Imaging of 212Pb in mice with a clinical SPECT/CT.

INTRODUCTION: 212Pb is a promising radionuclide for targeted alpha therapy. Here, the feasibility of visualising the tumour uptake and biodistribution of 212Pb-NG001 in mice with a clinical SPECT/CT scanner was investigated. METHODS: A mouse phantom with 212Pb was imaged with a clinical- and a preclinical SPECT/CT scanner. Different acquisition and reconstruction settings were investigated on the clinical system (Siemens Symbia Intevo Bold). Two athymic nude mice carrying PC-3 PIP prostate cancer tumours of 235-830 µl received 1.44 MBq of 212Pb-NG001 and were imaged 2, 6, and 24 h post-injection on the clinical SPECT/CT with a Medium Energy collimator and a 40% energy window centred on 79 keV. All acquisition times were 30 min, except the mouse imaging 24 h post-injection which was 60 min. After the final imaging, the organs were harvested and measured on a gamma counter to give an indication of how much activity was present in organs of interest at the last imaging time point. RESULTS: Four volumes in the mouse phantom of ~ 300 µl with 246-303 kBq/ml of 212Pb were distinguishable on images acquired with the clinical SPECT/CT with a high number of reconstruction updates. With the preclinical SPECT, the same volumes were easily distinguished with 49 kBq/ml of 212Pb. Clinical SPECT/CT images of the mice revealed uptake in tumours and bladders 2 h after injection and in tumours containing down to approximately 15 kBq/ml at 6 and 24 h after injection. CONCLUSION: Although the preclinical scanner should be used preferentially in biodistribution studies in mice, the clinical SPECT/CT confirmed uptake in small volumes (e.g. ~ 300 µl volume with ~ 250 kBq/ml). Regardless of system, the resolution and sensitivity limits should be carefully determined, otherwise false negative or too low uptakes can be wrongly interpreted.

ALPL-1 is a target for chimeric antigen receptor therapy in osteosarcoma.

Osteosarcoma (OS) remains a dismal malignancy in children and young adults, with poor outcome for metastatic and recurrent disease. Immunotherapies in OS are not as promising as in some other cancer types due to intra-tumor heterogeneity and considerable off-target expression of the potentially targetable proteins. Here we show that chimeric antigen receptor (CAR) T cells could successfully target an isoform of alkaline phosphatase, ALPL-1, which is highly and specifically expressed in primary and metastatic OS. The target recognition element of the second-generation CAR construct is based on two antibodies, previously shown to react against OS. T cells transduced with these CAR constructs mediate efficient and effective cytotoxicity against ALPL-positive cells in in vitro settings and in state-of-the-art in vivo orthotopic models of primary and metastatic OS, without unexpected toxicities against hematopoietic stem cells or healthy tissues. In summary, CAR-T cells targeting ALPL-1 show efficiency and specificity in treating OS in preclinical models, paving the path for clinical translation.

Use of antihypertensive drugs and risk of cutaneous melanoma: a nationwide nested case-control study.

BACKGROUND: Most antihypertensives can induce dermal photosensitivity, which may increase melanoma risk. However, corroborating evidence is limited. We examined the associations between use of antihypertensives and melanoma risk. METHODS: A nationwide nested case-control study was conducted using data from the Cancer Registry of Norway, the National Registry and the Norwegian Prescription Database in 2004-15. Ten controls were randomly selected for each melanoma case, matched on sex and birth year. The study included 12 048 cases and 117 895 controls. We estimated rate ratios (RRs) with 95% confidence intervals (CIs). All analyses were adjusted for ambient ultraviolet radiation (UVR). We additionally performed active comparator analyses, and sensitivity analyses by only including new users, distinguishing between exclusive and mixed users, allowing for different latency periods, and subgroup analyses by melanoma subtype and clinical stage. RESULTS: Compared with non-use, we observed a slightly increased melanoma risk in users of diuretics (RR 1.08, CI 1.01-1.15), calcium-channel blockers (RR 1.10, CI 1.04-1.18) and drugs affecting the renin-angiotensin system (RR 1.10, CI 1.04-1.16), but not for beta blockers (RR 0.97, CI 0.92-1.03). We found no heterogeneity of associations by melanoma subtype or clinical stage and no dose-response relationship between the cumulative defined daily doses (DDDs) and melanoma. No interaction was found between cumulative DDDs and ambient UVR. CONCLUSIONS: Weak associations, with lack of a dose-response relationship and lack of interactions with ambient UVR, in the DDD analysis in this nationwide study do not support a causal relationship between antihypertensives and melanoma risk.

