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Background: Recently, radiotheranostics comprising the true matched radionuclide pair 203/212 Pb could serve as real dosimetric planning utility using 203 Pb-radiolabelled pharmaceuticals before therapy with 212 Pb-radiolabelled counterparts. 212 Pb might act as the missing radionuclide therapy between standard β - therapies (e.g. with 177 Lu or 90 Y), in some cases leading to β - resistance and highly cytotoxic α therapies (e.g. with 225 Ac) leading in some cases to renal insufficiency or even renal failure, due to the daughter nuclide 213 Bi, which accumulates in > 90% within the kidneys during 225 Ac therapy. 212 Pb converts to 212 Bi by β - -decay and the following pathway of decay bears in sum only one α decay, which certainly happens within the targeted tumour tissue. Following daughter nuclides (e.g. 208 Tl), which could distribute in organs at risk have only β - or γ decay, which is not as cytotoxic as α decay., Results: By ingenious customization of the standard cassettes of the ML EAZY it was possible to adapt the manual radiosynthesis of [ 212 Pb]Pb-PSC-PEG 2 -TOC ([ 212 Pb]Pb-VMT-α-NET) to a GMP-compliant synthesis module. The whole process of production, namely conditioning of C18 cartridge for purification, elution of the 224 Ra/ 212 Pb-generator, radiolabelling, C18 purification and sterile filtration performed automatically within one hour to access [ 212 Pb]Pb-VMT-α-NET for patient application. [ 212 Pb]Pb-VMT-α-NET was radiolabelled with high radiochemical purity > 95% and high radiochemical yield > 95% with molar activity ~ 15.8 MBq/nmol., Conclusions: The Lead-it-EAZY process performed stable and robust over ten radiosyntheses and yielded sterile [ 212 Pb]Pb-VMT-α-NET in high purity for patient application. By changing the precursor this process could easily be adapted to other 212 Pb-radiopharmaceuticals., Competing Interests: Declarations. Ethics approval and consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: The MiniScanPRO + was provided by Eckert&Ziegler especially for evaluation of α-particles on TLC. F.K. is employed by Eckert&Ziegler, which has financial interest in the Lead-it-EAZY cassette. M.K.S. and E.A.S. are employed by Perspective Therapeutics, which has financial interest in the VMT-α-NET radiopharmaceutical. The authors declare no further conflict of interest., (© 2024. The Author(s).)

Abstract: 212 Pb emerges as a compelling in vivo α-particle generator for targeted α therapy due to its favorable half-life ( t1/2 = 10.6 hours) aligning with the biological half-lives of small peptides and its potent α-particle emissions within the decay series. However, one of the challenges with 212 Pb is to perform appropriate image-guided dosimetry. To date, all the data have been extrapolated from its imaging analog, 203 Pb. We present the first-in-human posttherapy image-guided dosimetric estimates of a single cycle of 212 Pb VMT-α-peptide, administered in a 41-year-old woman with an advanced grade 2 NET. The patient also demonstrated partial response on treatment., Competing Interests: Conflicts of interest and sources of funding: M.K.S. is inventor of the peptide VMT-α-NET and chief science officer of Prospective Therapeutics. There is no conflict of interest with respect to the other authors. The 224 Ra/ 212 Pb generator and the VMT-α-NET peptide were provided by Perspective Therapeutics. The investigators have not received any fee or financial indemnity from Perspective Therapeutics., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.)

Purpose: Cancer treatment with alpha-emitter-based radioligand therapies (α-RLTs) demonstrates promising tumor responses. Radiolabeled peptides are filtered through glomeruli, followed by potential reabsorption of a fraction by proximal tubules, which may cause acute kidney injury (AKI) and chronic kidney disease (CKD). Because tubular cells are considered the primary site of radiopeptides' renal reabsorption and potential injury, the current use of kidney biomarkers of glomerular functional loss limits the evaluation of possible nephrotoxicity and its early detection. This study aimed to investigate whether urinary secretion of tubular injury biomarkers could be used as an additional non-invasive sensitive diagnostic tool to identify unrecognizable tubular damage and risk of long-term α-RLT nephrotoxicity., Methods: A bifunctional cyclic peptide, melanocortin 1 ligand (MC1L), labeled with [ 203 Pb]Pb-MC1L, was used for [ 212 Pb]Pb-MC1L biodistribution and absorbed dose measurements in CD-1 Elite mice. Mice were treated with [ 212 Pb]Pb-MC1L in a dose-escalation study up to levels of radioactivity intended to induce kidney injury. The approach enabled prospective kidney functional and injury biomarker evaluation and late kidney histological analysis to validate these biomarkers., Results: Biodistribution analysis identified [ 212 Pb]Pb-MC1L reabsorption in kidneys with a dose deposition of 2.8, 8.9, and 20 Gy for 0.9, 3.0, and 6.7 MBq injected [ 212 Pb]Pb-MC1L doses, respectively. As expected, mice receiving 6.7 MBq had significant weight loss and CKD evidence based on serum creatinine, cystatin C, and kidney histological alterations 28 weeks after treatment. A dose-dependent urinary neutrophil gelatinase-associated lipocalin (NGAL, tubular injury biomarker) urinary excretion the day after [ 212 Pb]Pb-MC1L treatment highly correlated with the severity of late tubulointerstitial injury and histological findings., Conclusion: Urine NGAL secretion could be a potential early diagnostic tool to identify unrecognized tubular damage and predict long-term α-RLT-related nephrotoxicity., (© 2023. The Author(s).)

This review article explores the evolving landscape of Molecular Radiotherapy (MRT), emphasizing Peptide Receptor Radionuclide Therapy (PRRT) for neuroendocrine tumours (NETs). The primary focus is on the transition from β-emitting radiopharmaceuticals to α-emitting agents in PRRT, offering a critical analysis of the radiobiological basis, clinical applications, and ongoing developments in Targeted Alpha Therapy (TAT). Through an extensive literature review, the article delves into the mechanisms and effectiveness of PRRT in targeting somatostatin subtype 2 receptors, highlighting both its successes and limitations. The discussion extends to the emerging paradigm of TAT, underlining its higher potency and specificity with α-particle emissions, which promise enhanced therapeutic efficacy and reduced toxicity. The review critically evaluates preclinical and clinical data, emphasizing the need for standardised dosimetry and a deeper understanding of the dose-response relationship in TAT. The review concludes by underscoring the significant potential of TAT in treating SSTR2-overexpressing cancers, especially in patients refractory to β-PRRT, while also acknowledging the current challenges and the necessity for further research to optimize treatment protocols.

Purpose: The lead-203 ( 203 Pb)/lead-212 ( 212 Pb) elementally identical radionuclide pair has gained significant interest in the field of image-guided targeted alpha-particle therapy for cancer. Emerging evidence suggests that 212 Pb-labeled peptide-based radiopharmaceuticals targeting somatostatin receptor subtype 2 (SSTR2) may provide improved effectiveness compared to beta-particle-based therapies for neuroendocrine tumors (NETs). This study aims to improve the performance of SSTR2-targeted radionuclide imaging and therapy through structural modifications to Tyr 3 -octreotide (TOC)-based radiopharmaceuticals., Methods: New SSTR2-targeted peptides were designed and synthesized with the goal of optimizing the incorporation of Pb isotopes through the use of a modified cyclization technique; the introduction of a Pb-specific chelator (PSC); and the insertion of polyethylene glycol (PEG) linkers. The binding affinity of the peptides and the cellular uptake of 203 Pb-labeled peptides were evaluated using pancreatic AR42J (SSTR2+) tumor cells and the biodistribution and imaging of the 203 Pb-labeled peptides were assessed in an AR42J tumor xenograft mouse model. A lead peptide was identified (i.e., PSC-PEG 2 -TOC), which was then further evaluated for efficacy in 212 Pb therapy studies., Results: The lead radiopeptide drug conjugate (RPDC) - [ 203 Pb]Pb-PSC-PEG 2 -TOC - significantly improved the tumor-targeting properties, including receptor binding and tumor accumulation and retention as compared to [ 203 Pb]Pb-DOTA 0 -Tyr 3 -octreotide (DOTATOC). Additionally, the modified RPDC exhibited faster renal clearance than the DOTATOC counterpart. These advantageous characteristics of [ 212 Pb]Pb-PSC-PEG 2 -TOC resulted in a dose-dependent therapeutic effect with minimal signs of toxicity in the AR42J xenograft model. Fractionated administrations of 3.7 MBq [ 212 Pb]Pb-PSC-PEG 2 -TOC over three doses further improved anti-tumor effectiveness, resulting in 80% survival (70% complete response) over 120 days in the mouse model., Conclusion: Structural modifications to chelator and linker compositions improved tumor targeting and pharmacokinetics (PK) of 203/212 Pb peptide-based radiopharmaceuticals for NET theranostics. These findings suggest that PSC-PEG 2 -TOC is a promising candidate for Pb-based targeted radionuclide therapy for NETs and other types of cancers that express SSTR2., (© 2023. The Author(s).)

