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. 2020 Aug 31;35(7):475–484. doi: 10.1089/cbr.2019.3340

Targeted α-Therapy in Cancer Management: Synopsis of Preclinical and Clinical Studies

Hossein Jadvar 1,
PMCID: PMC7475102  PMID: 32202923

Abstract

The approval of 223Ra dichloride (223RaCl2) in 2013 was a principal event in introducing targeted α-therapy as a form of safe and effective management strategy in cancer. There is an increasing interest in research and development of new targeted α-therapy agents spearheaded by advancements in cancer biology, radiochemistry, and availability of clinically relevant α particles. There are active clinical studies on sequencing or combining 223RaCl2 with other drug regimens in the setting of metastatic prostate cancer and in other cancers such as osteosarcoma and bone-dominant breast cancer. Targeted α-therapy strategy is also being actively explored through many preclinical and few early clinical studies using 225Ac, 213Bi, 211At, 227Th, and 212Pb. Investigations incorporating 225Ac are more robust and active at this time with promising results. The author provide a brief synopsis of the preclinical and clinical studies in the rapidly evolving field of targeted α-therapy in cancer management.

Keywords: alpha, cancer, targeted, clinical, preclinical

Introduction

Cancer remains a major public health problem. The scientific community and major research funding agencies have invested heavily in deciphering the complex biology of cancer to improve prevention, diagnosis, and treatment of cancer in the era of precision oncology. Concerted efforts are underway to devise a scientific, regulatory, and policy roadmap with specific priority areas to accelerate translation of bench discoveries to bedside clinical implementation.1 There are traditional (e.g., surgical resection, radiation therapy, cytotoxic chemotherapy) and now many novel (e.g., targeted therapy, immunotherapy) approaches to cancer treatment. Understanding of the underlying cancer biology has expedited precision or personalized therapies targeted to specific biomarkers, which is further facilitated by systematic integration of diagnostics and therapeutics (i.e., theranostics).

Targeted radionuclide therapy (TRT) has been gaining traction recently as a safe and effective form of cancer treatment.2 The classical TRT is more than 75 years old with radioiodine treatment of a patient with thyrotoxicosis by Saul Hertz in 1941 that was soon followed by treatment of patients with thyroid cancer.3,4 Radioiodine therapy with 131I (β and γ emission, half-life = 8.1 d) is based on thyroid biology that traps iodine physiologically. More recently, additional targeted therapies have been approved for patients with neuroendocrine tumors (β particle therapy with 177Lu-DOTATATE or Lutathera™), recurrent and/or unresectable pheochromocytoma and paraganglioma (β particle therapy with 131I-iobenguane or Azedra™), and metastatic castrate-resistant prostate cancer (α particle therapy with 223Ra dichloride [223RaCl2] or Xofigo™). While still not approved for clinical use in the United States, there are currently clinical trials on β- and α-particle therapies directed to prostate-specific membrane antigen (PSMA) in patients with metastatic castrate-resistant prostate cancer.5

The approval of 223RaCl2 as the first targeted α therapy (TAT) was a key event in furthering the research and development of TAT in patients with cancer.6 In this article, the author present a brief synopsis of some of the current preclinical and clinical studies that incorporate TAT as a viable form of cancer management arranged by the parent α-emitting radioisotope.

An α-Particle

An α-particle is a positively charged helium ion (2p, 2n, +2e) that is emitted from the nucleus of an unstable atom as it decays to a different atomic nucleus with reduced atomic mass of 4 and reduced atomic number of 2. Alpha particles are energetic with typical kinetic energy of 5–8 MeV traveling at 5% of speed of light losing large amount of energy (high linear energy transfer of about 80 KeV/μm) in a short distance (50–80 μm) in view their electric charge and relatively large mass.7–9 When properly targeted to disease sites, α particles can deposit large amount of energy locally that may lead to cellular apoptosis through catastrophic double-strand DNA breaks in the nucleus. The α-particle cell-killing efficiency is independent of cellular oxygenation. Thus, hypoxic tumor cells, which may be resistant to standard chemoradiation therapy, are vulnerable to targeted α-particle therapy. While the direct damage to cells is at a relatively short range from α-particle deposition, there may be additional damage to neighboring cells through radiation-induced bystander effect. However, the bystander effect is more limited than that with longer range β particles which typically leads to less collateral damage by the α particles to normal cells adjacent to the tumor microenvironment.10 Alpha particles may also prompt abscopal effect resulting in damage to remote cells probably through radiation-induced immune response. Alpha particles may be targeted innately in unconjugated form or home to a site for payload delivery based on conjugation to a biologically relevant, specific, and accessible molecule.11–14

223Ra

Radium is an alkali earth metal in the same column as calcium, strontium, and barium in the table of elements. Radium was discovered by the Madam Curie and Pierre Curie in 1898, for which they shared the Noble prize in physics with Henri Becquerel in 1903. Despite the discovery of radium and realization of its therapeutic potential at the turn of the 20th century, it was not until recently when 223RaCl2 was approved for treatment of cancer.

223Ra is a calcium mimetic and naturally targets the bone hydroxyapatite (Ca10(PO4)6(OH)2) matrix. It is produced from uranium mill tailings or in generator form from 227Ac (half-life of 21.8 years) parent. With a half-life of 11.43 d, 223Ra decays to stable 207Pb with an emitted decay energy distribution of 93.5% α particle, <3.6% β particle, and <1.1% γ radiation.

Preclinical studies

There have been a number of preclinical studies that led to the initial pilot human studies and finally to the landmark Alpharadin in Symptomatic Prostate Cancer (ALSYMPCA) clinical trial. In view of brevity and the fact that 223RaCl2 is approved by the U.S. Food and Drug Administration (FDA) for clinical use, they limit their discussion in this section to other preclinical studies with 223RaCl2.