Targeted alpha therapy with the 224Ra/212Pb-TCMC-TP-3 dual alpha solution in a multicellular tumor spheroid model of osteosarcoma.

Osteosarcoma patients with overt metastases at primary diagnosis have a 5-year survival rate of less than 20%. TP-3 is a murine IgG2b monoclonal antibody with high affinity for an epitope residing on the p80 osteosarcoma cell surface membrane antigen. The tumor-associated antigen p80 is overexpressed in osteosarcomas, and has very low normal tissue expression. We propose a novel dual alpha targeting solution containing two radionuclides from the same decay chain, including the bone-seeking 224Ra, and cancer cell-surface seeking 212Pb-TCMC-TP-3 for the treatment of osteoblastic bone cancers, circulating cancer cells and micrometastases. In this in vitro study, the cytotoxic effects of 212Pb-TCMC-TP-3 (single alpha solution) and 224Ra/212Pb-TCMC-TP-3 (dual alpha solution) were investigated in a multicellular spheroid model mimicking micrometastatic disease in osteosarcoma. OHS spheroids with diameters of 253 ± 98 µm treated with 4.5, 2.7, and 3.3 kBq/ml of 212Pb-TCMC-TP-3 for 1, 4, and 24 h, respectively, were disintegrated within 3 weeks. The 212Pb-TCMC-TP-3 induced a 7-fold delay in spheroid doubling time compared to a 28-times higher dose with the non-specific 212Pb-TCMC-rituximab. The 224Ra/212Pb-TCMC-TP-3 completely disintegrated spheroids with diameters of 218-476 µm within 3 and 2 weeks after 4 and 24 h incubation with 5 kBq/ml, respectively. Treatment with 1 kBq/ml of 224Ra/212Pb-TCMC-TP-3 for 24 h caused an 11.4-fold reduction in spheroid viability compared with unconjugated 224Ra/212Pb. The single and dual alpha solutions with TP-3 showed cytotoxicity in spheroids of clinically relevant size, which warrant further testing of the dual alpha solution using in vivo osteosarcoma models.

Factors Influencing the Therapeutic Efficacy of the PSMA Targeting Radioligand 212Pb-NG001.

This study aimed to determine the influence of cellular PSMA expression, radioligand binding and internalization, and repeated administrations on the therapeutic effects of the PSMA-targeting radioligand 212Pb-NG001. Cellular binding and internalization, cytotoxicity, biodistribution, and the therapeutic efficacy of 212Pb-NG001 were investigated in two human prostate cancer cell lines with different PSMA levels: C4-2 (PSMA+) and PC-3 PIP (PSMA+++). Despite 10-fold higher PSMA expression on PC-3 PIP cells, cytotoxicity and therapeutic efficacy of the radioligand was only 1.8-fold better than for the C4-2 model, possibly explained by lower cellular internalization and less blood-rich stroma in PC-3 PIP xenografts. Mice bearing subcutaneous PC-3 PIP xenografts were treated with 0.2, 0.4, and 0.8 MBq of 212Pb-NG001 that resulted in therapeutic indexes of 2.7, 3.0, and 3.5, respectively. A significant increase in treatment response was observed in mice that received repeated injections compared to the corresponding single dose (therapeutic indexes of 3.6 for 2 × 0.2 MBq and 4.4 for 2 × 0.4 MBq). The results indicate that 212Pb-NG001 can induce therapeutic effects at clinically transferrable doses, both in the C4-2 model that resembles solid tumors and micrometastases with natural PSMA expression and in the PC-3 PIP model that mimics poorly vascularized metastases.

Dual targeting with 224Ra/212Pb-conjugates for targeted alpha therapy of disseminated cancers: A conceptual approach.