Targeted alpha therapy (TAT) using lead-212 (Pb-212)-labeled peptides presents an attractive option for the treatment of metastatic neuroendocrine tumors (NETs). As Pb-203 presents an accurate diagnostic surrogate to Pb-212, imaging with Pb-203-labelled peptides can be an important prerequisite to assess the feasibility of TAT with Pb-212-labelled agents. Here, we present the imaging data of a patient with metastatic NET with Pb-203 VMT-α-NET, a somatostatin receptor targeting agent, and demonstrate the matching distribution of Pb-203 VMT-α-NET with Ga-68 DOTANOC., Competing Interests: There are no conflicts of interest., (Copyright: © 2024 Indian Journal of Nuclear Medicine.)

Although pancreatic ductal adenocarcinoma (PDAC) is associated with limited treatment options and poor patient outcomes, targeted α-particle therapy (TAT) represents a promising development in the field. TAT shows potential in treating metastatic cancers, including those that have become resistant to conventional treatments. Among the most auspicious radionuclides stands the in vivo α-generator 212 Pb. Combined with the imaging-compatible radionuclide 203 Pb, this theranostic match is a promising modality rapidly translating into the clinic. Methods: Using the pretargeting approach between a radiolabeled 1,2,4,5-tetrazine (Tz) tracer and a trans -cyclooctene (TCO) modified antibody, imaging and therapy with radiolead were performed on a PDAC tumor xenograft mouse model. For therapy, 3 cohorts received a single administration of 1.1, 2.2, or 3.7 MBq of the pretargeting agent, [ 212 Pb]Pb-DO3A-PEG 7 -Tz, whereby administered activity levels were guided by dosimetric analysis. Results: The treated mice were holistically evaluated; minimal-to-mild renal tubular necrosis was observed. At the same time, median survival doubled for the highest-dose cohort (10.7 wk) compared with the control cohort (5.1 wk). Conclusion: This foundational study demonstrated the feasibility and safety of pretargeted TAT with 212 Pb in PDAC while considering dose limitations and potential adverse effects., (© 2024 by the Society of Nuclear Medicine and Molecular Imaging.)

(1) Background: In neuroendocrine tumors (NETs), somatostatin receptor subtype 2 is highly expressed, which can be targeted by a radioactive ligand such as [ 177 Lu]Lu-1,4,7,10-tetraazacyclododecane- N , N ', N ″, N ‴,-tetraacetic acid-[Tyr 3 ,Thr 8 ]-octreotide ( 177 Lu-DOTA-TOC) and, more recently, by a lead specific chelator (PSC) containing 203/212 Pb-PSC-PEG 2 -TOC (PSC-TOC). The molar activity (A M ) can play a crucial role in tumor uptake, especially in receptor-mediated uptake, such as in NETs. Therefore, an investigation of the influence of different molar activities of 203/212 Pb-PSC-TOC on cell uptake was investigated. (2) Methods: Optimized radiolabeling of 203/212 Pb-PSC-TOC was performed with 50 µg of precursor in a NaAc/AcOH buffer at pH 5.3-5.5 within 15-45 min at 95° C. Cell uptake was studied in AR42 J, HEK293 sst2, and ZR75-1 cells. (3) Results: 203/212 Pb-PSC-TOC was radiolabeled with high radiochemical purity >95% and high radiochemical yield >95%, with A M ranging from 0.2 to 61.6 MBq/nmol. The cell uptake of 203 Pb-PSC-TOC (A M = 38 MBq/nmol) was highest in AR42 J (17.9%), moderate in HEK293 sstr (9.1%) and lowest in ZR75-1 (0.6%). Cell uptake increased with the level of A M . (4) Conclusions: A moderate A M of 15-40 MBq/nmol showed the highest cell uptake. No uptake limitation was found in the first 24-48 h. Further escalation experiments with even higher A M should be performed in the future. It was shown that A M plays an important role because of its direct dependence on the cellular uptake levels, possibly due to less receptor saturation with non-radioactive ligands at higher A M .

203 Pb is a surrogate imaging match for 212 Pb. This elementally matched pair is emerging as a suitable pair for imaging and targeted radionuclide therapy in cancer care. Because of the half-life (51.9 h) and low-energy γ-rays emitted, 203 Pb is suitable for the development of diagnostic radiopharmaceuticals. The aim of this work was to optimize the production and separation of high-specific-activity 203 Pb using electroplated thallium targets. We further investigated the radiochemistry optimization using a suitable chelator, tetraazacyclododecane-1,4,7-triacetic acid (DO3A), and targeting vector, VMT-α-NET (lead-specific chelator conjugated to tyr3-octreotide via a polyethylene glycol linker). Methods: Targets were prepared by electroplating of natural or enriched ( 205 Tl) thallium metal. Scanning electron microscopy was performed to determine the structure and elemental composition of electroplated targets. Targets were irradiated with 24-MeV protons with varying current and beam time to investigate target durability. 203 Pb was purified from the thallium target material using an extraction resin (lead resin) column followed by a second column using a weak cation-exchange resin to elute the lead isotope as [ 203 Pb]PbCl 2 Inductively coupled plasma mass spectrometry studies were used to further characterize the separation for trace metal contaminants. Radiolabeling efficiency was also investigated for DO3A chelator and VMT-α-NET (a peptide-based targeting conjugate). Results: Electroplated targets were prepared at a high plating density of 76-114 mg/cm 2 using a plating time of 5 h. A reproducible separation method was established with a final elution in HCl (400 μL, 1 M) suitable for radiolabeling. Greater than 90% recovery yields were achieved, with an average specific activity of 37.7 ± 5.4 GBq/μmol (1.1 ± 0.1 Ci/μmol). Conclusion: An efficient electroplating method was developed to prepare thallium targets suitable for cyclotron irradiation. A simple and fast separation method was developed for routine 203 Pb production with high recovery yields and purity., (© 2023 by the Society of Nuclear Medicine and Molecular Imaging.)

203 Pb and 212 Pb have emerged as promising theranostic isotopes for image-guided α-particle radionuclide therapy for cancers. Here, we report a cyclen-based Pb specific chelator (PSC) that is conjugated to tyr 3 -octreotide via a PEG 2 linker (PSC-PEG-T) targeting somatostatin receptor subtype 2 (SSTR2). PSC-PEG-T could be labeled efficiently to purified 212 Pb at 25 °C and also to 212 Bi at 80 °C. Efficient radiolabeling of mixed 212 Pb and 212 Bi in PSC-PEG-T was also observed at 80 °C. Post radiolabeling, stable Pb(II) and Bi(III) radiometal complexes in saline were observed after incubating [ 203 Pb]Pb-PSC-PEG-T for 72 h and [ 212 Bi]Bi-PSC-PEG-T for 5 h. Stable [ 212 Pb]Pb-PSC-PEG-T and progeny [ 212 Bi]Bi-PSC-PEG-T were identified after storage in saline for 24 h. In serum, stable radiometal/radiopeptide were observed after incubating [ 203 Pb]Pb-PSC-PEG-T for 55 h and [ 212 Pb]Pb-PSC-PEG-T for 24 h. In vivo biodistribution of [ 212 Pb]Pb-PSC-PEG-T in tumor-free CD-1 Elite mice and athymic mice bearing AR42J xenografts revealed rapid tumor accumulation, excellent tumor retention and fast renal clearance of both 212 Pb and 212 Bi, with no in vivo redistribution of progeny 212 Bi. Single-photon emission computed tomography (SPECT) imaging of [ 203 Pb]Pb-PSC-PEG-T and [ 212 Pb]Pb-PSC-PEG-T in mice also demonstrated comparable accumulation in AR42J xenografts and renal clearance, confirming the theranostic potential of the elementally identical 203 Pb/ 212 Pb radionuclide pair.

Abstract: In an end-stage midgut neuroendocrine tumor patient with carcinoid heart disease, right ventricular dysfunction, mildly reduced renal function, and refractory to 6 cycles of 177 Lu-HA-DOTATATE therapy, planar, and 22 hours SPECT/CT images were acquired after injection of 224 MBq of 203 Pb-VMT-α-NET to assess the feasibility of performing 212 Pb-VMT-α-NET therapy. A comparison of the 1.5 and 22 hours SPECT/CT images with 68 Ga-HA-DOTATATE PET/CT showed high uptake of 203 Pb-VMT-α-NET in liver metastases matching with the results of the PET/CT investigation., Competing Interests: Conflicts of interest and sources of funding: The author M.K.S. is inventor of the peptide VMT-α-NET and CSO (Chief Science Officer) of Viewpoint Molecular Targeting, Inc. There is no conflict of interest with respect to the other authors. The radiopharmaceutical 203 Pb-VMT-α-NET was manufactured under cGMP conditions and applied in accordance with the German National Law (§13 [2b] AMG)., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc.)

