| 1. |
- Albertsson, Per, 1964, et al.
(författare)
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Astatine-211 based radionuclide therapy: Current clinical trial landscape
- 2023
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Ingår i: Frontiers in Medicine. - : Frontiers Media SA. - 2296-858X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Astatine-211 (At-211) has physical properties that make it one of the top candidates for use as a radiation source for alpha particle-based radionuclide therapy, also referred to as targeted alpha therapy (TAT). Here, we summarize the main results of the completed clinical trials, further describe ongoing trials, and discuss future prospects.
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| 2. |
- Bäck, Tom, 1964, et al.
(författare)
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A Novel Method for Real-Time Quantification of Radioligand Binding to Living Tumor Cells In Vitro
- 2024
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Ingår i: CANCER BIOTHERAPY AND RADIOPHARMACEUTICALS. - 1084-9785 .- 1557-8852. ; 39:1, s. 75-81
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Tidskriftsartikel (refereegranskat)abstract
- Background: Real-time quantification of radioligand binding to cells under in vivo-like conditions improves evaluation of clinical potential.Materials and Methods: SKOV-3 tumor cells were grown in a monolayer on a thin glass plate placed in a sealable shallow chamber with a continuous flow of 125I-trastuzumab solution. The time-dependent cell binding was measured using a NaI detector, and the binding parameters were derived by computational analysis.Results: The detection efficiency of 125I was 65 cps/kBq for radioligand bound to the cells. Experiments were analyzed to find the values of kon and koff. The resulting kon was 3.2-7.9 x 10(4) M-1 s(-1) and koff was 0.11-4.2 x 10(-5) s(-1).Conclusions: Radioligands can be rapidly evaluated by binding to living cells for selection and optimization of radioconjugates for diagnostic and therapeutic purposes.
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| 3. |
- Bäck, Tom, 1964, et al.
(författare)
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Targeted alpha therapy with astatine-211-labeled anti-PSCA A11 minibody shows antitumor efficacy in prostate cancer xenografts and bone microtumors
- 2020
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Ingår i: Ejnmmi Research. - : Springer Science and Business Media LLC. - 2191-219X. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Purpose Targeted alpha therapy (TAT) is a promising treatment for micrometastatic and minimal residual cancer. We evaluated systemic alpha-radioimmunotherapy (alpha-RIT) of metastatic castration-resistant prostate cancer (mCRPC) using the alpha-particle emitter At-211-labeled to the anti-PSCA A11 minibody. A11 is specific for prostate stem cell antigen (PSCA), a cell surface glycoprotein which is overexpressed in more than 90% of both localized prostate cancer and bone metastases. Methods PC3-PSCA cells were implanted subcutaneously (s.c.) and intratibially (i.t) in nude mice. Efficacy of alpha-RIT (two fractions-14-day interval) was studied on s.c. macrotumors (0, 1.5 and 1.9 MBq) and on i.t. microtumors (100-200 mu m; 0, 0.8 or 1.5 MBq) by tumor-volume measurements. The injected activities for therapies were estimated from separate biodistribution and myelotoxicity studies. Results Tumor targeting of At-211-A11 was efficient and the effect on s.c. macrotumors was strong and dose-dependent. At 6 weeks, the mean tumor volumes for the treated groups, compared with controls, were reduced by approximately 85%. The separate myelotoxicity study following one single fraction showed reduced white blood cells (WBC) for all treated groups on day 6 after treatment. For the 0.8 and 1.5 MBq, the WBC reductions were transient and followed by recovery at day 13. For 2.4 MBq, a clear toxicity was observed and the mice were sacrificed on day 7. In the long-term follow-up of the 0.8 and 1.5 MBq-groups, blood counts on day 252 were normal and no signs of radiotoxicity observed. Efficacy on i.t. microtumors was evaluated in two experiments. In experiment 1, the tumor-free fraction (TFF) was 95% for both treated groups and significantly different (p < 0.05) from the controls at a TFF of 66%). In experiment 2, the difference in TFF was smaller, 32% for the treated group versus 20% for the controls. However, the difference in microtumor volume in experiment 2 was highly significant, 0.010 +/- 0.003 mm(3) versus 3.79 +/- 1.24 mm(3) (treated versus controls, respectively), i.e., a 99.7% reduction (p < 0.001). The different outcome in experiment 1 and 2 is most likely due to differences in microtumor sizes at therapy, or higher tumor-take in experiment 2 (where more cells were implanted). Conclusion Evaluating fractionated alpha-RIT with At-211-labeled anti-PSCA A11 minibody, we found clear growth inhibition on both macrotumors and intratibial microtumors. For mice treated with multiple fractions, we also observed radiotoxicity manifested by progressive loss in body weight at 30 to 90 days after treatment. Our findings are conceptually promising for a systemic TAT of mCRPC and warrant further investigations of At-211-labeled PSCA-directed vectors. Such studies should include methods to improve the therapeutic window, e.g., by implementing a pretargeted regimen of alpha-RIT or by altering the size of the targeting vector.