Metastases are the primary cause of death among cancer patients and efficacious new treatments are sorely needed. Targeted alpha-emitting radiopharmaceuticals that are highly cytotoxic may fulfill this critical need. The focus of this paper is to describe and explore a novel technology that may improve the therapeutic effect of targeted alpha therapy by combining two radionuclides from the same decay chain in the same solution. We hypothesize that the dual targeting solution containing bone-seeking 224Ra and cell-directed complexes of progeny 212Pb is a promising approach to treat metastatic cancers with bone and soft tissue lesions as well as skeletal metastases of mixed lytic/osteoblastic nature. A novel liquid 224Ra/212Pb-generator for rapid preparation of a dual targeting solution is described. Cancer cell targeting monoclonal antibodies, their fragments, synthetic proteins or peptides can all be radiolabeled with 212Pb in the 224Ra-solution in transient equilibrium with daughter nuclides. Thus, 224Ra targets stromal elements in sclerotic bone metastases and 212Pb-chelated-conjugate targets tumor cells of metastatic prostate cancer or osteosarcoma. The dual targeting solution may also be explored to treat metastatic breast cancer or multiple myeloma after manipulation of bone metastases to a more osteoblastic phenotype by the use of bisphosphonates, denosumab, bortezomib or hormone therapy prior to treatment. This may improve targeting of bone-seeking 224Ra and render an augmented radiation dose deposited within metastases. Our preliminary preclinical studies provide conceptual evidence that the dual 224Ra-solution with bone or tumor-targeted delivery of 212Pb has potential to inhibit cancer metastases without significant toxicity. In some settings, the use of a booster dose of purified 212Pb-conjugate alone could be required to elevate the effect of this tumor cell directed component, if needed, e.g., in a fractionated treatment regimen, where the dual targeting solution will act as maintenance treatment.

Evaluation of the PSMA-Binding Ligand 212Pb-NG001 in Multicellular Tumour Spheroid and Mouse Models of Prostate Cancer.

Radioligand therapy targeting the prostate-specific membrane antigen (PSMA) is rapidly evolving as a promising treatment for metastatic castration-resistant prostate cancer. The PSMA-targeting ligand p-SCN-Bn-TCMC-PSMA (NG001) labelled with 212Pb efficiently targets PSMA-positive cells in vitro and in vivo. The aim of this preclinical study was to evaluate the therapeutic potential of 212Pb-NG001 in multicellular tumour spheroid and mouse models of prostate cancer. The cytotoxic effect of 212Pb-NG001 was tested in human prostate C4-2 spheroids. Biodistribution at various time points and therapeutic effects of different activities of the radioligand were investigated in male athymic nude mice bearing C4-2 tumours, while long-term toxicity was studied in immunocompetent BALB/c mice. The radioligand induced a selective cytotoxic effect in spheroids at activity concentrations of 3-10 kBq/mL. In mice, the radioligand accumulated rapidly in tumours and was retained over 24 h, while it rapidly cleared from nontargeted tissues. Treatment with 0.25, 0.30 or 0.40 MBq of 212Pb-NG001 significantly inhibited tumour growth and improved median survival with therapeutic indexes of 1.5, 2.3 and 2.7, respectively. In BALB/c mice, no signs of long-term radiation toxicity were observed at activities of 0.05 and 0.33 MBq. The obtained results warrant clinical studies to evaluate the biodistribution, therapeutic efficacy and toxicity of 212Pb-NG001.

Improved Formulation of 224Ra-Labeled Calcium Carbonate Microparticles by Surface Layer Encapsulation and Addition of EDTMP.

Radium-224-labeled CaCO3 microparticles have been developed to treat peritoneal carcinomatosis. The microparticles function as carriers of 224Ra, facilitating intraperitoneal retention of the alpha-emitting radionuclide. It was necessary to control the size of microparticles in suspension over time and introduce a sterilization process for the clinical use of the radiopharmaceutical. Ethylenediamine tetra(methylene phosphonic acid) (EDTMP) was investigated as a stabilizing additive. The possibility of encapsulating the radiolabeled microparticles with an outer surface layer of CaCO3 for the improved retention of radioactivity by the carrier was studied. This work evaluated these steps of optimization and their effect on radiochemical purity, the biodistribution of radionuclides, and therapeutic efficacy. An EDTMP concentration of >1% (w/w) relative to CaCO3 stabilized the particle size for at least one week. Without EDTMP, the median particle size increased from ~5 µm to ~25 µm immediately after sterilization by autoclaving, and the larger microparticles sedimented rapidly in suspension. The percentage of adsorbed 224Ra progeny 212Pb increased from 56% to 94% at 2.4-2.5% (w/w) EDTMP when the 224Ra-labeled microparticles were layer-encapsulated. The improved formulation also resulted in a suitable biodistribution of radionuclides in mice, as well as a survival benefit for mice with intraperitoneal ovarian or colorectal tumors.