Introduction: 203 Pb (t 1/2  = 51.9 h, 279 keV (81 %)) is a diagnostic SPECT imaging radionuclide ideally suited for theranostic applications in combination with 212 Pb for targeted alpha particle therapy. Our objectives were to develop a high-yield solid target 203 Pb cyclotron production route using isotopically enriched 205 Tl target material and the 205 Tl(p,3n) 203 Pb reaction as an alternative to lower energy production via the 203 Tl(p,n) 203 Pb reaction., Methods: 250 mg 205 Tl metal (99.9 % isotopic enrichment) was pressed using a hardened stainless steel die. Aluminum target discs were machined with a central depression and annulus groove. The flattened 205 Tl pellet was placed into the central depression of the Al disc and a circle of indium wire was laid in the machined annulus surrounding the pellet. An aluminum foil cover was then pressed onto the target disc to create an airtight bond. Targets were irradiated at 23.3 MeV for up to 516 min on a TR-24 cyclotron at currents up to 60 μA to produce 203 Pb via the 205 Tl(p,3n) 203 Pb nuclear reaction. Following a cool-down period of >12 h, the target was removed and 205 Tl dissolved in 4 M HNO 3 . A NEPTIS Mosaic-LC synthesis unit performed automated separation using Eichrom Pb resin, and 203 Pb was eluted using 8 M HCl or 1 M NH 4 OAc. 205 Tl was diverted to a vial for recovery in an electrolytic cell. 203 Pb product radionuclidic purity was assessed by HPGe gamma spectroscopy, while elemental purity was assessed by ICP-OES. Radiolabeling and stability studies were performed with PSC, TCMC, and DOTA chelators, and 203 Pb incorporation was verified by radio-TLC analysis., Results: Cyclotron irradiations performed at 60 μA proton beam current and 23.3 MeV ( 205 Tl incident energy) had a 203 Pb saturated yield of 4658 ± 62 MBq/μA (n = 3). Automated NEPTIS separation took <4 h from the start of target dissolution to product elution, yielding >85 % decay-corrected [ 203 Pb]PbCl 2 with a radionuclidic purity of >99.9 %. Purified [ 203 Pb]PbCl 2 yields of up to 12 GBq 203 Pb were attained (15.8 GBq at EOB). The [ 203 Pb]PbCl 2 and [ 203 Pb]Pb(OAc) 2 products contained no detectable radionuclidic impurities besides 201 Pb (<0.1 %), and <0.4 ppm stable Pb. 205 Tl metal was recovered with a 92 % batch yield. Aliquots of 100 μL [ 203 Pb]Pb(OAc) 2 were used for radiolabeling PSC-Bn-NCS, TCMC-NCS, and DOTA-NCS chelators at pH 4.5 and 22 °C for 30 min, with maximum respective molar activities of 461 ± 30 GBq/μmol, 195 ± 37 GBq/μmol, and 83 ± 12 GBq/μmol. PSC, TCMC, and DOTA chelators exhibited >99.9 % incorporation after a 120-hour incubation in human serum at 37 °C., Conclusions: Nuclear medicine centers with access to higher energy cyclotrons can produce large 203 Pb activities sufficient for clinical applications, with a convenient separation technique producing highly pure [ 203 Pb]PbCl 2 or [ 203 Pb]Pb(OAc) 2 for direct radiolabeling. This represents an attractive route to produce 203 Pb for diagnostic SPECT imaging alongside 212 Pb targeted alpha particle therapy., Advances in Knowledge and Implications for Patient Care: Our high-yield 203 Pb production technique significantly enhances 203 Pb production capabilities to meet the growing preclinical and clinical demand for 203 Pb radiopharmaceuticals alongside 212 Pb target alpha particle therapy., Competing Interests: Declaration of competing interest The authors have filed a patent application for the described sealed target technology., (Copyright © 2023 Elsevier Inc. All rights reserved.)

[ 212 Pb]VMT01 is a melanocortin 1 receptor (MC1R) targeted theranostic ligand in clinical development for alpha particle therapy for melanoma. 212 Pb has an elementally matched gamma-emitting isotope 203 Pb; thus, [ 203 Pb]VMT01 can be used as an imaging surrogate for [ 212 Pb]VMT01. [ 212 Pb]VMT01 human serum stability studies have demonstrated retention of the 212 Bi daughter within the chelator following beta emission of parent 212 Pb. However, the subsequent alpha emission from the decay of 212 Bi into 208 Tl results in the generation of free 208 Tl. Due to the 10.64-hour half-life of 212 Pb, accumulation of free 208 Tl in the injectate will occur. The goal of this work is to estimate the human dosimetry for [ 212 Pb]VMT01 and the impact of free 208 Tl in the injectate on human tissue absorbed doses. Human [ 212 Pb]VMT01 tissue absorbed doses were estimated from murine [ 203 Pb]VMT01 biodistribution data, and human biodistribution values for 201 Tl chloride (a cardiac imaging agent) from published data were used to estimate the dosimetry of free 208 Tl. Results indicate that the dose-limiting tissues for [ 212 Pb]VMT01 are the red marrow and the kidneys, with estimated absorbed doses of 1.06 and 8.27 mGy RBE = 5 /MBq. The estimated percent increase in absorbed doses from free 208 Tl in the injectate is 0.03% and 0.09% to the red marrow and the kidneys, respectively. Absorbed doses from free 208 Tl result in a percent increase of no more than 1.2% over [ 212 Pb]VMT01 in any organ or tissue. This latter finding indicates that free 208 Tl in the [ 212 Pb]VMT01 injectate will not substantially impact estimated tissue absorbed doses in humans.

Gallium is a tri-valent p-block metal that closely mimics tri-valent iron. Gallium is internalized into cells via transferrin receptor-mediated endocytosis. Both Ga-67 and Ga-68 are radionuclides that can be radiolabeled to various bioactive compounds for clinical imaging procedures to visualize tumors and sites of inflammation. High-dose ascorbate (pharmacological ascorbate) is an emergent glioblastoma therapy that enhances cancer cell-killing through iron-metabolic perturbations. We hypothesized that pharmacological ascorbate treatments might alter Ga-67 uptake in glioblastoma cells. We evaluated the in vitro ability of pharmacological ascorbate to alter gallium uptake in patient-derived glioblastoma cells with variable genetic backgrounds by co-incubating cells with Ga-67 ± pharmacological ascorbate. Surprisingly, we observed increased basal gallium uptake in the glioblastoma cells compared to normal human astrocytes. Further, pharmacological ascorbate treatment stimulated gallium uptake in glioblastoma cells while not affecting uptake in normal human astrocytes. This effect appears to be related to transient increases in transferrin receptor expression. Finally, pharmacological ascorbate treatment appears to stimulate gallium uptake in an iron metabolism-dependent manner. Further mechanistic experiments are required to evaluate the translational utility of ascorbate to impact gallium tumor imaging., Competing Interests: Conflict of interest None.

Radiotherapy can facilitate the immune recognition of immunologically "cold" tumors and enhance the efficacy of anti-PD-1 and anti-CTLA-4 immune checkpoint inhibitors (ICIs) in melanoma. Systemic administration of receptor-targeted radionuclide therapy has the potential to selectively deliver radionuclides to multiple tumors throughout the body in metastatic settings. By triggering immunologic cell death and increasing the immune susceptibility of surviving tumor cells in these locations, targeted radionuclide therapies may overcome resistance to ICIs and render immunologically "cold" tumors throughout the body responsive to ICIs and immunologically "hot". Here, we show the anti-tumor cooperation of targeted α-particle radionuclide therapy (α-TRT) and ICIs in preclinical models of melanoma. Melanocortin 1 receptor (MC1R)-targeted radiopeptide [ 212 Pb]VMT01 was employed to deliver α-radiation to melanoma tumors in mice. A single injection of 4.1 MBq [ 212 Pb]VMT01 significantly slowed the tumor growth of B16-F10 melanoma and the combination of [ 212 Pb]VMT01 and ICIs induced a cooperative anti-tumor effect leading to 43% complete tumor response with no sign of malignancy on autopsy. Animals with complete response developed anti-tumor immunity to reject further tumor inoculations. This therapeutic cooperation was completely abolished in RAG1 KO mice, which are deficient in T-cell maturation. In addition, the anti-tumor cooperation was compromised when fractionated [ 212 Pb]VMT01 was used in the combination. We also demonstrated that [ 212 Pb]VMT01 induced immunogenic cell death in tumor vaccination assays and in vitro exposure to [ 212 Pb]VMT01 sensitized immunotolerant melanoma to ICIs treatment in vivo. Enhanced tumor infiltrating CD3 + , CD4 + , CD8 + lymphocytes were observed following injection of 1.4 MBq [ 212 Pb]VMT01. Overall, we demonstrated anti-tumor cooperation between α-TRT and ICIs in melanoma that is mediated by tumor specific immunity.

