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Dual targeting with 224Ra/ 212Pb-conjugates for targeted alpha therapy of disseminated cancers: A conceptual approach. Front Med (Lausanne) 2023; 9:1051825. [PMID: 36733936 PMCID: PMC9887039 DOI: 10.3389/fmed.2022.1051825] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 12/05/2022] [Indexed: 01/18/2023] Open
Abstract
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.
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Comparing absorbed doses and radiation risk of the α-emitting bone-seekers [ 223Ra]RaCl 2 and [ 224Ra]RaCl 2. Front Med (Lausanne) 2023; 9:1057373. [PMID: 36687439 PMCID: PMC9847387 DOI: 10.3389/fmed.2022.1057373] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 12/05/2022] [Indexed: 01/05/2023] Open
Abstract
[223Ra]RaCl2 and [224Ra]RaCl2 are bone seekers, emitting high LET, and short range (< 100 μm) alpha-particles. Both radionuclides show similar decay properties; the total alpha energies are comparable (223Ra: ≈28 MeV, 224Ra: ≈26 MeV). [224Ra]RaCl2 has been used from the mid-1940s until 1990 for treating different bone and joint diseases with activities of up to approximately 50 MBq [224Ra]RaCl2. In 2013 [223Ra]RaCl2 obtained marketing authorization by the FDA and by the European Union for the treatment of metastatic prostate cancer with an activity to administer of 0.055 MBq per kg body weight for six cycles. For intravenous injections in humans a model calculation using the biokinetic model of ICRP67 shows a ratio of organ absorbed dose coefficients (224Ra:223Ra) between 0.37 (liver) and 0.97 except for the kidneys (2.27) and blood (1.57). For the red marrow as primary organ-at-risk, the ratio is 0.57. The differences are mainly caused be the differing half-lives of the decay products of both radium isotopes. Both radionuclides show comparable DNA damage patterns in peripheral blood mononuclear cells after internal ex-vivo irradiation. Data on the long-term radiation-associated side effects are only available for treatment with [224Ra]RaCl2. Two epidemiological studies followed two patient groups treated with [224Ra]RaCl2 for more than 25 years. One of them was the "Spiess study", a cohort of 899 juvenile patients who received several injections of [224Ra]RaCl2 with a mean specific activity of 0.66 MBq/kg. Another patient group of ankylosing spondylitis patients was treated with 10 repeated intravenous injections of [224Ra]RaCl2, 1 MBq each, 1 week apart. In total 1,471 of these patients were followed-up in the "Wick study". In both studies, an increased cancer mortality by leukemia and solid cancers was observed. Similar considerations on long-term effects likely apply to [223Ra]RaCl2 as well since the biokinetics are similar and the absorbed doses in the same range. However, this increased risk will most likely not be observed due to the much shorter life expectancy of prostate cancer patients treated with [223Ra]RaCl2.