Preclinical and Clinical Status of PSMA-Targeted Alpha Therapy for Metastatic Castration-Resistant Prostate Cancer.

Bone, lymph node, and visceral metastases are frequent in castrate-resistant prostate cancer patients. Since such patients have only a few months' survival benefit from standard therapies, there is an urgent need for new personalized therapies. The prostate-specific membrane antigen (PSMA) is overexpressed in prostate cancer and is a molecular target for imaging diagnostics and targeted radionuclide therapy (theragnostics). PSMA-targeted α therapies (PSMA-TAT) may deliver potent and local radiation more selectively to cancer cells than PSMA-targeted ß- therapies. In this review, we summarize both the recent preclinical and clinical advances made in the development of PSMA-TAT, as well as the availability of therapeutic α-emitting radionuclides, the development of small molecules and antibodies targeting PSMA. Lastly, we discuss the potentials, limitations, and future perspectives of PSMA-TAT.

Combinatorial CAR design improves target restriction.

CAR T cells targeting the B lymphocyte antigen CD19 have led to remarkable clinical results in B cell leukemia and lymphoma but eliminate all B lineage cells, leading to increased susceptibility to severe infections. As malignant B cells will express either immunoglobulin (Ig) light chain κ or λ, we designed a second-generation CAR targeting Igκ, IGK CAR. This construct demonstrated high target specificity but displayed reduced efficacy in the presence of serum IgG. Since CD19 CAR is insensitive to serum IgG, we designed various combinatorial CAR constructs in order to maintain the CD19 CAR T cell efficacy, but with IGK CAR target selectivity. The Kz-19BB design, combining CD19 CAR containing a 4-1BB costimulatory domain with an IGK CAR containing a CD3zeta stimulatory domain, maintained the target specificity of IgK CAR and was resistant to the presence of soluble IgG. Our results demonstrate that a combinatorial CAR approach can improve target selectivity and efficacy.

Calcium Carbonate Microparticles as Carriers of 224Ra: Impact of Specific Activity in Mice with Intraperitoneal Ovarian Cancer.

BACKGROUND: Patients with advanced-stage ovarian cancer face a poor prognosis because of recurrent peritoneal cavity metastases following surgery and chemotherapy. Alpha-emitters may enable the efficient treatment of such disseminated diseases because of their short range and highly energetic radiation. Radium-224 is a candidate α-emitter due to its convenient 3.6-day half-life, with more than 90% of the decay energy originating from α-particles. However, its inherent skeletal accumulation must be overcome to facilitate intraperitoneal delivery of the radiation dose. Therefore, 224Ra-labeled CaCO3 microparticles have been developed. OBJECTIVE: The antitumor effect of CaCO3 microparticles as a carrier for 224Ra was investigated, with an emphasis on the ratio of activity to mass dose of CaCO3, that is, specific activity. METHODS: Nude athymic mice were inoculated intraperitoneally with human ovarian cancer cells (ES-2) and treated with a single intraperitoneal injection of 224Ra-labeled CaCO3 microparticles with varying combinations of mass and activity dose, or cationic 224Ra in solution. Survival and ascites volume at sacrifice were evaluated. RESULTS: Significant therapeutic effect was achieved for all tested specific activities ranging from 0.4 to 4.6 kBq/mg. Although treatment with a mean activity dose of 1305 kBq/kg of cationic 224Ra prolonged the survival compared with the control, equivalent median survival could be achieved with 224Ra-labeled microparticles with a mean dose of only 420 kBq/kg. The best outcome was achieved with the highest specific activities (2.6 and 4.6 kBq/mg). CONCLUSION: Radium-224-labeled CaCO3 microparticles present a promising therapy against cancer dissemination in body cavities.