Dihydroartemisinin (DHA) is an FDA-approved antimalarial drug that has been repurposed for cancer therapy because of its preferential antiproliferative effects on cancer versus normal cells. Mitochondria represent an attractive target for cancer therapy based on their regulatory role in proliferation and cell death. This study investigates whether DHA conjugated to innately fluorescent N-alkyl triphenylvinylpyridinium (TPVP) perturbs mitochondrial functions resulting in a differential toxicity of cancer versus normal cells. TPVP-DHA treatments resulted in a dose-dependent toxicity of human melanoma and pancreatic cancer cells, whereas normal human fibroblasts were resistant to this treatment. TPVP-DHA treatments resulted in a G 1 -delay of the cancer cell cycle, which was also associated with a significant inhibition of the mTOR-metabolic and ERK1/2-proliferative signaling pathways. TPVP-DHA treatments perturbed mitochondrial functions, which correlated with increases in mitochondrial fission. In summary, TPVP mediated mitochondrial targeting of DHA enhanced cancer cell toxicity by perturbing mitochondrial functions and morphology., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Radiation oncologists and nuclear medicine physicians have seen a resurgence in the clinical use of radiopharmaceuticals for the curative or palliative treatment of cancer. To enable the discovery and the development of new targeted radiopharmaceutical treatments, the United States National Cancer Institute has adapted its clinical trial enterprise to accommodate the requirements of a development program with investigational agents that have a radioactive isotope as part of the studied drug product. One change in perspective has been the consideration of investigational radiopharmaceuticals as drugs, with maximum tolerable doses determined by normal organ toxicity frequency like in drug clinical trials. Other changes include new clinical trial enterprise elements for biospecimen handling, adverse event reporting, regulatory conduct, writing services, drug master files, and reporting of patient outcomes. Arising from this enterprise, the study and clinical use of alpha-particle and beta-particle emitters have emerged as an important approach to cancer treatment. Resources allocated to this enterprise have brought forward biomarkers of molecular pathophysiology now used to select treatment or to evaluate clinical performance of radiopharmaceuticals. The clinical use of diagnostic and therapeutic radionuclide pairs is anticipated to accelerate radiopharmaceutical clinical development., (Published by Elsevier Inc.)

Despite dramatic improvements in outcomes arising from the introduction of targeted therapies and immunotherapies, metastatic melanoma is a highly resistant form of cancer with 5 year survival rates of <35%. Drug resistance is frequently reported to be associated with changes in oxidative metabolism that lead to malignancy that is non-responsive to current treatments. The current report demonstrates that triphenylphosphonium(TPP)-based lipophilic cations can be utilized to induce cytotoxicity in pre-clinical models of malignant melanoma by disrupting mitochondrial metabolism. In vitro experiments demonstrated that TPP-derivatives modified with aliphatic side chains accumulated in melanoma cell mitochondria; disrupted mitochondrial metabolism; led to increases in steady-state levels of reactive oxygen species; decreased total glutathione; increased the fraction of glutathione disulfide; and caused cell killing by a thiol-dependent process that could be rescued by N-acetylcysteine. Furthermore, TPP-derivative-induced melanoma toxicity was enhanced by glutathione depletion (using buthionine sulfoximine) as well as inhibition of thioredoxin reductase (using auranofin). In addition, there was a structure-activity relationship between the aliphatic side-chain length of TPP-derivatives (5-16 carbons), where longer carbon chains increased melanoma cell metabolic disruption and cell killing. In vivo bio-distribution experiments showed that intratumoral administration of a C14-TPP-derivative (12-carbon aliphatic chain), using a slow-release thermosensitive hydrogel as a delivery vehicle, localized the drug at the melanoma tumor site. There, it was observed to persist and decrease the growth rate of melanoma tumors. These results demonstrate that TPP-derivatives selectively induce thiol-dependent metabolic oxidative stress and cell killing in malignant melanoma and support the hypothesis that a hydrogel-based TPP-derivative delivery system could represent a therapeutic drug-delivery strategy for melanoma., Competing Interests: The authors have declared that no competing interests exist.

Therapies for lung cancer patients initially elicit desirable responses, but the presence of hypoxia and drug resistant cells within tumors ultimately lead to treatment failure. Disulfiram (DSF) is an FDA approved, copper chelating agent that can target oxidative metabolic frailties in cancer vs. normal cells and be repurposed as an adjuvant to cancer therapy. Clonogenic survival assays showed that DSF (50-150 nM) combined with physiological levels of Cu (15 μM CuSO 4 ) was selectively toxic to H292 NSCLC cells vs. normal human bronchial epithelial cells (HBEC). Furthermore, cancer cell toxicity was exacerbated at 1% O 2 , relative to 4 or 21% O 2 . This selective toxicity of DSF/Cu was associated with differential Cu ionophore capabilities. DSF/Cu treatment caused a >20-fold increase in cellular Cu in NSCLCs, with nearly two-fold higher Cu present in NSCLCs vs. HBECs and in cancer cells at 1% O 2 vs. 21% O 2 . DSF toxicity was shown to be dependent on the retention of Cu as well as oxidative stress mechanisms, including the production of superoxide, peroxide, lipid peroxidation, and mitochondrial damage. DSF was also shown to selectively (relative to HBECs) enhance radiation and chemotherapy-induced NSCLC killing and reduce radiation and chemotherapy resistance in hypoxia. Finally, DSF decreased xenograft tumor growth in vivo when combined with radiation and carboplatin. These results support the hypothesis that DSF could be a promising adjuvant to enhance cancer therapy based on its apparent ability to selectively target fundamental differences in cancer cell oxidative metabolism., Competing Interests: Declaration of competing interest Douglas R. Spitz PhD and Bryan G. Allen MD PhD have a sponsored research agreement with Galera Therapeutics, Inc. at the University of Iowa and are unpaid scientific consultants for Galera Therapeutics., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Receptor-targeted image-guided Radionuclide Therapy (TRT) is increasingly recognized as a promising approach to cancer treatment. In particular, the potential for clinical translation of receptor-targeted alpha-particle therapy is receiving considerable attention as an approach that can improve outcomes for cancer patients. Higher Linear-energy Transfer (LET) of alpha-particles (compared to beta particles) for this purpose results in an increased incidence of double-strand DNA breaks and improved-localized cancer-cell damage. Recent clinical studies provide compelling evidence that alpha-TRT has the potential to deliver a significantly more potent anti-cancer effect compared with beta-TRT. Generator-produced 212Pb (which decays to alpha emitters 212Bi and 212Po) is a particularly promising radionuclide for receptor-targeted alpha-particle therapy. A second attractive feature that distinguishes 212Pb alpha-TRT from other available radionuclides is the possibility to employ elementallymatched isotope 203Pb as an imaging surrogate in place of the therapeutic radionuclide. As direct non-invasive measurement of alpha-particle emissions cannot be conducted using current medical scanner technology, the imaging surrogate allows for a pharmacologically-inactive determination of the pharmacokinetics and biodistribution of TRT candidate ligands in advance of treatment. Thus, elementally-matched 203Pb labeled radiopharmaceuticals can be used to identify patients who may benefit from 212Pb alpha-TRT and apply appropriate dosimetry and treatment planning in advance of the therapy. In this review, we provide a brief history on the use of these isotopes for cancer therapy; describe the decay and chemical characteristics of 203/212Pb for their use in cancer theranostics and methodologies applied for production and purification of these isotopes for radiopharmaceutical production. In addition, a medical physics and dosimetry perspective is provided that highlights the potential of 212Pb for alpha-TRT and the expected safety for 203Pb surrogate imaging. Recent and current preclinical and clinical studies are presented. The sum of the findings herein and observations presented provide evidence that the 203Pb/212Pb theranostic pair has a promising future for use in radiopharmaceutical theranostic therapies for cancer., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

This article investigated the efficacy of the combination of antiepileptic drug therapy in protecting against soman-induced seizure severity, epileptogenesis and performance deficits. Adult male rats with implanted telemetry transmitters for continuous recording of electroencephalographic (EEG) activity were exposed to soman and treated with atropine sulfate and the oxime HI-6 one minute after soman exposure and with midazolam, ketamine and/or valproic acid 40 min after seizure onset. Rats exposed to soman and treated with medical countermeasures were evaluated for survival, seizure severity, the development of spontaneous recurrent seizure and performance deficits; combination anti-epileptic drug therapy was compared with midazolam monotherapy. Telemetry transmitters were used to record EEG activity, and a customized MATLAB algorithm was used to analyze the telemetry data. Survival data, EEG power integral data, spontaneous recurrent seizure data and behavioral data are illustrated in figures and included as raw data. In addition, edf files of one month telemetry recordings from soman-exposed rats treated with delayed midazolam are provided as supplementary materials. Data presented in this article are related to research articles "Rational Polytherapy in the Treatment of Cholinergic Seizures" [1] and "Early polytherapy for benzodiazepine-refractory status epilepticus [4].