Although 223RaCl2 naturally targets the osteoblastic zone of the bone matrix, it can also be loaded into delivery carriers such as liposomes, which may be coated with ligands for specific biologic targeting and controlled release.15 Radiation may be associated with abscopal effect. Malams et al. exposed human prostate, breast, and carcinoma cells to sublethal doses of 223Ra in vitro.16 Sublethal dose of 4–10 Gy of 223Ra over 96 h incubation period enhanced CD8+ cytotoxic T cell-mediated lysis of each tumor type which was facilitated by protein expression of major histocompatibility complex, MHC-I, and calreticulin (a chaperone protein that helps direct peptide loading into MHC-I) on tumors for augmented antigen presentation. This study suggested that other than direct 223Ra-induced cell killing, it may have potential utility in combination with immunotherapy. In keeping with these preclinical results, Kwee et al. reported observations in 2 patients that suggested 223RaCl2 abscopal effect with resultant favorable response in untargeted soft tissue disease.17 A recent report also supported the notion that cytotoxic bystander effect of 223RaCl2 can delay growth in human breast cancer cells implanted as bone marrow xenografts in female athymic nude mice.18

Clinical studies

223RaCl2 (Xofigo) is the first in class targeted α-particle therapy that was approved in May 2013 by the U.S. FDA based on the results of the multinational, randomized, double-blind ALSYMPCA clinical trial.19 ALSYMPCA compared 223RaCl2 (50 kBq/kg intravenously every 4 weeks for six doses plus best standard of care) with placebo (saline intravenously every 4 weeks for six doses plus best standard of care) in men with castration-resistant prostate cancer and symptomatic bone metastases (≥2 lesions) and no visceral metastases (lymph nodes up to 3 cm in short axis were acceptable) and who had adequate bone marrow reserve. This phase III clinical trial incorporated 307 patients in the placebo arm and 614 patients in the treatment arm. The clinical trial demonstrated a 3.6-month overall survival benefit with 223RaCl2 in comparison to that with placebo (median, 14.9 vs. 11.3 months; hazard ratio [HR], 0.70; 95% confidence interval [CI], 0.58–0.83; p < 0.001). The overall survival benefit was present regardless of previous docetaxel treatment (3.1-month survival benefit with previous docetaxel use and 4.6-month survival benefit without previous docetaxel use). There was also longer median time to first symptomatic skeletal-related events (median, 15.6 vs. 9.8 months; HR, 0.66; 95% CI, 0.52–0.83; p < 0.001). Additional post hoc ALSYMPCA data analysis has revealed that 223RaCl2 is associated with reduced hospital days per patient with meaningful quality-of-life improvement and slower decline in quality of life over time in comparison to placebo patients and that the benefit is regardless of baseline opioid use.20–24

The observed adverse events in ALSYMPCA trial were mild and manageable. In a 3-year safety follow-up study, 223RaCl2 was associated with low incidence of myelosuppression that was similar or slightly higher than those for the placebo group (Grade 3/4 anemia 13% vs. 13%, neutropenia 2% vs. 1%, thrombocytopenia 7% vs. 2%, for 223Ra and placebo, respectively).21 Baseline predictors for Grade 2–4 hematologic toxicities are extent of disease (6–20 vs. <6 bone metastases) and elevated serum prostate-specific antigen level for anemia, and prior docetaxel chemotherapy, decreased hemoglobin, and decreased platelet levels for thrombocytopenia.25 A recent publication reported on the results of an interim analysis of a global, prospective, noninterventional study (REASSURE) to assess long-term safety of 223RaCl2 in patients with bone metastatic castration-resistant prostate cancer (mCRPC).26 The cohort included 583 patients who were followed for a median duration of 7 months (range 0–20 months). The safety profile of 223RaCl2 was comparable to those reported by other clinical studies and corroborated the observations that drug-related adverse events are more common in patients who have received prior chemotherapy than those patients who had not undergone chemotherapy (63% vs. 48%, respectively). Moreover, patients without prior chemotherapy had a higher proportion of completing the entire prescribed six injections of 223RaCl2 in comparison to patients with prior chemotherapy (63% vs. 45%, respectively). Jadvar et al. reported on their clinical experience in 25 patients 1 year after offering 223RaCl2 at their center.27 About one-quarter of patients completed the entire six-dose treatment. Advancing soft tissue disease was the primary reason for cessation of therapy. A decline in serum alkaline phosphatase was more common than a decline in serum prostate-specific antigen (PSA) level.

Response to 223RaCl2 may be predicted by 18F-NaF PET imaging.28,29 Despite interpatient and intrapatient heterogeneity of absorbed dose estimates to bone metastases, the baseline uptake of 18F-NaF appears to be correlated significantly with the 223RaCl2 localization to the lesion. Further analysis of the ALSYMPCA trial data has also revealed significant total alkaline phosphatase decline by 87% in the 223RaCl2 group vs. 23% in the placebo group by week 12 (p < 0.001). Similar observations were made with lactate dehydrogenase. The decline in serum PSA level was not statistically significant (27% in 223RaCl2 group vs. 14% in the placebo group, p = 0.160). Therefore, both total alkaline phosphatase and lactate dehydrogenase levels are useful for monitoring response to 223RaCl2 therapy, although neither alkaline phosphatase nor lactate dehydrogenase can act as surrogates for overall survival.30 However, another investigation showed that overall survival was correlated with alkaline phosphatase level.31

There have been a number of studies that have focused on sequencing or combining 223RaCl2 with other available therapies (e.g., sipuleucel-T, abiraterone acetate, enzalutamide, pembrolizumab, atezolizumab, niraparib, olaparib, and paclitaxel) in the clinical setting of men with mCRPC.32 Studies have shown that 223RaCl2 is effective regardless of prior docetaxel and that additional chemotherapy following 223RaCl2 is feasible and well-tolerated.33,34 Morris et al. performed a phase I dose escalation and a randomized phase IIa trial combining 223RaCl2 with docetaxel in patients with castration-resistant prostate cancer and bone metastases.35 The end points were safety, efficacy, and treatment-related changes in serum and imaging biomarkers. The dose escalation study included 20 patients for the purpose of defining the recommended phase II dose (RP2D). The RP2D was determined to be 223RaCl2 at 55 kBq/kg every 6 weeks × 5 doses plus docetaxel 60 mg/m2 every 3 weeks × 10 doses with febrile neutropenia as the dose limiting factor. The 2:1 randomized phase IIa portion of the investigation compared the combination arm at RP2D with docetaxel at a dose of 75 mg/m2 every 3 weeks. The combination arm had longer median time to PSA progression than the monochemotherapy arm (6.6 vs. 4.8 months, respectively). Similar observations were made with median time to alkaline phosphatase progression and osteoblastic bone findings on imaging. Similar encouraging results have been reported with 223RaCl2 in combination with paclitaxel.36