Use of Immunomodulating Drugs and Risk of Cutaneous Melanoma: A Nationwide Nested Case-Control Study.

PURPOSE: Cutaneous melanoma is among the fastest growing malignancies in Norway and ultraviolet radiation (UVR) exposure is the primary environmental risk factor. Immunomodulating drugs can increase skin photosensitivity and suppress immune responses, and by such mechanisms influence melanoma risk. We, therefore, aimed to examine the associations between use of immunomodulating drugs and melanoma risk, at a nationwide population level. PATIENTS AND METHODS: In the Cancer Registry of Norway, we identified all cases aged 18-85 with a first primary cutaneous melanoma diagnosed in 2007-2015 (n=12,106). These were matched to population controls from the Norwegian National Registry 1:10 (n=118,564), on sex and year of birth using risk set sampling. Information on prescribed drugs (2004-2015) was obtained by linkage to the Norwegian Prescription Database (NorPD). Conditional logistic regression was used to estimate rate ratios (RRs) and 95% confidence intervals (CIs) for associations between use of immunomodulating drugs (immunosuppressants and corticosteroids) and melanoma risk, adjusted for ambient UVR and other drug use. RESULTS: Compared with ≤1 prescription, use of ≥8 prescriptions of immunosuppressants was associated with increased risk of melanoma (RR 1.50, 95% CI 1.27, 1.77). Similar associations were found for subgroups of immunosuppressants: drugs typically prescribed to organ transplant recipients (OTRs) (RR 2.02, 95% CI 1.35, 3.03) and methotrexate (RR 1.27, 95% CI 1.04, 1.55). Similar results were found for high levels of cumulative doses and across all histological subtypes. Use of corticosteroids was not associated with melanoma risk. CONCLUSION: We found a positive association between use of immunosuppressants and melanoma risk, with the highest risk seen for drugs prescribed to OTRs. Knowledge about this risk increase is important for physicians and users of these drugs, for intensified surveillance, awareness and cautious sun exposure.

Calibration of sodium iodide detectors and reentrant ionization chambers for 212Pb activity in different geometries by HPGe activity determined samples.

Lead-212 is a promising radionuclide for cancer therapy, but no primary 212Pb activity standardization has been published. A need therefore exists for accurate estimation of injected doses of 212Pb activity in equilibrium with progeny, when it comes to preclinical and clinical trials. In this study, 212Pb activity was determined using a high purity germanium (HPGe) detector, which allowed the determination of geometry-specific calibration factors for commercially available reentrant ionization chambers (ICs) and sodium iodide (NaI) detectors.

In situ Generated 212Pb-PSMA Ligand in a 224Ra-Solution for Dual Targeting of Prostate Cancer Sclerotic Stroma and PSMA-positive Cells.

BACKGROUND: New treatments combating bone and extraskeletal metastases are needed for patients with metastatic castration-resistant prostate cancer. The majority of metastases overexpress prostate-specific membrane antigen (PSMA), making it an ideal candidate for targeted radionuclide therapy. OBJECTIVE: The aim of this study was to test a novel liquid 224Ra/212Pb-generator for the rapid preparation of a dual-alpha targeting solution. Here, PSMA-targeting ligands are labelled with 212Pb in the 224Ra-solution in transient equilibrium with daughter nuclides. Thus, natural bone-seeking 224Ra targeting sclerotic bone metastases and 212Pb-chelated PSMA ligands targeting PSMA-expressing tumour cells are obtained. METHODS: Two PSMA-targeting ligands, the p-SCN-Bn-TCMC-PSMA ligand (NG001), specifically developed for chelating 212Pb, and the most clinically used DOTA-based PSMA-617 were labelled with 212Pb. Radiolabelling and targeting potential were investigated in situ, in vitro (PSMA-positive C4-2 human prostate cancer cells) and in vivo (athymic mice bearing C4-2 xenografts). RESULTS: NG001 was rapidly labelled with 212Pb (radiochemical purity >94% at concentrations of ≥15 µg/ml) using the liquid 224Ra/212Pb-generator. The high radiochemical purity and stability of [212Pb]Pb- NG001 were demonstrated over 48 hours in the presence of ascorbic acid and albumin. Similar binding abilities of the 212Pb-labelled ligands were observed in C4-2 cells. The PSMA ligands displayed comparable tumour uptake after 2 hours, but NG001 showed a 3.5-fold lower kidney uptake than PSMA- 617. Radium-224 was not chelated and, hence, showed high uptake in bones. CONCLUSION: A fast method for the labelling of PSMA ligands with 212Pb in the 224Ra/212Pb-solution was developed. Thus, further in vivo studies with dual tumour targeting by alpha-particles are warranted.