Melanocortin 1 receptor (MC1R) is under investigation as a target for drug delivery for metastatic melanoma therapy and imaging. The purpose of this study was to determine the potential of using BRAF inhibitors (BRAF i ) and histone deacetylase inhibitors (HDAC i ) to enhance the delivery of MC1R-targeted radiolabeled peptide ([ 212 Pb]DOTA-MC1L) by pharmacologically upregulating the MC1R expression in metastatic melanoma cells and tumors. MC1R expression was analyzed in de-identified melanoma biopsies by immunohistochemical staining. Upregulation of MC1R expression was determined in BRAF V600E cells (A2058) and BRAF wild-type melanoma cells (MEWO) by quantitative real-time polymerase chain reaction, flow cytometry, and receptor-ligand binding assays. The role of microphthalmia-associated transcription factor (MITF) in the upregulation of MC1R was also examined in A2058 and MEWO cells. The effectiveness of [ 212 Pb]DOTA-MC1L α-particle radiotherapy in combination with BRAF i and/or HDAC i was determined in athymic nu/nu mice bearing A2058 and MEWO human melanoma xenografts. High expression of MC1R was observed in situ in clinical melanoma biopsies. BRAF i and HDAC i significantly increased the MC1R expression (up to 10-fold in mRNA and 4-fold in protein levels) via MITF-dependent pathways, and this increase led to enhanced ligand binding on the cell surface. Inhibition of MITF expression antagonized the upregulation of MC1R in both BRAF V600E and BRAF WT cells. Combining [ 212 Pb]DOTA-MC1L with BRAF i and/or HDAC i improved the tumor response by increasing the delivery of 212 Pb α-particle emissions to melanoma tumors via augmented MC1R expression. These data suggest that FDA-approved HDAC i and BRAF i could improve the effectiveness of MC1R-targeted therapies by enhancing drug delivery via upregulated MC1R.

Pretherapy PET with 86 Y-DOTATOC is considered the ideal dosimetry protocol for 90 Y-DOTATOC therapy; however, its cost, limited availability, and need for infusion of amino acids to mimic the therapy administration limit its use in the clinical setting. The goal of this study was to develop a dosimetric method for 90 Y-DOTATOC using 90 Y-DOTATOC PET/CT and bremsstrahlung SPECT/CT and to determine whether dosimetry-based administered activities differ significantly from standard administered activities. Methods: This was a prospective phase 2 trial of 90 Y-DOTATOC therapy in patients with somatostatin receptor-positive tumors. 90 Y-DOTATOC was given in 3 cycles 6-8 wk apart. In the first cycle of therapy, adults received 4.4 GBq and children received 1.85 GBq/m 2 ; the subsequent administered activities were adjusted according to the dosimetry of the preceding cycle so as not to exceed a total kidney dose of 23 Gy and bone marrow dose of 2 Gy. The radiation dose to the kidneys was determined from serial imaging sessions consisting of time-of-flight 90 Y-DOTATOC PET/CT at 5 h after therapy and 90 Y-DOTATOC bremsstrahlung SPECT/CT at 6, 24, 48, and 72 h. The PET/CT data were used to measure the absolute concentration of 90 Y-DOTATOC and to calibrate the bremsstrahlung SPECT kidney clearance data. The radiation dose to the kidneys was determined by multiplying the time-integrated activity (from the fitted biexponential curve of renal clearance of 90 Y-DOTATOC) with the energy emitted per decay, divided by the mass of the kidneys. Results: The radiation dose to the kidneys per cycle of 90 Y-DOTATOC therapy was highly variable among patients, ranging from 0.32 to 3.0 mGy/MBq. In 17 (85%) of the 20 adult patients who received the second and the third treatment cycles of 90 Y-DOTATOC, the administered activity was modified by at least 20% from the starting administered activity. Conclusion: Renal dosimetry of 90 Y-DOTATOC is feasible using 90 Y-DOTATOC time-of-flight PET/CT and bremsstrahlung SPECT/CT and has a significant impact on the administered activity in treatment cycles., (© 2018 by the Society of Nuclear Medicine and Molecular Imaging.)

In the present study, the effect of radiolabeling conditions on radiolabeling efficiency and achievable specific activity of a DOTA-conjugated highly-lipophilic peptide containing three disulfide cyclization bonds was examined. The peptide is designed to bind specifically (with high affinity) to cell-surface receptor guanylyl cyclase C (GCC), which is universally expressed by colorectal cancer cells. The effect of systematic variation of chemical parameters pH, mass of peptide, acetate buffer concentration (ionic strength), and inclusion of ethanol in the radiolabeling reaction vessel on achievable specific activity and labeling efficiency was examined. In addition, a unique approach to acetone-based elution of 68 Ga from an initial cation-exchange pre-concentration column is introduced, which improved radiochemical yield and radiochemical purity. For the evaluation of the acetone-based method, two different post-radiolabeling reverse-phase (C18) approaches to purify the final radiolabeled peptide were tested. These results revealed the potential for peptide degradation via the cleavage of disulfide cyclization bonds to form free thiols when using one of these C18 cartridges. The final optimized procedure enabled radiolabeling efficiency of greater than 99% and specific activity greater than 35 MBq/nmole in less than 30 min. The optimized parameters were amenable to the use of an automated 68 Ge/ 68 Ga generator and fluid-handling system for clinical production of the GCC receptor-specific [ 68 Ga]DOTA-MLN6907 peptide. The chemical characteristics of individual peptides govern the most appropriate radiolabeling conditions for the preparation of radiopharmaceuticals., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In Alzheimer's Disease (AD), tau pathology has a spatiotemporally distinct pattern of progressive spread along anatomically connected neural pathways. Extracellular tau in the brain interstitial space increases in response to neuronal activity suggesting that neural activity may also drive pathogenic tau spread. Here we tested the hypothesis that neuronal activity drives human Tau (hTau) release and trans-synaptic spread to neuroanatomically connected regions. We used AAV to overexpress wild type full-length hTau and an excitatory DREADD (Designer Receptors Exclusively Activated by a Designer Drug) in mouse primary hippocampal cultures and determined that excitatory stimulation with the DREADD ligand clozapine N-oxide (CNO) promoted extracellular hTau release. We translated this approach to an in vivo model and used AAV to express hTau and the excitatory DREADD in the ventral hippocampus of wild type mice, P301L hTau-expressing mice, or tau knockout mice. Six to eight weeks following AAV injection, we determined that CNO treatment in DREADD-expressing mice resulted in increased hTau pathology and hTau spread to distal brain regions compared to unstimulated controls (CNO in non-DREADD mice, or vehicle in DREADD mice). The results highlight a potentially disease relevant exacerbation of tau pathology in response to elevated neuronal activity. This model underscores the propensity of non-mutant hTau to undergo neuronal spreading, as seen in AD. The model can translate to other preclinical species and can be used to evaluate modes of tau transmission and test the efficacy of therapeutic approaches that target tau or hyperexcitability., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The use of targeted radionuclide therapy for cancer is on the rise. While beta-particle-emitting radionuclides have been extensively explored for targeted radionuclide therapy, alpha-particle-emitting radionuclides are emerging as effective alternatives. In this context, fundamental understanding of the interactions and dosimetry of these emitted particles with cells in the tumor microenvironment is critical to ascertaining the potential of alpha-particle-emitting radionuclides. One important parameter that can be used to assess these metrics is the S-value. In this study, we characterized several alpha-particle-emitting radionuclides (and their associated radionuclide progeny) regarding S-values in the cellular and tumor-metastasis environments. The Particle and Heavy Ion Transport code System (PHITS) was used to obtain S-values via Monte Carlo simulation for cell and tumor metastasis resulting from interactions with the alpha-particle-emitting radionuclides, lead-212 ( 212 Pb), actinium-225 ( 225 Ac) and bismuth-213 ( 213 Bi); these values were compared to the beta-particle-emitting radionuclides yttrium-90 ( 90 Y) and lutetium-177 ( 177 Lu) and an Auger-electron-emitting radionuclide indium-111 ( 111 In). The effect of cellular internalization on S-value was explored at increasing degree of internalization for each radionuclide. This aspect of S-value determination was further explored in a cell line-specific fashion for six different cancer cell lines based on the cell dimensions obtained by confocal microscopy. S-values from PHITS were in good agreement with MIRDcell S-values (cellular S-values) and the values found by Hindié et al. (tumor S-values). In the cellular model, 212 Pb and 213 Bi decay series produced S-values that were 50- to 120-fold higher than 177 Lu, while 225 Ac decay series analysis suggested S-values that were 240- to 520-fold higher than 177 Lu. S-values arising with 100% cellular internalization were two- to sixfold higher for the nucleus when compared to 0% internalization. The tumor dosimetry model defines the relative merit of radionuclides and suggests alpha particles may be effective for large tumors as well as small tumor metastases. These results from PHITS modeling substantiate emerging evidence that alpha-particle-emitting radionuclides may be an effective alternative to beta-particle-emitting radionuclides for targeted radionuclide therapy due to preferred dose-deposition profiles in the cellular and tumor metastasis context. These results further suggest that internalization of alpha-particle-emitting radionuclides via radiolabeled ligands may increase the relative biological effectiveness of radiotherapeutics.