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Estimating the Risk for Secondary Cancer After Targeted α-Therapy with 211At Intraperitoneal Radioimmunotherapy. J Nucl Med 2023; 64:165-172. [PMID: 35798559 PMCID: PMC9841246 DOI: 10.2967/jnumed.121.263349] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 06/02/2022] [Accepted: 06/02/2022] [Indexed: 01/28/2023] Open
Abstract
Intraperitoneal 211At-based targeted α-therapy (TAT) may hold great promise as an adjuvant therapy after surgery and chemotherapy in epithelial ovarian cancer to eradicate any remaining undetectable disease. This implies that it will also be delivered to patients possibly already cured by the primary treatment. An estimate of long-term risks is therefore sought to determine whether the treatment is justified. Methods: Baseline data for risk estimates of α-particle irradiation were collected from published studies on excess cancer induction and mortality for subjects exposed to either 224Ra treatments or Thorotrast contrast agent (25% ThO2 colloid, containing 232Th). Organ dosimetry for 224Ra and Thorotrast irradiation were taken from the literature. These organ-specific risks were then applied to our previously reported dosimetry for intraperitoneal 211At-TAT patients. Results: Risk could be estimated for 10 different organ or organ groups. The calculated excess relative risk per gray (ERR/Gy) could be sorted into 2 groups. The lower-ERR/Gy group, ranging up to a value of approximately 5, included trachea, bronchus, and lung, at 0.52 (95% CI, 0.21-0.82); stomach, at 1.4 (95% CI, -5.0-7.9); lymphoid and hematopoietic system, at 2.17 (95% CI, 1.7-2.7); bone and articular cartilage, at 2.6 (95% CI, 2.0-3.3); breast, at 3.45 (95% CI, -10-17); and colon, at 4.5 (95% CI, -3.5-13). The higher-ERR/Gy group, ranging from approximately 10 to 15, included urinary bladder, at 10.1 (95% CI, 1.4-23); liver, at 14.2 (95% CI, 13-16); kidney, at 14.9 (95% CI, 3.9-26); and lip, oral cavity, and pharynx, at 15.20 (95% CI, 2.73-27.63). Applying a typical candidate patient (female, age 65 y) and correcting for the reference population mortality rate, the total estimated excess mortality for an intraperitoneal 211At-monoclonal antibody treatment amounted to 1.13 per 100 treated. More than half this excess originated from urinary bladder and kidney, 0.29 and 0.34, respectively. Depending on various adjustments in calculation and assumptions on competing risks, excess mortality could range from 0.11 to 1.84 per 100 treated. Conclusion: Published epidemiologic data on lifelong detriment after α-particle irradiation and its dosimetry allowed calculations to estimate the risk for secondary cancer after 211At-based intraperitoneal TAT. Measures to reduce dose to the urinary organs may further decrease the estimated relative low risk for secondary cancer from 211At-monoclonal antibody-based intraperitoneal TAT.
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Radiopharmaceutical Quality Control Considerations for Accelerator-Produced Actinium Therapies. Cancer Biother Radiopharm 2022; 37:355-363. [PMID: 35695807 PMCID: PMC9242709 DOI: 10.1089/cbr.2022.0010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Background: Alpha-particle-emitting radiotherapies are of great interest for the treatment of disseminated cancer. Actinium-225 (225Ac) produces four α-particles through its decay and is among the most attractive radionuclides for use in targeted radiotherapy applications. However, supply issues for this isotope have limited availability and increased cost for research and translation. Efforts have focused on accelerator-based methods that produce 225Ac in addition to long-lived 227Ac. Objective: The authors investigated the impact of 225Ac/227Ac material in the radiolabeling and radiopharmaceutical quality control evaluation of a DOTA chelate-conjugated peptide under good manufacturing practices. The authors use an automated module under identical conditions with either generator or accelerator-produced actinium radiolabeling. Methods: The authors have performed characterization of the radiolabeled products, including thin-layer chromatography, high-pressure liquid chromatography, gamma counting, and high-energy resolution gamma spectroscopy. Results: Peptide was radiolabeled and assessed at >95% radiochemical purity with high yields for generator produced 225Ac. The radiolabeling results produced material with subtle but detectable differences when using 225Ac/227Ac. Gamma spectroscopy was able to identify peptide initially labeled with 227Th, and at 100 d for quantification of 225Ac-bearing peptide. Conclusion: Peptides produced using 225Ac/227Ac material may be suitable for translation, but raise new issues that include processing times, logistics, and contaminant detection.