Of the ongoing clinical trials on combination therapies, the trial on 223RaCl2 plus abiraterone acetate has produced interesting results suggesting that while combination therapies may be effective, they may not always be safe. Smith et al. reported on an international, multicenter, randomized, double-blind, placebo-controlled, phase III trial on 806 patients who received either 223RaCl2 (401 patients) or placebo (405 patients) in addition to abiraterone acetate (abi) plus prednisone or prednisolone.37 Eligible patients had progressive chemotherapy-naive asymptomatic or mildly symptomatic castration-resistant prostate cancer with bone metastases. The primary endpoint was symptomatic skeletal event-free survival. The study was unblinded early when an interim analysis showed more fractures and deaths in the combined 223RaCl2 and abiraterone acetate group in comparison to the combined placebo and abiraterone acetate group. Median symptomatic skeletal event-free survival was 22.3 months in radium+abi group and 26.0 months in the placebo+abi group. Fractures occurred in 29% and 11% of the radium+abi and placebo+abi groups, respectively. This trial concluded that combined radium+abi did not improve symptomatic skeletal event-free survival in patients with castration-resistant prostate cancer and bone metastases. Van der Doelen et al. summarized the data on the updated interim analysis noting that majority of extra fractures in the radium+abi group were at sites with no bone metastases (i.e., not pathologic fracture).38 Fractures occurred more frequently in patients with osteoporosis, those who did not receive concurrent bone health agents (e.g., bisphosphonates, denosumab), or had lower number of bone metastases at baseline (<6 vs. ≥6). In view of these observations, the European Medicines Agency (EMA) announced the following restriction in September 2018: “Xofigo is contraindicated in combination with abiraterone acetate and prednisone/prednisolone. In addition, Xofigo should not be started in the first 5 d following the last dose of abiraterone and prednisone/prednisolone. Subsequent systemic cancer treatment should not be initiated for at least 30 d after the last administration of Xofigo.” The U.S. FDA has not changed the original package insert information. Interestingly, a more recent prospective phase II trial (eRADicAte) in 31 patients with metastatic castration-resistant prostate cancer treated with combined 223RaCl2 and abiraterone acetate plus prednisone reported improvement in quality life and pain measures without unexpected adverse events.39 The differing conclusions of the currently available data on the utility and limitations of combination use of 223RaCl2 with abiraterone acetate suggest the need for additional investigations in this clinical setting.

The PEACE-3 (NCT02194842) clinical trial is a randomized phase III open label trial to assess if upfront combination of enzalutamide (160 mg daily) and 223RaCl2 (50 kBq/kg standard dose monthly for 6 months) improves radiological progression-free survival (defined by the Prostate-Cancer clinical trials Working Group 2) compared to enzalutamide alone (160 mg daily) in asymptomatic or mildly symptomatic castration-resistant prostate cancer bone metastases. The trial is currently recruiting patients and is anticipated to be completed in April 2021.

Sartor et al. reported on a prospective phase I/II study of 44 patients who were retreated with 223RaCl2 after completing the initial six cycles of 223RaCl2 therapy without on-treatment progression of osseous metastatic disease.40 In this cohort, approximately two-thirds of the patients completed all six retreatment administrations with no major adverse events, suggesting that in a subset of patients with stable bone metastases, retreatment with 223RaCl2 may be a viable therapeutic option.

There has also been an interest in exploring the use of 223RaCl2 earlier in the continuum of metastatic prostate cancer (i.e., metastatic castration-sensitive prostate cancer). Osvaldo et al. reported on their initial experience with the feasibility, safety, and efficacy (decline in bone pain) of combining 223RaCl2 and androgen deprivation therapy in 7 men with mCSPC.41 Another small-scale study of 10 patients with mCSPC after radical prostatectomy demonstrated similar findings of reduced bone pain based on self-reporting Brief Pain Inventory questionnaire with median decrease of 36% after three cycles and 40% after end of all six therapy cycles.42 Potential efficacy of 223RaCl2 combined with androgen deprivation therapy and stereotactic body radiation therapy of patients with oligometastatic disease (<4 metastases on conventional imaging) is also being explored.43

Although 223RaCl2 has been approved since 2013 for treatment of patients with castration-resistant prostate cancer and bone metastases, there have been other active investigations on the potential use of 223RaCl2 in cancers other than prostate cancer (e.g., osteosarcoma, bone-dominant breast cancer).44,45 Dizdarevic et al. provides an excellent recent review of 223RaCl2 mono- or combination trials in prostate cancer and other tumors.46

225Ac

Actinium-225 is another potentially useful α-emailer in TRT. It has a half-life of 9.9 d and decays to 209Bi (half-life of 1.9 × 1019 years) through net production of four α particles with energies in the range of 5.8–8.4 MeV at tissue travel distance of 47–85 μm, two β particles, and γ emissions at 218 and 440 KeV. 225Ac may be sourced from 229Th with current worldwide production of ∼68 GBq per year which is anticipated to grow.47–49 The National Isotope Development Centers provide alerts when new batches of the accelerator-produced 225Ac are available through the U.S. Department of Energy Isotope Program.