This study examined water quality, naturally-occurring radioactive materials (NORM), major ions, trace metals, and well flow data for water used and produced from start-up to operation of an oil and gas producing hydraulically-fractured well (horizontal) in the Denver-Julesburg (DJ) Basin in northeastern Colorado. Analysis was conducted on the groundwater used to make the fracturing fluid, the fracturing fluid itself, and nine flowback/produced water samples over 220days of operation. The chemical oxygen demand of the wastewater produced during operation decreased from 8200 to 2500mg/L, while the total dissolved solids (TDS) increased in this same period from 14,200 to roughly 19,000mg/L. NORM, trace metals, and major ion levels were generally correlated with TDS, and were lower than other shale basins (e.g. Marcellus and Bakken). Although at lower levels, the salinity and its origin appear to be the result of a similar mechanism to that of other shale basins when comparing Cl/Br, Na/Br, and Mg/Br ratios. Volumes of returned wastewater were low, with only 3% of the volume injected (11millionliters) returning as flowback by day 15 and 30% returning by day 220. Low levels of TDS indicate a potentially treatment-amenable wastewater, but low volumes of flowback could limit onsite reuse in the DJ Basin. These results offer insight into the temporal water quality changes in the days and months following flowback, along with considerations and implications for water reuse in future hydraulic fracturing or for environmental discharge., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A method for preparation of Pb-212 and Pb-203 labeled chelator-modified peptide-based radiopharmaceuticals for cancer imaging and radionuclide therapy has been developed and adapted for automated clinical production. Pre-concentration and isolation of radioactive Pb2+ from interfering metals in dilute hydrochloric acid was optimized using a commercially-available Pb-specific chromatography resin packed in disposable plastic columns. The pre-concentrated radioactive Pb2+ is eluted in NaOAc buffer directly to the reaction vessel containing chelator-modified peptides. Radiolabeling was found to proceed efficiently at 85°C (45min; pH 5.5). The specific activity of radiolabeled conjugates was optimized by separation of radiolabeled conjugates from unlabeled peptide via HPLC. Preservation of bioactivity was confirmed by in vivo biodistribution of Pb-203 and Pb-212 labeled peptides in melanoma-tumor-bearing mice. The approach has been found to be robustly adaptable to automation and a cassette-based fluid-handling system (Modular Lab Pharm Tracer) has been customized for clinical radiopharmaceutical production. Our findings demonstrate that the Pb-203/Pb-212 combination is a promising elementally-matched radionuclide pair for image-guided radionuclide therapy for melanoma, neuroendocrine tumors, and potentially other cancers., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: Cardiac cachexia frequently accompanies the progression of heart failure despite the use of effective therapies for left ventricular dysfunction. Activation of the sympathetic nervous system has been implicated in the pathogenesis of weight loss, but the effects of sympathetic antagonism on cachexia are not well defined., Methods: We prospectively evaluated changes in body weight in 2289 patients with heart failure who had dyspnoea at rest or on minimal exertion and a left ventricular ejection fraction <25%. Patients were randomly assigned (double-blind) to receive either placebo (n = 1133) or carvedilol (n = 1156) and were followed for the occurrence of major clinical events for up to 29 months (COPERNICUS trial). Patients were not enrolled if they had signs of clinically significant fluid retention due to heart failure., Results: Patients in the carvedilol group were 33% less likely than patients in the placebo group to experience a further significant loss of weight (>6%) (95% confidence interval: 14-48%, P = 0.002) and were 37% more likely to experience a significant gain in weight (≥5%) (95% confidence interval: 12-66%, P = 0.002). Carvedilol's ability to prevent weight loss was most marked in patients with increased body mass index at baseline, whereas its ability to promote weight gain was most marked in patients with decreased body mass index at baseline. Increases in weight were not accompanied by evidence of fluid retention. Baseline values for body mass index and change in body weight were significant predictors of survival regardless of treatment., Conclusions: Carvedilol attenuated the development and promoted a partial reversal of cachexia in patients with severe chronic heart failure, supporting a role for prolonged sympathetic activation in the genesis of weight loss., (© 2017 The Authors. Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of the Society on Sarcopenia, Cachexia and Wasting Disorders.)

Determination of Pb-210 ( 210 Pb) in aqueous solution is a common radioanalytical challenge in environmental science. Widely used methods for undertaking these analyses (e.g., ASTM D7535) rely on the use of stable lead (Pb) as a yield tracer that takes into account losses of 210 Pb that inevitably occur during elemental/radiochemical separations of the procedures. Although effective, these methods introduce technical challenges that can be difficult to track and potentially introduce uncertainty that can be difficult to quantify. Examples of these challenges include interference from endogenous stable Pb in complex sample matrices; contamination of stable Pb carrier with 210 Pb; and high detection limits due to counting efficiency limitations. We hypothesized that many of these challenges could be avoided by the use of the electron-capture, gamma-emitting isotope, 203 Pb as a chemical yield tracer in the analysis of 210 Pb. A series of experiments were performed to evaluate the efficacy of 203 Pb as a tracer. Four different matrices were analyzed, including a complex matrix (hydraulic-fracturing produced fluids); and samples comprising less complicated matrices (i.e., river water, deionized water, and tap water). Separation techniques and counting methodologies were also compared and optimized. Due to a relatively short-half life (52 h), 203 Pb tracer is effectively massless for the purposes of chemical separations, allowing for reduced chromatography column resin bed volumes. Because 203 Pb is a gamma emitter (279 keV; 81% intensity), recovery can be determined non-destructively in a variety of matrices, including liquid scintillation cocktail. The use of liquid scintillation as a counting methodology allowed for determination of 210 Pb activities via 210 Pb or 210 Po; and recoveries of greater than 90% are routinely achievable using this approach. The improved method for the analysis of 210 Pb in aqueous matrices allows for the analysis of complex matrices, at reduced cost, while providing greater counting flexibility in achieving acceptable detections limits., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Coal is an integral part of global energy production; however, coal mining is associated with numerous environmental health impacts. It is well documented that coal-mine waste can contaminate the environment with naturally-occurring radionuclides from the uranium-238 ( 238 U) decay series. However, the behavior of the final radionuclide in the 238 U-series, i.e., polonium-210 ( 210 Po) arising from coal-mine waste-water discharge is largely unexplored. Here, results of a year-long (2014-2015) field study, in which the concentrations of 210 Po in sediments and surface water of a lake that receives coal-mine waste-water discharge in West Virginia are presented. Initial measurements identified levels of 210 Po in the lake sediments that were in excess of that which could be attributed to ambient U-series parent radionuclides; and were indicative of discharge site contamination of the lake ecosystem. However, control sediment obtained from a similar lake system in Iowa (an area with no coal mining or unconventional drilling) suggests that the levels of 210 Po in the lake are a natural phenomenon; and are likely unrelated to waste-water treatment discharges. Elevated levels of 210 Po have been reported in lake bottom sediments previously, yet very little information is available on the radioecological implications of 210 Po accumulation in lake bottom sediments. The findings of this study suggest that (Monthly Energy Review, 2016) the natural accumulation and retention of 210 Po in lake sediments may be a greater than previously considered (Chadwick et al., 2013) careful selection of control sites is important to prevent the inappropriate attribution of elevated levels of NORM in lake bottom ecosystems to industrial sources; and (Van Hook, 1979) further investigation of the source-terms and potential impacts on elevated 210 Po in lake-sediment ecosystems is warranted., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Therapeutic advances have markedly prolonged overall survival in multiple myeloma (MM) but the disease currently remains incurable. In a panel of MM cell lines (MM.1S, OPM-2, H929, and U266), using CD138 immunophenotyping, side population staining, and stem cell-related gene expression, we demonstrate the presence of stem-like tumor cells. Hypoxic culture conditions further increased CD138low stem-like cells with upregulated expression of OCT4 and NANOG. Compared to MM cells, these stem-like cells maintained lower steady-state pro-oxidant levels with increased uptake of the fluorescent deoxyglucose analog. In primary human MM samples, increased glycolytic gene expression correlated with poorer overall and event-free survival outcomes. Notably, stem-like cells showed increased mitochondrial mass, rhodamine 123 accumulation, and orthodox mitochondrial configuration while more condensed mitochondria were noted in the CD138high cells. Glycolytic inhibitor 2-deoxyglucose (2-DG) induced ER stress as detected by qPCR (BiP, ATF4) and immunoblotting (BiP, CHOP) and increased dihydroethidium probe oxidation both CD138low and CD138high cells. Treatment with a mitochondrial-targeting agent decyl-triphenylphosphonium (10-TPP) increased intracellular steady-state pro-oxidant levels in stem-like and mature MM cells. Furthermore, 10-TPP mediated increases in mitochondrial oxidant production were suppressed by ectopic expression of manganese superoxide dismutase. Relative to 2-DG or 10-TPP alone, 2-DG plus 10-TPP combination showed increased caspase 3 activation in MM cells with minimal toxicity to the normal hematopoietic progenitor cells. Notably, treatment with polyethylene glycol conjugated catalase significantly reduced 2-DG and/or 10-TPP-induced apoptosis of MM cells. Also, the combination of 2-DG with 10-TPP decreased clonogenic survival of MM cells. Taken together, this study provides a novel strategy of metabolic oxidative stress-induced cytotoxicity of MM cells via 2-DG and 10-TPP combination therapy., Competing Interests: The authors have declared that no competing interests exist.