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Improving Theranostic Gallium-68/Lutetium-177-Labeled PSMA Inhibitors with an Albumin Binder for Prostate Cancer. Mol Cancer Ther 2021; 20:2410-2419. [PMID: 34725194 DOI: 10.1158/1535-7163.mct-21-0251] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 07/21/2021] [Accepted: 09/29/2021] [Indexed: 11/16/2022]
Abstract
We developed a novel therapeutic radioligand, [177Lu]1h, with an albumin binding motif and evaluated it in a prostate-specific membrane antigen (PSMA)-expressing tumor xenograft mouse model. Fourteen PSMA target candidates were synthesized, and binding affinity was evaluated with an in vitro competitive binding assay. First, four compound candidates were selected depending on binding affinity results. Next, we selected four compounds ([68Ga]1e, [68Ga]1g, [68Ga]1h, and [68Ga]1k) were screened for tumor targeting efficiency by micro-positron emission tomography/computed tomography (micro-PET/CT) imaging. Finally, [177Lu]1h compound was evaluated the tumor targeting efficiency and therapeutic efficiency by micro-single-photon emission computed tomography/computed tomography (micro-SPECT/CT), biodistribution, and radiotherapy studies. Estimated human effective dose was calculated by biodistribution data. Compound 1h showed a high binding affinity (Ki value = 4.08 ± 0.08 nmol/L), and [177Lu]1h showed extended blood circulation (1 hour = 10.32 ± 0.31, 6 hours = 2.68 ± 1.07%ID/g) compared to [177Lu]PSMA-617 (1 h = 0.17 ± 0.10%ID/g). [177Lu]1h was excreted via the renal pathway and showed high tumor uptake (24.43 ± 3.36%ID/g) after 1 hour, which increased over 72 hours (72 hours = 51.39 ± 9.26%ID/g). Mice treated with 4 and 6 MBq of [177Lu]1h showed a median survival rate of >61 days. In particular, all mice treated with 6 MBq of [177Lu]1h survived for the entire monitoring period. The estimated human effective dose of [177Lu]1h was 0.07 ± 0.01 and 0.03 ± 0.00 mSv/MBq in total body and kidney, respectively. The current study indicates that [177Lu]1h has the potential for further investigation of metastatic castration-resistant prostate cancer (mCRPC) therapy in clinical trials.
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In situ Generated <sup>212</sup>Pb-PSMA Ligand in a <sup>224</sup>Ra-Solution for Dual Targeting of Prostate Cancer Sclerotic Stroma and PSMA-positive Cells. Curr Radiopharm 2021; 13:130-141. [PMID: 32389119 PMCID: PMC7527546 DOI: 10.2174/1874471013666200511000532] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 02/18/2020] [Accepted: 02/23/2020] [Indexed: 12/31/2022]
Abstract
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.
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Administration of lower doses of radium-224 to ankylosing spondylitis patients results in no evidence of significant overall detriment. PLoS One 2020; 15:e0232597. [PMID: 32353063 PMCID: PMC7192484 DOI: 10.1371/journal.pone.0232597] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Accepted: 04/17/2020] [Indexed: 12/02/2022] Open
Abstract
The use of low doses of radium-224 (224Ra) chloride for the treatment of ankylosing spondylitis was stopped following the discovery that patients treated with it had a higher than control incidence of leukaemia and other cancers. This was so even though the treatment resulted in decreased pain and increased mobility-both of which are associated with decreased mortality. It was decided to re-analyze the epidemiological data looking at all causes of death. The risk of leukaemia, solid cancer, death from non-cancer causes and from all causes in a study populations of men that received either the typical dose of 5.6 to 11.1 MBq of 224Ra, any dose of 224Ra or no radium were compared using the Cox proportional hazard model. For patients that received the typical dose of 224Ra agreed with the excess cancer was similar to that reported in previous studies. In contrast, these patients were less likely to die from non-cancer diseases and from all causes of death than the control patients. No excess mortality was also found in the population of all males that received the radionuclide. It is concluded that 224Ra treatment administered at low doses to patients with ankylosing spondylitis did not impact mortality from all causes. The study demonstrates the need to consider all causes of death and longevity when assessing health impacts following irradiation.