Preclinical studies

There is a fair range of preclinical studies in various cancers that have demonstrated the potential utility of 225Ac for targeted therapy.50 Kelly et al. showed that a single dose of 148 kBq 225Ac conjugated to albumin-binding PSMA-targeting RPS-074 (225Ac-RPS-074) in LNCaP xenograft mouse model of human prostate cancer induced a complete response in six of seven tumors without major toxic effects.51 Lower doses produced transient partial responses. More recently, researchers reported on a useful mouse model of human metastatic prostate cancer by injecting C4–2 cells into the left ventricle of immunodeficient male NSG mice, which was then used to evaluate the effectiveness of 225Ac-PSMA-617 at various disease stages.52 This preclinical study suggested that early 225Ac-PSMA-617 intervention is more efficacious in the setting of widespread metastatic prostate cancer. Delivery to tumor may also be accomplished by loading 225Ac into PEGylated liposomes targeted to mouse antihuman PSMA J591 antibody or A10 PSMA aptamer.53 Liposomes when loaded with 225Ac or other α-emitters are attractive delivery systems since they can be modified in various ways selectively to improve therapeutic efficacy.54

Encouraging results have been reported with in vitro experiments utilizing an antihuman epidermal growth factor type 2 (HER-2) nanobody (225Ac-DOTA-Nb) in tumor cells overexpressing HER-2.55 Mouse models of human ductal carcinoma in situ tumor treated with 225Ac-trastuzumab targeting HER2/neu also demonstrated utility as a worthwhile treatment modality without renal toxicity.56,57

In diseases that are challenging to eradicate such as peritoneal carcinomatosis, TAT may provide a useful therapeutic option. German investigators showed that in mice bearing intraperitoneal MDA-MB-435 xenograft tumors, both vascular tumor-homing peptide F3 targeted with 225Ac-DOTA-F3 and 213Bi-DTPA-F3 and administrated intraperitoneally prolonged median survival in treated mice with mild renal toxicity in comparison to control untreated mice.58

Melanocortin 1 receptor (MC1R) may be used as a relevant biological target for treatment of melanoma. In a recent report, Tafreshi et al. evaluated 225Ac-DOTA-MC1R radioligand in BALB/c mice bearing MC1R-positive and -negative tumors demonstrating the efficacy of the TAT as a potential novel therapy for metastatic uveal melanoma.59

Clinical studies

There have been a number of small clinical studies using TRT with 225Ac as the conjugated α-emitter in a variety of cancers with generally encouraging efficacy and acceptable and/or manageable safety profile. Jurcic reported on a phase I study of 18 patients with relapsed or refractory acute myeloid leukemia who underwent anti-CD33 humanized monoclonal antibody treatment with 225Ac-lintuzumab for doses up to 111 kBq/kg demonstrating up to 28% objective responses.60

There has been much interest in potential efficacy of 225Ac-labeleled PSMA-targeted in treatment of patients with mCRPC. Some of these early experiences, mostly as case reports or small case series, have been encouraging with remarkable favorable responses in individual patients although at some cost with xerostomia.61 Kratochwil et al. from Germany reported on dosimetry estimates and empiric dose finding for targeted therapy of mCRPC with 225Ac-PSMA-617.62 The author found that a treatment activity of 100 kBq/kg of 225Ac-PSMA-617 per cycle every 8 weeks was an apparent optimal trade-off between toxicity and biochemical efficacy.

213Bi

Bismuth-213 is an α-emitter that has received attention for potential clinical use. 213Bi emits both α (∼92.7%) and β (∼7.3%) particles with a relatively short half-life of 46 min. The 8.375 MeV α particle that is emitted by 213Po along the decay path of 213Bi comprises more than 98% of the α-particle energy from 213Bi disintegration.63 The decay cascade also includes 26.1% probability of 440 KeV γ-ray emission that allows imaging the 213Bi biodistribution.

Preclinical studies

There has been an increasing interest in the use of TAT in the setting of metastatic prostate cancer spearheaded by the approval of 223RaCl2.64An in-vitro and LNCaP xenograft animal model study of two PSMA targeted α-radioligands (213Bi-PSMA I&T and 213Bi-JVZ-008) confirmed α-particle induced double-strand DNA damage.65 An investigation using a prostate cancer animal model compared 213Bi-DOTA-PESIN (DOTA-PEG(4)-bombesin) and 213Bi-AMBA (DO3A-CH(2)CO-8-aminooctanoyl-Q-W-A-V-G-H-L-M-NH(2)) with 177Lu-DOTA-PESIN reported that α particle therapy with either of 2 agents tested was more efficacious than the counterpart β particle agent therapy.66 McDevitt and colleague used 213Bi-J591 targeted to PSMA directed against androgen-sensitive LNCaP spheroids resulting in significantly improved median tumor-free survival.67 Radionuclide therapy with 213Bi-labeled plasminogen activator inhibitor type 2 targeting cell surface urokinase plasminogen activator receptor (uPAR) in prostate cancer nude mouse xenograft model has also demonstrated efficacy without major toxicity.68

Another preclinical study with myeloma xenografts treated with 213Bi-anti-CD38-Mab showed evidence for tumor DNA damage and apoptosis that was associated with significantly prolonged animal survival in comparison to untreated control animals.69 Similar results for myeloma have been reported with 213Bi-anti-mCD138 radioimmunotherapy as an alternative to Melphalan.70–72 Therapeutic efficacy with no acute or chronic toxicity has also been shown in a mouse model of gastric cancer with 213Bi-d9 monoclonal antibody targeting d9-E-cadherin.73 Similar good results have been reported in preclinical models of pancreatic neuroendocrine tumors with 213Bi-[DOTA0, Tyr3]octreotide peptide receptor and in pancreatic adenocarcinoma targeting tumor-associated antigen MUC-1 with 213Bi-CHX-A”-C595 leading to regression of tumor cells in vitro and delay and inhibition of tumor growth in vivo.74,75 In breast cancer models, 213Bi-labeled-plasminogen activator inhibitor type 2, 213Bi-Herceptin (targeting HER2/neu), and 213Bi-labeled humanized anti-Lewis Y monoclonal antibody hu3S193 have shown therapeutic efficacy.76–80