Metastatic melanoma is the most aggressive and lethal form of skin cancer. Emerging evidence suggests that differences in melanoma metabolism relative to nonmalignant cells represent potential targets for improved therapy for melanoma. Specifically, melanoma cells exhibit increased mitochondrial electron transport chain (ETC) activity and concomitant hyperpolarized mitochondrial membrane potential relative to nonmalignant cells. We have synthesized several new fluorescent lipophilic vinylpyridinium cations built from tetraarylethylene scaffolds that target mitochondria via attraction to the hyperpolarized mitochondrial membrane potential. Mitochondria-specific accumulation in melanoma cells relative to normal human fibroblasts was demonstrated using confocal fluorescence microscopy and resulted in the disruption of oxidative metabolism leading to melanoma specific cell death in vitro. Thus, the pyridinium tetraarylethylene platform represents a promising new mitochondrial-targeted delivery vehicle with potential imaging and therapeutic properties.

Gallium-68 ((68)Ga) is a generator-produced radionuclide with a short half-life (t½ = 68 min) that is particularly well suited for molecular imaging by positron emission tomography (PET). Methods have been developed to synthesize (68)Ga-labeled imaging agents possessing certain drawbacks, such as longer synthesis time because of a required final purification step, the use of organic solvents or concentrated hydrochloric acid (HCl). In our manuscript, we provide a detailed protocol for the use of an advantageous sodium chloride (NaCl)-based method for radiolabeling of chelator-modified peptides for molecular imaging. By working in a lead-shielded hot-cell system,(68)Ga(3+) of the generator eluate is trapped on a cation exchanger cartridge (100 mg, ∼8 mm long and 5 mm diameter) and then eluted with acidified 5 M NaCl solution directly into a sodium acetate-buffered solution containing a DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) or DOTA-like chelator-modified peptide. The main advantages of this procedure are the high efficiency and the absence of organic solvents. It can be applied to a variety of peptides, which are stable in 1 M NaCl solution at a pH value of 3-4 during reaction. After labeling, neutralization, sterile filtration and quality control (instant thin-layer chromatography (iTLC), HPLC and pH), the radiopharmaceutical can be directly administered to patients, without determination of organic solvents, which reduces the overall synthesis-to-release time. This procedure has been adapted easily to automated synthesis modules, which leads to a rapid preparation of (68)Ga radiopharmaceuticals (12-16 min).

Naturally-occurring radioactive materials (NORM) associated with unconventional drilling produced fluids from the Marcellus Shale have raised environmental concerns. However, few investigations into the fundamental chemistry of NORM in Marcellus Shale produced fluids have been performed. Thus, we performed radiochemical experiments with Marcellus Shale produced fluids to understand the partitioning behavior of major radioelements of environmental health concern (uranium (U), thorium (Th), radium (Ra), lead (Pb), and polonium (Po)). We applied a novel radiotracer, (203)Pb, to understand the behavior of trace-levels of (210)Pb in these fluids. Ultrafiltration experiments indicated U, Th, and Po are particle reactive in Marcellus Shale produced fluids and Ra and Pb are soluble. Sediment partitioning experiments revealed that >99% of Ra does not adsorb to sediments in the presence of Marcellus Shale produced fluids. Further experiments indicated that although Ra adsorption is related to ionic strength, the concentrations of heavier alkaline earth metals (Ba, Sr) are stronger predictors of Ra solubility.

Introduction: 68Ga-DOTATATE is a radiolabeled peptide-based agonist that targets somatostatin receptors overexpressed in neuroendocrine tumors. Here, we present our results on validation of organic matrix 68Ge/68Ga generators (ITG GmbH) applied for radiosynthesis of the clinical doses of 68Ga-DOTATATE (GalioMedixTM)., Methods: The clinical grade of DOTATATE (25 μg±5 μg) compounded in 1 M NaOAc at pH=5.5 was labeled manually with 514±218 MBq (13.89±5.9 mCi) of 68Ga eluate in 0.05 N HCl at 95°C for 10 min. The radiochemical purity of the final dose was validated using radio-TLC. The quality control of clinical doses included tests of their osmolarity, endotoxin level, radionuclide identity, filter integrity, pH, sterility and 68Ge breakthrough., Results: The final dose of 272±126 MBq (7.35±3.4 mCi) of 68Ga-DOTATATE was produced with a radiochemical yield (RCY) of 99%±1%. The total time required for completion of radiolabeling and quality control averaged approximately 35 min. This resulted in delivery of 50%±7% of 68Ga-DOTATATE at the time of calibration (not decay corrected)., Conclusions: 68Ga eluted from the generator was directly applied for labeling of DOTA-peptide with no additional pre-concentration or pre-purification of isotope. The low acidity of 68Ga eluate allows for facile synthesis of clinical doses with radiochemical and radionuclide purity higher than 98% and average activity of 272±126 MBq (7.3±3 mCi). There is no need for post-labeling C18 Sep-Pak purification of final doses of radiotracer. Advances in knowledge and implications for patient care. The clinical interest in validation of 68Galabeled agents has increased in the past years due to availability of generators from different vendors (Eckert-Ziegler, ITG, iThemba), favorable approach of U.S. FDA agency to initiate clinical trials, and collaboration of U.S. centers with leading EU clinical sites. The list of 68Ga-labeled tracers evaluated in clinical studies should growth because of the sensitivity of PET technique, the simplicity of the shakebake approach for the dose preparation and reliability of 68Ge/68Ga generators. Our studies have confirmed the reproducible elution profile, and high reliability of ITG GmbH generators required for routine doses preparation according to FDA recommendations., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The potential sources of tritium input to the Yenisei River ecosystem are derived from local operations of nuclear facilities of the Mining and Chemical Combine operated by the state-owned Rosatom corporation and from sources derived from global weapons testing fallout and nuclear power. The background tritium concentrations in zoobenthos, bottom sediments, relevant commercial fish species, and widespread endogenous aquatic plants have been obtained for the first time in this region. Our results demonstrate that the major input term of tritium to this region of the Yenisei is derived from nearby mining operations of Rosatom, with tritium concentrations in aquatic plants marginally exceeding the observed background values obtained from upstream control sample collection sites.