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Atomic Nanogenerators in Targeted Alpha Therapies: Curie's Legacy in Modern Cancer Management. Pharmaceuticals (Basel) 2020; 13:ph13040076. [PMID: 32340103 PMCID: PMC7243103 DOI: 10.3390/ph13040076] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 04/17/2020] [Accepted: 04/21/2020] [Indexed: 12/12/2022] Open
Abstract
Atomic in vivo nanogenerators such as actinium-225, thorium-227, and radium-223 are of increasing interest and importance in the treatment of patients with metastatic cancer diseases. This is due to their peculiar physical, chemical, and biological characteristics, leading to astonishing responses in otherwise resistant patients. Nevertheless, there are still a few obstacles and hurdles to be overcome that hamper the broader utilization in the clinical setting. Next to the limited supply and relatively high costs, the in vivo complex stability and the fate of the recoiling daughter radionuclides are substantial problems that need to be solved. In radiobiology, the mechanisms underlying treatment efficiency, possible resistance mechanisms, and late side effect occurrence are still far from being understood and need to be unraveled. In this review, the current knowledge on the scientific and clinical background of targeted alpha therapies is summarized. Furthermore, open issues and novel approaches with a focus on the future perspective are discussed. Once these are unraveled, targeted alpha therapies with atomic in vivo nanogenerators can be tailored to suit the needs of each patient when applying careful risk stratification and combination therapies. They have the potential to become one of the major treatment pillars in modern cancer management.
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Preparation of the alpha-emitting prostate-specific membrane antigen targeted radioligand [ 212 Pb]Pb-NG001 for prostate cancer. J Labelled Comp Radiopharm 2020; 63:129-143. [PMID: 31919866 DOI: 10.1002/jlcr.3825] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 12/17/2019] [Accepted: 01/06/2020] [Indexed: 12/26/2022]
Abstract
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.
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Correlation of the absorbed dose to the blood and DNA damage in leukocytes after internal ex-vivo irradiation of blood samples with Ra-224. EJNMMI Res 2018; 8:77. [PMID: 30083998 PMCID: PMC6082247 DOI: 10.1186/s13550-018-0422-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 07/06/2018] [Indexed: 01/04/2023] Open
Abstract
Background Irradiation with α-particles creates densely packed damage tracks along particle trajectories in exposed cells, including complex DNA damage and closely spaced double-strand breaks (DSBs) in hit nuclei. Here, we investigated the correlation of the absorbed dose to the blood and the number of α-induced DNA damage tracks elicited in human blood leukocytes after ex-vivo in-solution exposure with Ra-224. The aim was to compare the data to previously published data on Ra-223 and to investigate differences in DNA damage induction between the two radium isotopes. Results Blood samples from three healthy volunteers were exposed ex-vivo to six different concentrations of Ra-224 dichloride. Absorbed doses to the blood were calculated assuming local energy deposition of all α- and β-particles of the Ra-224 decay chain, ranging from 0 to 127 mGy. γ-H2AX + 53BP1 DNA damage co-staining and analysis was performed on ethanol-fixed leukocytes isolated from the irradiated blood samples. For damage quantification, α-induced DNA damage tracks and small γ-H2AX + 53BP1 DSB foci were enumerated in the exposed leukocytes. This revealed a linear relationship between the frequency of α-induced γ-H2AX damage tracks and the absorbed dose to the blood, while the frequency of small γ-H2AX + 53BP1 DSB foci indicative of β-irradiation was similar to baseline values. Conclusions Our data provide a first estimation of the DNA damage induced by Ra-224 in peripheral blood mononuclear cells. A comparison with our previously published Ra-223 data suggests that there is no difference in the induction of radiation-induced DNA damage between the two radium isotopes due to their similar decay properties.
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Abstract
α-Particle irradiation of cancerous tissue is increasingly recognized as a potent therapeutic option. We briefly review the physics, radiobiology, and dosimetry of α-particle emitters, as well as the distinguishing features that make them unique for radiopharmaceutical therapy. We also review the emerging clinical role of α-particle therapy in managing cancer and recent studies on in vitro and preclinical α-particle therapy delivered by antibodies, other small molecules, and nanometer-sized particles. In addition to their unique radiopharmaceutical characteristics, the increased availability and improved radiochemistry of α-particle radionuclides have contributed to the growing recent interest in α-particle radiotherapy. Targeted therapy strategies have presented novel possibilities for the use of α-particles in the treatment of cancer. Clinical experience has already demonstrated the safe and effective use of α-particle emitters as potent tumor-selective drugs for the treatment of leukemia and metastatic disease.
