide therapy, the maximum activity dose that can be administered is limited by high and persistent renal retention of the radiolabeled peptides, which is, at least partly, mediated by the megalin receptor. Several agents that interfere with renal reabsorption of radiolabeled peptides have been identified (e.g., lysine, arginine, succinylated gelatin solution), but none of these inhibit renal reabsorption completely. Albumin, a naturally abundant megalin ligand, might be a safe and potent alternative. In this study, we analyzed the effects of albumin and fragments of albumin (FRALB) on the renal reabsorption of (111)In-diethylenetriaminepentaacetic acid (DTPA)-d-Phe(1)-octreotide ((111)In-octreotide), [Lys(40)(aminohexoic acid-DTPA-(111)In)NH(2)]-exendin-4 ((111)In-exendin), and (111)In-1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-Glu(1)-minigastrin ((111)In-minigastrin). METHODS: The effects of albumin and FRALB on megalin-associated binding of (111)In-octreotide, (111)In-exendin, and (111)In-minigastrin were assessed in vitro using rat yolk sac epithelial (BN16) cells. In vivo, uptake and localization of (111)In-albumin and (111)In-FRALB in the kidneys of Wistar rats were determined, as well as the effect of lysine, succinylated gelatin solution, albumin, and FRALB on the kidney uptake of (111)In-octreotide, (111)In-exendin, and (111)In-minigastrin. RESULTS: FRALB significantly reduced binding and uptake of (111)In-octreotide, (111)In-exendin, and (111)In-minigastrin by BN16 cells. In rats, renal uptake of (111)In-labeled FRALB was significantly higher than that of (111)In-labeled intact albumin (P

Contains fulltext : 81771.pdf (Publisher’s version ) (Closed access) BACKGROUND: Half of the patients with colorectal cancer develop liver metastases during the course of their disease. The aim of the present study was to assess the efficacy of radioimmunotherapy (RIT) with a radiolabeled monoclonal antibody (mAb) to treat experimental colorectal liver metastases. METHODS: Male Wag/Rij rats underwent a minilaparotomy with intraportal injection of 1 x 10(6) CC531 tumor cells. The biodistribution of (111)In-labeled MG1, 1 day after intravenous administration, was determined in vivo and compared with that of an isotype-matched control antibody (UPC-10). The maximal tolerated dose (MTD) of (177)Lu-labeled MG1 was determined and the therapeutic efficacy of (177)Lu-MG1 at MTD was compared with that of (177)Lu-UPC-10 and saline only. RIT was administered either at the day of tumor inoculation or 14 days after tumor inoculation. Primary endpoint was survival. RESULTS: (111)In-MG1 preferentially accumulated in CC531 liver tumors (9.2 +/- 3.7%ID/g), whereas (111)In-UPC-10 did not (0.8 +/- 0.1%ID/g). The MTD of (177)Lu-MG1 was 400 MBq/kg body weight. Both the administration of (177)Lu-MG1 and (177)Lu-UPC-10 had no side-effects except a transient decrease in body weight. The survival curves of the group that received (177)Lu-UPC-10 and the group that received saline only did not differ (P = 0.407). Administration of (177)Lu-MG1 RIT immediately after surgery improved survival significantly compared with administration of (177)Lu-UPC-10 (P = 0.009) whereas delayed treatment did not (P = 0.940). CONCLUSION: This study provides proof of principle that RIT can be an effective treatment modality for microscopic liver metastases, whereas RIT is not effective in larger tumors.

Contains fulltext : 71090.pdf (Publisher’s version ) (Closed access) Induction of CTL responses by dendritic cell (DC)-based vaccines requires efficient DC-loading strategies for class I Ags. Coupling Ags to cell-penetrating peptides (CPPs) or receptor-specific Abs improves Ag loading of DCs. In contrast to CPPs, receptor-specific Abs deliver conjugated Ags to DCs with high specificity, which is advantageous for in vivo strategies. It has, however, been speculated that CPPs facilitate uptake and endosomal escape of conjugated Ags, which would potently enhance cross-presentation. In this study, we directly compare the in vitro targeting efficiency of a humanized D1 Ab directed against the human DC surface receptor DC-SIGN hD1 to that of three CPPs. The three CPPs colocalized within endosomes when targeted to human monocyte-derived DCs simultaneously, whereas hD1 was present in a different set of endosomes. However, within 75 min after uptake CPPs and hD1 colocalized extensively within the lysosomal compartment. Ab-mediated targeting of class I-restricted peptides to DC-SIGN enhanced cross-presentation of the peptides, while only one of the CPPs enhanced peptide presentation. This CPP and hD1 enhanced cross-presentation with equal efficiencies. Thus, we found no evidence of CPP specifically favoring the delivery of conjugated Ag to the DC class I presentation pathway. Given the specificity with which Abs recognize their targets, this favors the use of DC receptor-specific Abs for in vivo vaccination strategies.