In setting of experimental model of lymphoma, 213Bi-labeled anti-CD74 showed suppression of tumor growth and in some cases cures.81 Therapeutic efficacy with 213Bi-anti-CD45 antibodies has been shown in leukemic cells overcoming DNA repair mechanisms and chemoradioresistance.82 Kennel et al. showed that 213Bi-mAb 201B targeted to lung blood vessels can effectively control tumors growing in the lung.83 Swedish investigators showed the potential efficacy of 213Bi-labeled monoclonal antibody MX35 in intraperitoneally inoculated human ovarian cancer cells in female BALB/c (nu/nu) mice.84 Similar efficacy has been shown with 213Bi-DTPA-F3 targeting vascular tumor-homing peptide F3 in combination with paclitaxel in treating intraperitoneal OVCAR-3 tumor xenografts.85

Delivery of 213Bi via immunoliposomal vehicles has also been demonstrated in a rat/neu transgenic mouse model of metastatic breast cancer targeting HER-2/neu expressing tumors.86 An in vitro study assessed the effect of hypoxia on cellular killing efficacy of 213Bi-anti-epidermal growth factor receptor (EGFR).87 Cell death was shown to be independent of cellular oxygenation, which suggests sensitivity of hypoxic cells to α therapy in competitive advantage over chemoradiotherapy.

Clinical studies

Krolicki et al. used 213Bi-substance P (213Bi-DOTA-SP) radioligand therapy, targeted to neurokinin type 1 receptor, to treat 50 patients with recurrent glioblastoma multiforme by injecting the radioligand (1–6 doses of 0.9–2.3 GBq in 2 months intervals) into the tumor cavity.88 Proper localization of the therapy radioligand was confirmed with coinjection of 68Ga-DOTA-SP. The median progression-free survival and overall survival were 5.8 and 16.4 months, respectively, with transient headache as the main side effect. In another recent study from the same group of investigators, one to seven therapy doses of activity up to 11.2 GBq at 2-month intervals in 20 patients with recurrent glioblastoma multiforme was noted to be safe and well-tolerated with overall survival benefit compared to historical outcome data with conventional therapies.89 Others have reported similar findings in the clinical settings of functional critically located gliomas and low-grade gliomas.90,91 Although these are encouraging results for tumor control in this challenging disease, prospective studies with proper controls are needed to assess the incremental outcome benefit with this form of TRT.

Preclinical and follow-up clinical studies have investigated the intravesical administration of 213Bi-immunoconjugate targeting EGFR in treating 12 patients with biopsy-proven carcinoma-in-situ of the urinary bladder refractory to bacillus Calmette-Guerin therapy.92,93 These author showed well-tolerated efficacy in this limited number of patients and suggested a phase I clinical trial to be followed. In patients with metastatic melanoma, efficacy of local metastasis-directed therapy with intralesional injection of 213Bi immunoconjugate targeting vector 9.2.27 has been shown to be efficacious.94 Such approach may be workable in the setting of metastatic-directed therapy in oligometastatic disease, which is of much current interest as a form of interim management approach in lieu of systematic therapy.

As previously discussed, α particle therapy targeted to the PSMA is efficacious and a topic of major interest in research. Sathekge et al. from South Africa presented a case report of a patient with mCRPC who demonstrated exceptional response to 213Bi-PSMA-617 therapy.95

211At

Preclinical and clinical studies

Astatine-211 is an α-emitter radiohalogen with half-life of 7.2 h with mean energy of 6.9 MeV with a currently limited availability.96 Vaidyanathan and Zalutsky provide an excellent review of potential applications of 211At.97 Kennel et al. showed efficacy against lung tumor colonies of EMT-6 cells using lung blood vessel-targeting monoclonal antibody 201B with N-succinimidyl N-(4-[211At-[astatophenethyl) succinamate linker.98 Other preclinical studies have been reported in settings of leukemia (211At-anti-CD25 monoclonal antibody 7G7/B6), metastatic melanoma (211At-methylene blue), and peritoneal carcinomatosis (211At-microsphere colloids), and 131I-refractory metastatic thyroid cancer.99–102 In the clinical arena, 12 patients with relapsed epithelial ovarian cancer were treated with intraperitoneal administration of 215 MBq/L of 211At-MX25 F(ab′)2.103 No signs of radiation-induced toxicity were noted and dosimetric calculations suggested that further dose optimization can be performed to increase efficacy.

227Th

Preclinical studies

Thorium-227 is another α-emitting radioisotope that is gaining traction in TRT of cancer. It has a half-life of 19 d decaying first to 223Ra and then follows the decay of 223Ra.

A preclinical study reported on mesothelin (MSLN)-targeted conjugate of 227Th, comprising fully human IgG1 antibody BAY 86–1903, covalently conjugated to a 3,2-HOPO chelator enabling stable complexation of 227Th.104 MSLN is 40 kDa membrane-anchored glycoprotein expressed in mesothelial cells lining of pleura, pericardium, and peritoneum, which is thought to be involved in cell adhesion and is overexpressed in many cancers. Hagemann et al. showed the potential value of 227Th-MSLN conjugate in vitro and in vivo in cell line and patient-derived xenograft (PDX) models of breast, colorectal, lung, ovarian, and pancreatic cancers.104 Wickstroem et al. evaluated the efficacy of 227Th-MSLN conjugate in combination with the DNA damage response inhibitor, olaparib, in the OVCAR-3 xenograft model.105 The encouraging results have prompted a first human study of such construct in patients with MSLN expressing tumors (NCT03507452). In the preclinical setting of athymic nude mouse model of intraperitoneal human ovarian carcinoma (SKOV3-luc-D3 cells), targeted therapy with 227Th-trastuzumab has been found to be more efficacious than unlabeled trastuzumab anti-HER2 therapy.106

As declared above, PSMA has been identified as a clinically valuable biomarker for theranostics in prostate cancer. In addition to reports on 225Ac- and 213Bi-labeled PSMA-based agents described previously, Hammer et al. described the preclinical efficacy of 227Th-PSMA conjugates in PDX models of prostate cancer, which prompted an ongoing phase I trial in patients with mCRPC (NCT03724747).107 Synergistic efficacy has also been demonstrated with HER2 targeted 227Th conjugates in combination with DNA repair inhibitor drug, olaparib (poly ADP ribose polymerase inhibitor) in BRCA2 deficient xenograft tumor models.108 The same group of investigators have also reported on the potential utility of 227Th conjugates targeting the fibroblast growth factor receptor 2 (FGFR2), which is overexpressed in many cancers, and in acute myeloid leukemia targeting CD33.109,110