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New physical approaches to treat cancer stem cells: a review. Clin Transl Oncol 2018; 20:1502-1521. [PMID: 29869042 DOI: 10.1007/s12094-018-1896-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 05/14/2018] [Indexed: 12/13/2022]
Abstract
Cancer stem cells (CSCs) have been identified as the main center of tumor therapeutic resistance. They are highly resistant against current cancer therapy approaches particularly radiation therapy (RT). Recently, a wide spectrum of physical methods has been proposed to treat CSCs, including high energetic particles, hyperthermia (HT), nanoparticles (NPs) and combination of these approaches. In this review article, the importance and benefits of the physical CSCs therapy methods such as nanomaterial-based heat treatments and particle therapy will be highlighted.
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Application of astatine-210: Evaluation of astatine distribution and effect of pre-injected iodide in whole body of normal rats. Appl Radiat Isot 2018; 139:251-255. [PMID: 29870920 DOI: 10.1016/j.apradiso.2018.05.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 04/23/2018] [Accepted: 05/22/2018] [Indexed: 12/16/2022]
Abstract
We proposed use of astatine-210 in preclinical study. Astatine-210 has higher yield of production and is easier to quantify than astatine-211. We produced astatine-210 with Bi target and 40 MeV alpha beam accelerated by cyclotron, free astatine-210 was separated and injected to normal rats. Three male rats (blocking group) were injected non-radioactive iodide before injection of astatine-210. Compared with the control group, the astatine-210 accumulations in the blocking group decreased to 24% in the thyroid.
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Preparation of 212Pb-labeled monoclonal antibody using a novel 224Ra-based generator solution. Nucl Med Biol 2017; 51:1-9. [PMID: 28486098 DOI: 10.1016/j.nucmedbio.2017.04.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 04/06/2017] [Accepted: 04/15/2017] [Indexed: 12/16/2022]
Abstract
INTRODUCTION Alpha-emitting radionuclides have gained considerable attention as payloads for cancer targeting molecules due to their high cytotoxicity. One attractive radionuclide for this purpose is 212Pb, which by itself is a β-emitter, but acts as an in vivo generator for its short-lived α-emitting daughters. The standard method of preparing 212Pb-labeled antibodies requires handling and evaporation of strong acids containing high radioactivity levels by the end user. An operationally easier and more rapid process could be useful since the 10.6h half-life of 212Pb puts time constraints on the preparation protocol. In this study, an in situ procedure for antibody labeling with 212Pb, using a solution of the generator nuclide 224Ra, is proposed as an alternative protocol for preparing 212Pb-radioimmunoconjugates. METHODS Radium-224, the generator radionuclide of 212Pb, was extracted from its parent nuclide, 228Th. Lead-212-labeling of the TCMC-chelator conjugated monoclonal antibody trastuzumab was carried out in a solution containing 224Ra in equilibrium with progeny. Subsequently, the efficiency of separating the 212Pb-radioimmunoconjugate from 224Ra and other unconjugated daughter nuclides in the solution using either centrifugal separation or a PD-10 desalting size exclusion column was evaluated and compared. RESULTS Radiolabeling with 212Pb in 224Ra-solutions was more than 90% efficient after only 30min reaction time at TCMC-trastuzumab concentrations from 0.15mg/mL and higher. Separation of 212Pb-labeled trastuzumab from 224Ra using a PD-10 column was clearly superior to centrifugal separation. This method allowed recovery of approximately 75% of the 212Pb-antibody-conjugate in the eluate, and the remaining amount of 224Ra was only 0.9±0.8% (n=7). CONCLUSIONS The current work demonstrates a novel method of producing 212Pb-based radioimmunoconjugates from a 224Ra-solution, which may be simpler and less time-consuming for the end user compared with the method established for use in clinical trials of 212Pb-TCMC-trastuzumab.