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| 4. |
- Leidermark, Erik, 1981, et al.
(författare)
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Estimating the risk for secondary cancer following targeted alpha therapy with astatine-211 intraperitoneal radioimmunotherapy.
- 2022
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Ingår i: Journal of nuclear medicine : official publication, Society of Nuclear Medicine. - : Society of Nuclear Medicine. - 1535-5667. ; 64:1, s. 165-172
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Tidskriftsartikel (refereegranskat)abstract
- Intraperitoneal 211At-based targeted alpha therapy (TAT) may hold most promise as an adjuvant therapy following surgery and chemotherapy in epithelial ovarian cancer to eradicate any remaining undetectable disease. This implies it will also be delivered to patients possibly already cured by the primary treatment. An estimate of long-term risks is therefore sought whether to justify the treatment. Methods: Baseline data for risk estimates of alpha-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 for our previously reported dosimetry for intraperitoneal (i.p.) 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 two groups. In the lower ERR/Gy group, up to approx. 5, were: Trachea, bronchus and lung 0.52 (CI 95% 0.21-0.82), Stomach 1.4 (CI 95% -5.0-7.9), Lymphoid and hematopoietic system 2.17 (CI 95% 1.7-2.7), Bone and articular cartilage 2.6 (CI 95% 2.0-3.3), Breast 3.45 (CI 95% -10-17) and Colon 4.5 (CI 95% -3.5-13). In the higher ERR/Gy group, ranging from approx. 10 to 15 were: Urinary bladder 10.1 (CI 95% 1.4-23), Liver 14.2 (CI 95% 13-16), Kidney 14.9 (CI 95% 3.9-26) and Lip, oral cavity and pharynx 15.20 (CI 95% 2.73-27.63). Applying a typical candidate patient (female, age 65 years) and correcting for reference population mortality rate, a total estimated excess mortality of an i.p. 211At-mAb treatment amounted to 1.13 per 100 treated. More than half of 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 - 1.84 per 100 treated. Conclusion: Published epidemiological data on life-long detriment following alpha-particle irradiation and its dosimetry allowed calculations to estimate the risk for secondary cancer following 211At-based i.p. TAT. Measures to reduce dose to the urinary organs may further decrease the estimated relative low risk for secondary cancer from 211At-mAb based i.p. TAT.
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| 5. |
- Lindegren, Sture, 1960, et al.