212Pb

Preclinical and clinical studies

Pb-212 is a β-emitter (half-life 10.64 h) and serves as an in vivo nanogenerator of 212Bi (half-life 1.01 h), which decays to stable 208Pb via α-particle emission. Yong and Brechbiel provide a comprehensive review of 212Pb in targeted α-particle therapy of cancer.111,112

Recently, the group of investigators from Johns Hopkins University reported on a proof-of-concept therapy study of dose-dependent inhibition of human prostate tumor growth in PSMA+ tumors in animal hosts.113 The tumor evolution could be monitored with scintigraphy using the surrogate radionuclide, 203Pb (half-life 51.9 h, γ = 279 KeV) using single-photon computed tomography, supporting the notion of 203Pb/212Pb as a relevant and useful theranostic radionuclide pair.114

Preclinical efficacy of 212Pb-labeled antivascular cell adhesion molecule-1 (VCAM-1) in treatment of brain metastases of human breast cancer cells injected into the left ventricle of nude mice has been demonstrated.115 Similar encouraging results have been noted in animal models of 212Pb-DOTAMTATE in treatment of somatostatin receptor overexpressing neuroendocrine tumors.116 Kasten et al. evaluated the potential therapeutic utility of 212Pb-labled antibody 225.28 targeted to chondroitin sulfate proteoglycan 4 in triple negative breast cancer.117 These author found that 212Pb-225.28 was effective in eliminating triple negative breast cancer tumors in xenograft and orthotopic animal models. Same investigators reported similar results with therapeutic efficacy of 212Pb-labeled B7–H3 targeting human pancreatic ductal adenocarcinoma and ovarian cancer xenografts in immunodeficient mice.118,119 Milenic et al. performed preclinical studies of 212Pb-cetuximab targeted to HER1-positive disseminated peritoneal carcinomatosis showing such TRT may be potentially useful clinically.120

First-in-human studies of 212Pb-TCMC-trastuzumab therapy of HER2-positive intraperitoneal ovarian cancer metastases have been shown to be safe, although efficacy needs further investigations to be established.121,122

Summary

The author summarized some of the preclinical and clinical studies in the setting of targeted α-therapy. 223RaCl2 is an established first-in-class targeted α-therapy in metastatic castration-resistant prostate cancer with bone metastases. Many preclinical and early clinical studies are also being pursued with 225Ac, 213Bi, 211At, 227Th, and 212Pb of which those with 225Ac are more robust and probably closer to translation into the clinic. Targeted α-particle therapy is destined to become an important strategy within the armamentarium of cancer management in the near future.

Disclosure Statement

No competing financial interests exist.

Funding Information

Supported, in part, by grants R21-EB017568 and P30-CA014089 from the National Institutes of Health.