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Absorbed Doses and Risk Estimates of (211)At-MX35 F(ab')2 in Intraperitoneal Therapy of Ovarian Cancer Patients. Int J Radiat Oncol Biol Phys 2015; 93:569-76. [PMID: 26460999 DOI: 10.1016/j.ijrobp.2015.07.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 06/22/2015] [Accepted: 07/06/2015] [Indexed: 11/29/2022]
Abstract
PURPOSE Ovarian cancer is often diagnosed at an advanced stage with dissemination in the peritoneal cavity. Most patients achieve clinical remission after surgery and chemotherapy, but approximately 70% eventually experience recurrence, usually in the peritoneal cavity. To prevent recurrence, intraperitoneal (i.p.) targeted α therapy has been proposed as an adjuvant treatment for minimal residual disease after successful primary treatment. In the present study, we calculated absorbed and relative biological effect (RBE)-weighted (equivalent) doses in relevant normal tissues and estimated the effective dose associated with i.p. administration of (211)At-MX35 F(ab')2. METHODS AND MATERIALS Patients in clinical remission after salvage chemotherapy for peritoneal recurrence of ovarian cancer underwent i.p. infusion of (211)At-MX35 F(ab')2. Potassium perchlorate was given to block unwanted accumulation of (211)At in thyroid and other NIS-containing tissues. Mean absorbed doses to normal tissues were calculated from clinical data, including blood and i.p. fluid samples, urine, γ-camera images, and single-photon emission computed tomography/computed tomography images. Extrapolation of preclinical biodistribution data combined with clinical blood activity data allowed us to estimate absorbed doses in additional tissues. The equivalent dose was calculated using an RBE of 5 and the effective dose using the recommended weight factor of 20. All doses were normalized to the initial activity concentration of the infused therapy solution. RESULTS The urinary bladder, thyroid, and kidneys (1.9, 1.8, and 1.7 mGy per MBq/L) received the 3 highest estimated absorbed doses. When the tissue-weighting factors were applied, the largest contributors to the effective dose were the lungs, stomach, and urinary bladder. Using 100 MBq/L, organ equivalent doses were less than 10% of the estimated tolerance dose. CONCLUSION Intraperitoneal (211)At-MX35 F(ab')2 treatment is potentially a well-tolerated therapy for locally confined microscopic ovarian cancer. Absorbed doses to normal organs are low, but because the effective dose potentially corresponds to a risk of treatment-induced carcinogenesis, optimization may still be valuable.
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A Critical Review of Alpha Radionuclide Therapy-How to Deal with Recoiling Daughters? Pharmaceuticals (Basel) 2015; 8:321-36. [PMID: 26066613 PMCID: PMC4491664 DOI: 10.3390/ph8020321] [Citation(s) in RCA: 123] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 05/19/2015] [Accepted: 06/01/2015] [Indexed: 01/20/2023] Open
Abstract
This review presents an overview of the successes and challenges currently faced in alpha radionuclide therapy. Alpha particles have an advantage in killing tumour cells as compared to beta or gamma radiation due to their short penetration depth and high linear energy transfer (LET). Touching briefly on the clinical successes of radionuclides emitting only one alpha particle, the main focus of this article lies on those alpha-emitting radionuclides with multiple alpha-emitting daughters in their decay chain. While having the advantage of longer half-lives, the recoiled daughters of radionuclides like 224Ra (radium), 223Ra, and 225Ac (actinium) can do significant damage to healthy tissue when not retained at the tumour site. Three different approaches to deal with this problem are discussed: encapsulation in a nano-carrier, fast uptake of the alpha emitting radionuclides in tumour cells, and local administration. Each approach has been shown to have its advantages and disadvantages, but when larger activities need to be used clinically, nano-carriers appear to be the most promising solution for reducing toxic effects, provided there is no accumulation in healthy tissue.