(författare)
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Realizing Clinical Trials with Astatine-211: The Chemistry Infrastructure
- 2020
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Ingår i: Cancer Biotherapy and Radiopharmaceuticals. - : Mary Ann Liebert Inc. - 1084-9785 .- 1557-8852. ; 35:6, s. 425-436
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Tidskriftsartikel (refereegranskat)abstract
- Despite the consensus around the clinical potential of the alpha-emitting radionuclide astatine-211 (At-211), there are only a limited number of research facilities that work with this nuclide. There are three main reasons for this: (1) Scarce availability of the nuclide. Despite a relatively large number of globally existing cyclotrons capable of producing(211)At, few cyclotron facilities produce the nuclide on a regular basis. (2) Lack of a chemical infrastructure, that is, isolation of(211)At from irradiated targets and the subsequent synthesis of an astatinated product. At present, the research groups that work with(211)At depend on custom systems for recovering(211)At from the irradiated targets. Setting up and implementing such custom units require long lead times to provide a proper working system. (3) The chemistry of(211)At. Compared with radiometals there are no well-established and generally accepted synthesis methods for forming sufficiently stable bonds between(211)At and the tumor-specific vector to allow for systemic applications. Herein we present an overview of the infrastructure of producing(211)At radiopharmaceuticals, from target to radiolabeled product including chemical strategies to overcome hurdles for advancement into clinical trials with(211)At.
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| 6. |
- Maresova, A., et al.
(författare)
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Improved syntheses of P2X(7) ligands based on substituted benzyl amide of pyroglutamic acid motif labelled with iodine-123 or iodine-125
- 2023
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - 0236-5731.
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Tidskriftsartikel (refereegranskat)abstract
- P2X(7) sites are emerging targets for molecular imaging research, notably in the context of neurodegeneration and inflammatory conditions. Therefore, we prepared a precursor for (radio)iodination of the P2X(7) ligand VPGIS191. We then developed a radioiodination method with I-123 for SPECT with a radiochemical yield of 71 +/- 13% and I-125 for autoradiography with a radiochemical yield of 85 +/- 6% Autoradiography of [I-125]VPGIS191 in mouse brain cryostat sections demonstrated approximately 36 nM binding affinity and B-max of approximately 400 pmol/gram tissue for P2X(7) binding sites. VPGIS191 (cis) had a two-fold lower affinity compared to its geometric trans-isomer TZ6019.
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| 7. |
- Palm, Stig, 1964, et al.
(författare)
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Evaluation of therapeutic efficacy of 211At-labeled farletuzumab in an intraperitoneal mouse model of disseminated ovarian cancer
- 2021
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Ingår i: Translational Oncology. - : Elsevier BV. - 1936-5233. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Antibodies labeled with alpha-emitter astatine-211 have previously shown effective in intraperitoneal (i.p.) treatments of ovarian cancer. In the present work we explore the use of investigational farletuzumab, aimed at the folate receptor alpha. The aim was to evaluate the biodistribution and therapeutic effect of 211At-farletuzumab in in-vitro and in-vivo experiments and, using models for radiation dosimetry, to translate the findings to expected clinical result. The activity concentration used for therapy in mice (170 kBq/mL) was chosen to be in agreement with an activity concentration that is anticipated to be clinically relevant in patients (200 MBq/L). Methods: For biodistribution, using intravenous injections and mice carrying subcutaneous (s.c.) tumors, the animals were administered either 211At-farletuzumab (n = 16); or with a combination of 125I-farletuzumab and 211At-MX35 (n = 12). At 1, 3, 10 and 22 h, mice were euthanized and s.c.-tumors and organs weighted and measured for radioactivity. To evaluate therapeutic efficacy, mice were inoculated i.p. with 2 × 106 NIH:OVCAR-3 cells. Twelve days later, the treatments were initiated by i.p.-administration. Specific treatment was given by 211At-labeled farletuzumab (group A; n = 22, 170 kBq/mL) which is specific for OVCAR-3 cells. Control treatments were given by either 211At-labeled rituximab which is unspecific for OVCAR-3 (group B; n = 22, 170 kBq/mL), non-radiolabeled farletuzumab (group C; n = 11) or PBS only (group D; n = 8). Results: The biodistribution of 211At-farletuzumab was similar to that with 125I as radiolabel, and also to that of 211At-labeled MX35 antibody. The tumor-free fraction (TFF) of the three control groups were all low (PBS 12%, unlabeled specific farletuzumab 9% and unspecific 211At-rituximab 14%). TFF following treatment with 211At-farletuzumab was 91%. Conclusion: The current investigation of intraperitoneal therapy with 211At-farletuzumab, delivered at clinically relevant 211At-mAb radioactivity concentrations and specific activities, showed a 6 to 10-fold increase (treated versus controls) in antitumor efficacy. This observation warrants further clinical testing. © 2020 The Authors
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| 8. |
- Sporer, E., et al.