References

  • 1. Jaffee EM, Dang C, Agus DB, et al. Future cancer research priorities in the USA: A Lancet Oncology Commission. Lancet Oncol 2017;18:653. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2. Allen BJ, Raja C, Rizvi S, et al. Targeted alpha therapy for cancer. Phys Med Biol 2004;49:3703. [DOI] [PubMed] [Google Scholar]
  • 3. Jadvar H, Chen X, Cai W, et al. Radiotheranostics in cancer diagnosis and management. Radiology 2018;286:388. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4. Jadvar H. Targeted radionuclide therapy: An evolution toward precision cancer treatment. AJR Am J Rontgenol 2017;209:277. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5. Rahbar K, Afshar-Oromieh A, Jadvar H, et al. PSMA theranostics: Current status and future directions. Mol Imaging 2018;17:1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 6. Pandit-Taskar N, Larson SM, Carrasquillo JA. Bone-seeking radiopharmaceuticals for treatment of osseous metastases: Part 1: a therapy with 223Ra-dichloride. J Nucl Med 2014;55:268. [DOI] [PubMed] [Google Scholar]
  • 7. Poty S, Francesconi LC, McDevitt MR, et al. α-emitters for radiotherapy: From basic radiochemistry to clinical studies—Part 1. J Nucl Med 2018;59:878. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8. Poty S, Francesconi LC, McDevitt MR, et al. α-emitters for radiotherapy: From basic radiochemistry to clinical studies—Part 2. J Nucl Med 2018;59:1020. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9. Brechbiel MW. Targeted a-therapy: Past, present, future? Dalton Trans 2007;43:4918. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10. Marcu L, Bezak E, Allen BJ. Global comparison of targeted alpha vs targeted beta therapy for cancer: In vitro, in vivo, and clinical trials. Crit Rev Oncol Hematol 2018;123:7. [DOI] [PubMed] [Google Scholar]
  • 11. Jadvar H, Quinn DI. Targeted a-particle therapy of bone metastases in prostate cancer. Clin Nucl Med 2013;38:966. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 12. Parker C, Lewington V, Shore N, et al. Targeted alpha therapy: An emerging class of cancer agents: A review. JAMA Oncol 2018;4:1765. [DOI] [PubMed] [Google Scholar]
  • 13. Wadas TJ, Pandya DN, Solingapuram Sai KK, et al. Molecular targeted α-particle therapy for oncologic applications. AJR Am J Ronetgenol 2014;203:253. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14. Zukotynski K, Jadvar H, Capala J, et al. Targeted radionuclide therapy: Practical applications and future prospects. Biomark Cancer 2016;8(Suppl 2):35. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 15. Jonasdottir TJ, Fisher DR, Borrebaek J, et al. First in vivo evaluation of liposomes-encapsulated 223Ra as a potential alpha-particle-emitting cancer therapeutic agent. Anticancer Res 2006;26:2841. [PubMed] [Google Scholar]
  • 16. Malamas AS, Gameiro SR, Knudson KM, et al. Sublethal exposure to alpha radiation (223Ra dichloride) enhances various carcinomas' sensitivity to lysis by antigen-specific cytotoxic T lymphocytes through calreticulin-mediated immunogenic modulation. Oncotaget 2016;7:86937. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17. Kwee SA, Lim J, Coel MN. Soft tissue response on 18F-fluorocholine PET/CT in metastatic castrate-resistant prostate cancer treated with 223Ra-dichloride: A possible abscopal effect? Clin Nucl Med 2017;42:868. [DOI] [PubMed] [Google Scholar]
  • 18. Leung CN, Canter BS, Rajon D, et al. Dose-dependent growth delay of breast cancer xenografts in the bone marrow of mice treated with 223Ra: The role bystander effects and their potential for therapy. J Nucl Med 2020;61:89. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19. Parker C, Nilsson S, Heinrich D, et al. Alpha emitter radium-223 and survival in metastatic prostate cancer. N Engl J Med 2013;369:213. [DOI] [PubMed] [Google Scholar]
  • 20. Parker C, Zhan L, Cislo P, et al. Effect of radium-223 dichloride (Ra-223) on hospitalization: An analysis of from the phase 3 randomized alpharadin in symptomatic prostate cancer patients (ALSYMPCA) trial. Eur J Cancer 2017;71:1. [DOI] [PubMed] [Google Scholar]
  • 21. Parker C, Coleman RE, Sartor O, et al. Three-year safety of radium-223 dichloride in patients with castration-resistant prostate cancer and symptomatic bone metastases from phase 3 randomized alpharadin in symptomatic prostate cancer trial. Eur Urol 2018;73:427. [DOI] [PubMed] [Google Scholar]
  • 22. Parker C, Heidenreich A, Nilsson S, et al. Current approaches to incorporation of radium-223 in clinical practice. Prostate Cancer Prostatic Dis 2018;21:37. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 23. Nilsson S, Cislo P, Sartor O, et al. Patient-reported quality of life analysis of radium-223 dichloride from the phase III ALSYMPCA study. Ann Oncol 2016;27:868. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24. Parker C, Finkelstein SE, Michalski JM, et al. Efficacy and safety of radium-223 dichloride in symptomatic castration-resistant prostate cancer patients with or without baseline opioid use from the phase 3 ALSYMPCA trial. Eur Urol 2016;70:875. [DOI] [PubMed] [Google Scholar]
  • 25. Vogelzang NJ, Coleman RE, Michalski JM, et al. Hematologic safety of radium-223 dichloride: Baseline prognostic factors associated with myelosuppression in the ALSYMPCA trial. Clin Gentourin Cancer 2017;15:42. [DOI] [PubMed] [Google Scholar]
  • 26. Dizdarevic S, Petersen PM, Essler M, et al. Interim analysis of the REASSURE (Radium-223 alpha Emitter Agent in non-intervention safety study in mCRPC population for long-teRm Evaluation) study: Patient characteristics and safety according to prior use of chemotherapy in routine clinical practice. Eur J Nucl Med Mol Imaging 2019;46:1102. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 27. Jadvar H, Challa S, Quinn DI, et al. One-year postapproval clinical experience with Radium-223 dichloride in patients with metastatic castration-resistant prostate cancer. Cancer Biother Radiopharm 2015;30:195. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 28. Murray I, Chittenden SJ, Denis-Bacelar AM, et al. The potential of 223Ra and 18F-fluoride imaging to predict bone lesion response to treatment with 223Ra-dichloride in castration-resistant prostate cancer. Eur J Nucl Med Mol Imaging 2017;44:1832. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 29. Iagaru AH, Mittra E, Colletti PM, et al. Bone-targeted imaging and radionuclide therapy in prostate cancer. J Nucl Med 2016;57(Suppl 3):19S. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 30. Sartor O, Coleman RE, Nilsson S, et al. An exploratory analysis of alkaline phosphatase, lactate dehydrogenase, and prostate-specific antigen dynamics in the phase 3 ALSYMPCA trial with radium-223. Ann Oncol 2017;28:1090. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 31. Dizdarevic S, Jessop M, Begley P, et al. 223Ra-dichloride in castration-resistant metastatic prostate cancer: Improving outcomes and identifying predictors of survival in clinical practice. Eur J Nucl Med Mol Imaging 2018;45:2264. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32. Den RB, George D, Pieczomka C, et al. Ra-223 treatment for bone metastases in castrate-resistant prostate cancer: Practical management issues for patient selection. Am J Clin Oncol 2019;42:399. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 33. Sartor O, Hoskin P, Coleman RE, et al. Chemotherapy following radium-223 dichloride treatment in ALSYMPCA. Prostate 2016;76:905. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 34. Hoskin P, sartor O, O'Sullivan JM, et al. Efficacy and safety of radium-223 dichloride in patients with castration-resistant prostate cancer and asymptomatic bone metastases, with or without previous docetaxel use: A prespecified subgroup analysis from the randomized, double-blind, phase 3 ALSYMPCA trial. Lancet Oncol 2014;15:1397. [DOI] [PubMed] [Google Scholar]