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Dosimetry of 223Ra-chloride: dose to normal organs and tissues. Eur J Nucl Med Mol Imaging 2012; 40:207-12. [PMID: 23053328 DOI: 10.1007/s00259-012-2265-y] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 09/25/2012] [Indexed: 02/08/2023]
Abstract
PURPOSE (223)Ra-Chloride (also called Alpharadin®) targets bone metastases with short range alpha particles. In recent years several clinical trials have been carried out showing, in particular, the safety and efficacy of palliation of painful bone metastases in patients with castration-resistant prostate cancer using (223)Ra-chloride. The purpose of this work was to provide a comprehensive dosimetric calculation of organ doses after intravenous administration of (223)Ra-chloride according to the present International Commission on Radiological Protection (ICRP) model for radium. METHODS Absorbed doses were calculated for 25 organs or tissues. RESULTS Bone endosteum and red bone marrow show the highest dose coefficients followed by liver, colon and intestines. After a treatment schedule of six intravenous injections with 0.05 MBq/kg of (223)Ra-chloride each, corresponding to 21 MBq for a 70 kg patient, the absorbed alpha dose to the bone endosteal cells is about 16 Gy and the corresponding absorbed dose to the red bone marrow is approximately 1.5 Gy. CONCLUSION The comprehensive list of dose coefficients presented in this work will assist in comparing and evaluating organ doses from various therapy modalities used in nuclear medicine and will provide a base for further development of patient-specific dosimetry.
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Growth retardation and destruction of experimental squamous cell carcinoma by interstitial radioactive wires releasing diffusing alpha-emitting atoms. Int J Cancer 2007; 122:1657-64. [DOI: 10.1002/ijc.23268] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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[Effectiveness and safety of radium chloride in the treatment of ankylosing spondylitis. Results of an observational study]. Z Rheumatol 2007; 65:245-51. [PMID: 16477453 DOI: 10.1007/s00393-005-0009-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2004] [Accepted: 07/14/2005] [Indexed: 01/06/2023]
Abstract
After radium chloride was approved for the therapy of ankylosing spondylitis (AS) in Germany on October 23, 2000, an open, non-comparative prospective observational study was planed. The assessment involved 308 patients with the diagnosis of AS and radiological evidence of spinal involvement who were treated with at least one injection of radium chloride. 278 of these patients received the full cycle of 10 injections (a total of 10 MBq radium-224) one injection one per week for a period of 10 successive weeks. Validated outcomes were measured before therapy and six months after therapy according to the recommendations of the "assessment in ankylosing spondylitis working group"(ASAS). The primary endpoint was disease activity assessed using the BASDAI ("Bath Ankylosing Spondylitis Disease Activity Index"). Secondary endpoints included the BASFI ("Bath Ankylosing Spondylitis Functional Index"), as well as self-reported pain and global patient ratings. Patients showed significant improvement in all of the parameters assessed (BASDAI, BASFI, pain, global patient rating) at 6-months post-treatment. At this time, the mean BASDAI and BASFI scores improved from 5.5 to 3.5 and from 5.6 to 3.7, respectively. Pain decreased from a mean of 7.3 to 4.1, and disease activity (as rated by patients) also decreased from 7.2 to 4.1 (p < 0.001 for all of them). Drug tolerance was good. Six adverse events were documented, none of which was serious and none led to discontinuation of treatment. According to the data provided here medical treatment with radium chloride seems to be effective and safe during an observation period of 6 months. Nevertheless, a randomized placebo-controlled study should be performed in the near future in order to safeguard the level of evidence.