(författare)
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Covalent core-radiolabeling of polymeric micelles with125I/211At for theranostic radiotherapy
- 2022
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Ingår i: Nanotheranostics. - : Ivyspring International Publisher. - 2206-7418. ; 6:4, s. 388-399
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Tidskriftsartikel (refereegranskat)abstract
- Astatine-211 (211At) is one of the most promising α-emitters for targeted alpha therapy, especially of cancer metastases. However, the lack of a stable isotope, frequent in vivo deastatination, and limited radiochemical knowledge makes it challenging to apply. Here, we report a new strategy for radiolabeling the lipophilic core of polymeric micelles (PMs) with covalently bound211At. The PMs were radiolabeled via either an indirect synthon-based method or directly on the amphipathic block copolymer. The radiochemistry was optimized with iodine-125 (125I) and then adapted for211At, enabling the use of both elements as a potential theranostic pair. PMs that were core-radiolabeled with both125I or211At were prepared and characterized, based on a PEG(5k)-PLGA(10k) co-polymer. The stability of the radiolabeled PMs was evaluated in mouse serum for 21 h, showing radiochemical stability above 85%. After in vivo evaluation of the211At-labeled PMs, 4-5 % ID/g of the211At could still be detected in the blood, showing a promising in vivo stability of the PMs. Further,211At-labeled PMs accumulated in the spleen (20-30 %ID/g) and the liver (2.5-5.5 %ID/g), along with some detection of211At in the thyroid (3.5-9 %ID/g). This led to the hypothesis that deastatination takes place in the liver, whereas good stability of the211At core-radiolabel was observed in the blood. © The author(s).
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| 9. |
- Timperanza, Chiara, et al.
(författare)
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Pretargeted Alpha Therapy of Disseminated Cancer Combining Click Chemistry and Astatine-211
- 2023
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Ingår i: Pharmaceuticals. ; 16:4
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Tidskriftsartikel (refereegranskat)abstract
- To enhance targeting efficacy in the radioimmunotherapy of disseminated cancer, several pretargeting strategies have been developed. In pretargeted radioimmunotherapy, the tumor is pretargeted with a modified monoclonal antibody that has an affinity for both tumor antigens and radiolabeled carriers. In this work, we aimed to synthesize and evaluate poly-L-lysine-based effector molecules for pretargeting applications based on the tetrazine and trans-cyclooctene reaction using At-211 for targeted alpha therapy and I-125 as a surrogate for the imaging radionuclides I-123,I- 124. Poly-L-lysine in two sizes was functionalized with a prosthetic group, for the attachment of both radiohalogens, and tetrazine, to allow binding to the trans-cyclooctene-modified pretargeting agent, maintaining the structural integrity of the polymer. Radiolabeling resulted in a radiochemical yield of over 80% for astatinated poly-L-lysines and a range of 66-91% for iodinated poly-L-lysines. High specific astatine activity was achieved without affecting the stability of the radiopharmaceutical or the binding between tetrazine and transcyclooctene. Two sizes of poly-L-lysine were evaluated, which displayed similar blood clearance profiles in a pilot in vivo study. This work is a first step toward creating a pretargeting system optimized for targeted alpha therapy with At-211.
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