Photodynamic Efficacy of Cercosporin in 3D Tumor Cell Cultures.

In the present work, we study the photodynamic action of cercosporin (cerco), a naturally occurring photosensitizer, on human cancer multicellular spheroids. U87 spheroids exhibit double the uptake of cerco than T47D and T98G spheroids as shown by flow cytometry on the single cell level. Moreover, cerco is efficiently internalized by cells throughout the spheroid as shown by confocal microscopy, for all three cell lines. Despite their higher cerco uptake, U87 spheroids show the least vulnerability to cerco-PDT, in contrast to the other two cell lines (T47D and T98G). While 300 µm diameter spheroids consistently shrink and become necrotic after cerco PDT, bigger spheroids (>500 µm) start to regrow following blue-light PDT and exhibit high viability. Cerco-PDT was found to be effective on bigger spheroids reaching 1mm in diameter especially under longer exposure to yellow light (~590 nm). In terms of metabolism, T47D and T98G undergo a complete bioenergetic collapse (respiration and glycolysis) as a result of cerco-PDT. U87 spheroids also experienced a respiratory collapse following cerco-PDT, but retained half their glycolytic activity.

Use of Antidepressants and Risk of Cutaneous Melanoma: A Prospective Registry-Based Case-Control Study.

PURPOSE: Melanoma is the cancer with the most rapidly rising incidence rate in Norway. Although exposure to ultraviolet radiation (UVR) is the major environmental risk factor, other factors may also contribute. Antidepressants have cancer inhibiting and promoting side effects, and their prescription rates have increased in parallel with melanoma incidence. Thus, we aimed to prospectively examine the association between use of antidepressants and melanoma by using nation-wide data from the Cancer Registry of Norway, the National Registry, the Norwegian Prescription Database and the Medical Birth Registry of Norway. PATIENT AND METHODS: All cases aged 18-85 with a primary cutaneous invasive melanoma diagnosed during 2007-2015 (n=12,099) were matched to population controls 1:10 (n=118,467) by sex and year of birth using risk-set sampling. We obtained information on prescribed antidepressants and other potentially confounding drug use (2004-2015). Conditional logistic regression was used to estimate adjusted rate ratios (RRs) and 95% confidence intervals (CIs) for the association between overall and class-specific use of antidepressants and incident melanoma. RESULTS: Compared with ≤1 prescription, ≥8 prescriptions of antidepressants overall were negatively associated with melanoma (RR 0.81 CI 0.75-0.87). Class-specific analyses showed decreased RRs for selective serotonin reuptake inhibitors (RR 0.82 CI 0.73-0.93) and mixed antidepressants (RR 0.77 CI 0.69-0.86). The negative association was found for both sexes, age ≥50 years, residential regions with medium and highest ambient UVR exposure, all histological subtypes, trunk, upper and lower limb sites and local disease. CONCLUSION: Use of antidepressants was associated with decreased risk of melanoma. There are at least two possible explanations for our results; cancer-inhibiting actions induced by the drug and less UVR exposure among the most frequent users of antidepressants.

Preparation of the alpha-emitting prostate-specific membrane antigen targeted radioligand [212 Pb]Pb-NG001 for prostate cancer.