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Abstract
PURPOSE The main goals were to study the safety and tolerability of the alpha-emitter radium-223 (223Ra) in breast and prostate cancer patients with skeletal metastases. In addition, pain palliation was evaluated. EXPERIMENTAL DESIGN Fifteen prostate and 10 breast cancer patients enrolled in a phase I trial received a single i.v. injection of 223Ra. Five patients were included at each of the dosages: 46, 93, 163, 213, or 250 kBq/kg and followed for 8 weeks. Palliative response was evaluated according to the pain scale of the European Organization for Research and Treatment of Cancer QLQ C30 questionnaire at baseline and at 1, 4, and 8 weeks after injection. RESULTS Weekly blood sampling during follow-up revealed mild and reversible myelosuppression with nadir 2 to 4 weeks after the injection. Importantly, for thrombocytes only grade 1 toxicity was reported. Grade 3 neutropenia and leucopenia occurred in two and three patients, respectively. Mild, transient diarrhea was observed in 10 of the 25 patients. Nausea and vomiting was more frequently observed in the highest dosage group. Serum alkaline phosphatase decreased with nadir averages of 29.5% in females and 52.1% in males. Pain relief was reported by 52%, 60%, and 56% of the patients after 7 days, 4, and 8 weeks, respectively. 223Ra cleared rapidly from blood and was below 1% of initial level at 24 hours. Gamma camera images indicated, in accordance with pretreatment (99m)Tc-MDP scans, accumulation of 223Ra in skeletal lesions. Elimination was mainly intestinal. Median survival exceeded 20 months. CONCLUSIONS 223Ra was well tolerated at therapeutically relevant dosages. Phase II studies have therefore been initiated.
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Chromosomal aberrations in peripheral lymphocytes of patients treated with radium-224 for ankylosing spondylitis. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2005; 44:23-28. [PMID: 15818481 DOI: 10.1007/s00411-005-0275-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Accepted: 02/03/2005] [Indexed: 05/24/2023]
Abstract
The aim of this study was to investigate the in vivo frequency of chromosomal aberrations (primarily dicentric chromosomes and chromatid breaks) potentially induced by (224)Ra alpha-radiation in peripheral lymphocytes. The study was designed to serve as a cytogenetic analysis along with the therapeutic procedure of ankylosing spondylitis patients who were undergoing a treatment with (224)Ra-chloride. The total administered activity was 10 MBq, and the treatment followed a schedule of 10 i.v. injections per week, each with a dose of 1 MBq of (224)Ra. The calculation of absorbed doses delivered to the blood used the models suggested by the ICRP and yielded a value of 4.7 mGy/MBq. The frequency of chromosomal aberrations observed during the course of therapy was related to the blood dose. The frequency of dicentric chromosomes induced in vivo was found to agree well with the corresponding value of dicentrics induced in vitro. However--given that peripheral lymphocytes are in the cell cycle's G(0) stage--an unexpected increase with dose in the yield of chromatid breaks was observed, with about 95% of them occurring in cells without any other chromosome-type aberrations. Reasons for the production of chromatid breaks are discussed.
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Bone cancer risk in mice exposed to 224Ra: protraction effects from promotion. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2005; 44:61-7. [PMID: 15864614 DOI: 10.1007/s00411-005-0278-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Accepted: 02/24/2005] [Indexed: 05/02/2023]
Abstract
This paper analyzes data for the osteosarcoma incidence in life-time experiments of (224)Ra injected mice with respect to the importance of initiating and promoting action of ionizing high LET-radiation. This was done with the biologically motivated two step clonal expansion (TSCE) model of tumor induction. Experimentally derived osteosarcoma incidence in 1,194 mice following exposure to (224)Ra with different total radiation doses and different fractionation patterns were analyzed together with incidence data from 1,710 unirradiated control animals. Effects of radiation on the initiating event and on the clonal expansion rate, i.e. on promotion were found to be necessary to explain the observed patterns with this model. The data show a distinct inverse protraction effect at high doses, whereas at lower doses this effect becomes insignificant. Such a behavior is well reproduced in the proposed model: At dose rates above 6 mGy/day a longer exposure produces higher ERR per dose, while for lower rates the reverse is the case. The TSCE model permits the deduction of several kinetic parameters of a postulated two-step bone tumorigenesis process. Mean exposure rates of 0.13 mGy/day are found to double the baseline initiation rate. At rates above 100 mGy/day, the initiation rate decreases. The clonal expansion rate is doubled at 8 mGy/day, and it levels out at rates beyond 100 mGy/day.
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In regard to letter by Muscoplat et al.: Radiation therapy for inflammatory arthritis (Int J Radiat Oncol Biol Phys 2004;60:688–689). Int J Radiat Oncol Biol Phys 2005; 61:961. [PMID: 15708281 DOI: 10.1016/j.ijrobp.2004.11.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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