The present study describes the optimization of (68)Ga radiolabeling with PAMAM dendrimer-DOTA conjugate. A conjugate (PAMAM-DOTA) concentration of 11.69µM, provided best radiolabeling efficiency of more than 93.0% at pH 4.0, incubation time of 30.0min and reaction temperature ranging between 90 and 100°C. The decay corrected radiochemical yield was found to be 79.4±0.01%. The radiolabeled preparation ([(68)Ga]-DOTA-PAMAM-D) remained stable (radiolabeling efficiency of 96.0%) at room temperature and in serum for up to 4-h. The plasma protein binding was observed to be 21.0%. After intravenous administration, 50.0% of the tracer cleared from the blood circulation by 30-min and less than 1.0% of the injected activity remained in blood by 1.0h. The animal biodistribution studies demonstrated that the tracer excretes through the kidneys and about 0.33% of the %ID/g accumulated in the tumor at 1h post injection. The animal organ's biodistribution data was supported by animal PET imaging showing good 'non-specific' tracer uptake in tumor and excretion is primarily through kidneys. Additionally, DOTA-PAMAM-D conjugation with αVβ3 receptors targeting peptides and drug loading on the dendrimers may improve the specificity of the (68)Ga labeled product for imaging and treating angiogenesis respectively., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Background: The economic value of unconventional natural gas resources has stimulated rapid globalization of horizontal drilling and hydraulic fracturing. However, natural radioactivity found in the large volumes of "produced fluids" generated by these technologies is emerging as an international environmental health concern. Current assessments of the radioactivity concentration in liquid wastes focus on a single element-radium. However, the use of radium alone to predict radioactivity concentrations can greatly underestimate total levels., Objective: We investigated the contribution to radioactivity concentrations from naturally occurring radioactive materials (NORM), including uranium, thorium, actinium, radium, lead, bismuth, and polonium isotopes, to the total radioactivity of hydraulic fracturing wastes., Methods: For this study we used established methods and developed new methods designed to quantitate NORM of public health concern that may be enriched in complex brines from hydraulic fracturing wastes. Specifically, we examined the use of high-purity germanium gamma spectrometry and isotope dilution alpha spectrometry to quantitate NORM., Results: We observed that radium decay products were initially absent from produced fluids due to differences in solubility. However, in systems closed to the release of gaseous radon, our model predicted that decay products will begin to ingrow immediately and (under these closed-system conditions) can contribute to an increase in the total radioactivity for more than 100 years., Conclusions: Accurate predictions of radioactivity concentrations are critical for estimating doses to potentially exposed individuals and the surrounding environment. These predictions must include an understanding of the geochemistry, decay properties, and ingrowth kinetics of radium and its decay product radionuclides.

Unconventional drilling (the combination of hydraulic fracturing and horizontal drilling) to extract oil and natural gas is expanding rapidly around the world. The rate of expansion challenges scientists and regulators to assess the risks of the new technologies on drinking water resources. One concern is the potential for subsurface drinking water resource contamination by naturally occurring radioactive materials co-extracted during unconventional drilling activities. Given the rate of expansion, opportunities to test drinking water resources in the pre- and post-fracturing setting are rare. This pilot study investigated the levels of natural uranium, lead-210, and polonium-210 in private drinking wells within 2000 m of a large-volume hydraulic fracturing operation--before and approximately one-year following the fracturing activities. Observed radionuclide concentrations in well waters tested did not exceed maximum contaminant levels recommended by state and federal agencies. No statistically-significant differences in radionuclide concentrations were observed in well-water samples collected before and after the hydraulic fracturing activities. Expanded monitoring of private drinking wells before and after hydraulic fracturing activities is needed to develop understanding of the potential for drinking water resource contamination from unconventional drilling and gas extraction activities., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Uranium-series dating techniques require the isolation of radionuclides in high yields and in fractions free of impurities. Within this context, we describe a novel-rapid method for the separation and purification of U, Th, and Pa. The method takes advantage of differences in the chemistry of U, Th, and Pa, utilizing a commercially-available extraction chromatographic resin (TEVA) and standard reagents. The elution behavior of U, Th, and Pa were optimized using liquid scintillation counting techniques and fractional purity was evaluated by alpha-spectrometry. The overall method was further assessed by isotope dilution alpha-spectrometry for the preliminary age determination of an ancient carbonate sample obtained from the Lake Bonneville site in western Utah (United States). Preliminary evaluations of the method produced elemental purity of greater than 99.99% and radiochemical recoveries exceeding 90% for U and Th and 85% for Pa. Excellent purity and yields (76% for U, 96% for Th and 55% for Pa) were also obtained for the analysis of the carbonate samples and the preliminary Pa and Th ages of about 39,000 years before present are consistent with (14)C-derived age of the material., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The progression of epileptiform activity following soman (GD) exposure is characterized by a period of excessive cholinergic activity followed by excessive glutamatergic activity resulting in status epilepticus, which may lead to neuropathological damage and behavioral deficits. Caramiphen edisylate is an anticholinergic drug with antiglutamatergic properties, which conceptually may be a beneficial therapeutic approach to the treatment of nerve agent exposure. In the present study, rats were exposed to 1.2 LD50 GD or saline, treated with atropine sulfate (2mg/kg, im) and HI-6 (93.6mg/kg, im) 1min after GD exposure, and monitored for seizure activity. Rats were treated with diazepam (10mg/kg, sc) and caramiphen (0, 20 or 100mg/kg, im) 30min after seizure onset. Following GD exposure, performance was evaluated using a battery of behavioral tests to assess motor coordination and function, sensorimotor gating, and cognitive function. Caramiphen as adjunct to diazepam treatment attenuated GD-induced seizure activity, neuropathological damage, and cognitive deficits compared to diazepam alone, but did not attenuate the GD-induced sensorimotor gating impairment. These findings show that physiological, behavioral, and neuropathological effects of GD exposure can be attenuated by treatment with caramiphen as an adjunct to therapy, even if administration is delayed to 30min after seizure onset., (Published by Elsevier Inc.)

Objective: To obtain information on practitioner experience in the use of the Genesys HydroThermAblator (HTA) System under normal clinical conditions through documentation of the system's acute safety features, in terms of burn rates, and its technical reliability., Study Design: This was a prospective, observational, multicenter, postmarket interventional clinical trial with outcome measures of acute (within 21 days post-procedure) safety, serious adverse device effects, and technical malfunctions in a population of premenopausal women > or = 18 years of age., Results: A total of 992 women (mean age, 41.7 +/- 6.8 years; range, 22-65 years) were enrolled in 18 clinical sites throughout the United States. The Genesys HTA System provided low burn rates in the intent-to-treat (n = 992 [0.4%] [95% CI 0.1-1.0%]) and evaluable (n = 931 [0.2%] [95% CI 0.1-0.8%]) subject populations. Only 1 burn was clinically significant and was defined as a serious adverse device effect (1/992 [0.10%] [95% CI 0.0-0.6%]). Fifty-three (5.1%) technical malfunctions occurred in 44 procedures, and 27 (27/44 [61.4%]) patients completed their procedures after 31 (31/ 53 [58.5%]) technical problems were addressed and resolved., Conclusion: The Genesys HTA System delivers a safe and reliable treatment option for premenopausal women with heavy menstrual bleeding.

Purpose: To propose a novel radiation therapy (RT) delivery modality: locally targeted delivery of micron-size RT sources by using temperature-sensitive hydrogel (RT-GEL) as an injectable vehicle., Methods and Materials: Hydrogel is a water-like liquid at room temperature but gels at body temperature. Two US Food and Drug Administration-approved polymers were synthesized. Indium-111 (In-111) was used as the radioactive RT-GEL source. The release characteristics of In-111 from polymerized RT-GEL were evaluated. The injectability and efficacy of RT-GEL delivery to human breast tumor were tested using animal models with control datasets of RT-saline injection. As proof-of-concept studies, a total of 6 nude mice were tested by injecting 4 million tumor cells into their upper backs after a week of acclimatization. Three mice were injected with RT-GEL and 3 with RT-saline. Single-photon emission computed tomography (SPECT) and CT scans were performed on each mouse at 0, 24, and 48 h after injection. The efficacy of RT-GEL was determined by comparison with that of the control datasets by measuring kidney In-111 accumulation (mean nCi/cc), representing the distant diffusion of In-111., Results: RT-GEL was successfully injected into the tumor by using a 30-gauge needle. No difficulties due to polymerization of hydrogel during injection and intratumoral pressure were observed during RT-GEL injection. No back flow occurred for either RT-GEL or RT-saline. The residual tumor activities of In-111 were 49% at 24 h (44% at 48 h, respectively) for RT-GEL and 29% (22%, respectively) for RT-saline. Fused SPECT-CT images of RT-saline showed considerable kidney accumulation of In-111 (2886%, 261%, and 262% of RT-GEL at 0, 24, and 48 h, respectively)., Conclusions: RT-GEL was successfully injected and showed much higher residual tumor activity: 170% (200%, respectively), than that of RT-saline at 24 h (48 h, respectively) after injection with a minimal accumulation of In-111 to the kidneys. Preliminary data of RT-GEL as a delivery modality of a radiation source to a local tumor are promising., (Published by Elsevier Inc.)