Prostate-specific membrane antigen (PSMA) is the most promising target for radioligand therapy of prostate cancer. The aim of this study was to prepare a small molecular ligand p-SCN-Bn-TCMC-PSMA (NG001) and compare it with the commonly used DOTA-based PSMA-617. The PSMA-targeting ability of the 212 Pb-labelled ligands was evaluated using PSMA-positive C4-2 human prostate cancer cells. Lead-212 is an in vivo generator of alpha particles by its daughter nuclides 212 Bi and 212 Po. NG001 was synthesized by conjugating the isothiocyanato group of p-SCN-Bn-TCMC to the amino group of a glutamate-urea-based PSMA-binding entity. Molecular size, chelator unit and chelator linking method are different in NG001 and PSMA-617. Both ligands were efficiently labelled with 212 Pb using a 224 Ra/212 Pb-solution generator in transient equilibrium with progeny. Lead-212-labelled NG001 was purified with a yield of 85.9±4.7% and with 0.7±0.2% of 224 Ra. Compared with [212 Pb]Pb-PSMA-617, [212 Pb]Pb-NG001 displayed a similar binding and internalization in C4-2 cells, with comparable tumour uptake in mice bearing C4-2 tumours, but almost a 2.5-fold lower kidney uptake. Due to the rapid normal tissue clearance and tumour cell internalization, any significant translocalization of 212 Bi was not detected in mice. In conclusion, the obtained results warrant further preclinical studies to evaluate the therapeutic efficacy of [212 Pb]Pb-NG001.

Cardiovascular, antidepressant and immunosuppressive drug use in relation to risk of cutaneous melanoma: a protocol for a prospective case-control study.

INTRODUCTION: The incidence of cutaneous melanoma (hereafter melanoma) has increased dramatically among fair-skinned populations worldwide. In Norway, melanoma is the most rapidly growing type of cancer, with a 47% increase among women and 57% among men in 2000-2016. Intermittent ultraviolet exposure early in life and phenotypic characteristics like a fair complexion, freckles and nevi are established risk factors, yet the aetiology of melanoma is multifactorial. Certain prescription drugs may have carcinogenic side effects on the risk of melanoma. Some cardiovascular, antidepressant and immunosuppressive drugs can influence certain biological processes that modulate photosensitivity and immunoregulation. We aim to study whether these drugs are related to melanoma risk. METHODS AND ANALYSIS: A population-based matched case-control study will be conducted using nation-wide registry data. Cases will consist of all first primary, histologically verified melanoma cases diagnosed between 2007 and 2015 identified in the Cancer Registry of Norway (14 000 cases). Ten melanoma-free controls per case (on date of case melanoma diagnosis) will be matched based on sex and year of birth from the National Registry of Norway. For the period 2004-2015, and by using the unique personal identification numbers assigned to all Norwegian citizens, the case-control data set will be linked to the Norwegian Prescription Database for information on drugs dispensed prior to the melanoma diagnosis, and to the Medical Birth Registry of Norway for data regarding the number of child births. Conditional logistic regression will be used to estimate associations between drug use and melanoma risk, taking potential confounding factors into account. ETHICS AND DISSEMINATION: The project is approved by the Regional Committee for Medical Research Ethics in Norway and by the Norwegian Data Protection Authority. The study is funded by the Southeastern Norway Regional Health Authority. Results will be published in peer-reviewed journals and disseminated further through scientific conferences, news media and relevant patient interest groups.

Antitumor Activity of Novel Bone-seeking, α-emitting 224Ra-solution in a Breast Cancer Skeletal Metastases Model.

BACKGROUND/AIM: Bone metastases are associated with increased morbidity and poor prognosis in a variety of cancers. The present study investigated the effects of targeted radionuclide therapy with α-emitting, bone-seeking radium-224 (224Ra) on osteolytic bone metastasis of MDA-MB-231(SA)-GFP human breast cancer cells injected intracardially into nude mice. MATERIALS AND METHODS: Vehicle, ethylenediamine tetra (methylene phosphonic acid) (EDTMP) and 224Ra-solution (45, 91 or 179 kBq/kg) with EDTMP were intravenously administered to mice two days after cell injection. The bone-seeking EDTMP was added to the 224Ra-solution to improve bone targeting of 212Pb, which is a progeny of 224Ra. RESULTS: Radium-224 solution treatment decreased in a dose-dependent manner the areas of osteolytic lesions in the hind limbs and the number of tumor foci in the whole skeleton, and extended survival. Paraplegia was not observed in 179 kBq/kg 224Ra-solution group. CONCLUSION: Radium-224-solution containing chelated 212Pb is a promising candidate for the treatment of breast cancer patients with bone metastases.