  • 35. Morris MJ, Loriot Y, Sweeney CJ, et al. Radium-223 in combination with docetaxel in patients with castration-resistant prostate cancer and bone metastases: A phase 1 dose escalation/randomized phase 2a trial. Eur J Cancer 2019;114:107. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 36. Geva R, Lopez J, Danson S, et al. radium-23 in combination with paclitaxel in cancer patients with bone metastases: Safety results from an open-label multicenter phase 1b study. Eur Nucl Med Mol Imaging 2019;46:1092. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 37. Smith M, Parker C, Saad F, et al. Addition of radium-223 to abiraterone acetate and prednisone or prednisolone in patients with castration-resistant prostate cancer and bone metastases (ERA 223): A randomized, double-blind, placebo-controlled, phase 3 trial. Lancet Oncol 2019;20:408. [DOI] [PubMed] [Google Scholar]
  • 38. Van der Doelen MJ, Mehra N, Hermsen R, et al. Patient selection for radium-223 therapy in patients with bone metastatic castration-resistant prostate cancer: New recommendations and future perspectives. Clin Genitourin Cancer 2018;17:79. [DOI] [PubMed] [Google Scholar]
  • 39. Shore ND, Tutrone RF, Mariados NF, et al. eRADicAte: A prospective evaluation combining radium-223 dichloride and abiraterone acetate plus prednisone in patients with castration- resistant prostate cancer. Clin Genitourin Cancer 2018;16:149. [DOI] [PubMed] [Google Scholar]
  • 40. Sartor O, Heinrich D, Mariados N, et al. Re-treatment with radium-223:first experience from an international open-label, phase I/II study in patients with castration-resistant prostate cancer and bone metastases. Ann Oncol 2017;28:2464. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 41. Osvaldo G-P F, Salvador M-O S, Zael S-R, et al. Radium-223 in metastatic hormone-sensitive high-grade prostate cancer: Initial experience. Am J Nucl Med Mol Imaging 2017;7:236. [PMC free article] [PubMed] [Google Scholar]
  • 42. Wenter V, Herlemann A, Fendler WP, et al. Radium-223 for primary bone metastases in patients with hormone-sensitive prostate cancer after radical prostatectomy. Oncotarget 2017;8:44131. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 43. Dandapani SV, Dorff TB, Kortylewski M, et al. Radium 223 dichloride in combination with androgen deprivation therapy and stereotactic body radiation therapy for patients with stage IV oligometastatic castration sensitive prostate cancer: Clinical trial in progress. Int J Radiat Oncol Biol Phys 2019;104:1193 [Google Scholar]
  • 44. Coleman R, Aksnes AK, Nume B, et al. A phase IIa, nonrandomized study of radium-223 dichloride in advanced breast cancer patients with bone-dominant disease. Breast Cancer Re Treat 2014;145:411. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 45. Subbiah V, Anderson PM, Kairemo K, et al. Alpha particle radium 223 dichloride in high-risk osteosarcoma: A phase I dose escalation trial. Clin Cancer Res 2019;25:3802. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 46. Dizdarevic S, McCready R, Vinjamuri S. Radium-223 dichloride in prostate cancer: Proof of principle for the use of targeted alpha treatment in clinical practice. Eur J Nucl Med Mol Imaging 2020;47:192. [DOI] [PubMed] [Google Scholar]
  • 47. Morgenstern A, Apostolidis C, Kratochwil C, et al. An overview of targeted alpha therapy with 225Actinium and 213Bismuth. Curr Radiopharm 2018;11:200. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 48. Mulford DA, Scheinberg DA, Jurcic JG. The promise of targeted α-particle therapy. J Nucl Med 2005;46:198S. [PubMed] [Google Scholar]
  • 49. Harvey JT. NorthStar perspectives for actinium-225 production at commercial scale. Curr Radiopharm 2018;11:180. [DOI] [PubMed] [Google Scholar]
  • 50. Scheinberg DA, McDevitt MR. Actinium-225 in targeted alpha-particle therapeutic applications. Curr Radiopharm 2011;4:306. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 51. Kelly JM, Amor-Coarasa A, Ponnala S, et al. A single dose of 225Ac-RPS-074 induces a complete tumor response in an LNCaP xenograft model. J Nucl Med 2019;60:649. [DOI] [PubMed] [Google Scholar]
  • 52. Stuparu AD, Meyer CAL, Evans-Axelsson SL, et al. Targeted alpha therapy in a systemic mouse model of prostate cancer—A feasibility study. Theranostics 2020;10:2612. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 53. Bandekar A, Zhu C, Jindal R, et al. Anti-prostate-specific membrane antigen liposomes loaded with 225Ac for potential targeted antivascular a-particle therapy of cancer. J Nucl Med 2014;55:107. [DOI] [PubMed] [Google Scholar]
  • 54. Chang MY, Seiderman J, Sofou S. Enhanced loading efficiency and retention of 225Ac in rigid liposomes for potential targeted therapy of micrometastases. Bioconjug Chem 2008;19:1274. [DOI] [PubMed] [Google Scholar]
  • 55. Pruszynski M, D'Huyvetter M, Bruchertseifer F, et al. Evaluation of an anti-HER2 nanobody labeled with 225Ac for targeted α-particle therapy of cancer. Mol Pharm 2018;15:1457. [DOI] [PubMed] [Google Scholar]
  • 56. Song H, Hobbs RF, Vairavelu R, et al. Radioimmuotherapy of breast cancer metastases with alpha-particle emitter 225Ac: Comparing efficacy with 213Bi and 90Y. Cancer Res 2009;69:8941. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 57. Yoshida T, Jin K, Song H, et al. Effective treatment of ductal adenocarcinoma in situ with a HER-2-targeted alpha-particle emitting radionuclide in a preclinical model of human breast cancer. Oncotarget 2016;7:33306. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 58. Essler M, Gartner FC, Neff F, et al. Therapeutic efficacy and toxicity of 225Ac-labelled vs. 213Bi-labelled tumor-homing peptides in a preclinical model mouse model of peritoneal carcinomatosis. Eur J Nucl Med Mol Imaging 2012;39:602. [DOI] [PubMed] [Google Scholar]
  • 59. Tafreshi NK, Tichacek CJ, Pandya DN, et al. Melanocortin 1 receptor targeted alpha-particle therapy for metastatic uveal melanoma. J Nucl Med 2019;60:1124. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 60. Jurcic JG. Clinical studies with bismuth-213 and actininium-225 for hematologic malignancies. Curr Radiopharm 2018;11:192. [DOI] [PubMed] [Google Scholar]
  • 61. Kratochwil C, Bruchertseifer F, Giesel FL, et al. 225Ac-PSMA-617 for PSMA-targeted α-radiation therapy of metastatic castration resistant prostate cancer. J Nucl Med 2016;57:1941. [DOI] [PubMed] [Google Scholar]
  • 62. Kratochwil C, Bruchertseifer F, Rathke H, et al. Targeted a-therapy of metastatic castration-resistant prostate cancer with 225Ac-PSMA-617: Dosimetry estimates and empiric dose finding. J Nucl Med 2017;58:1624. [DOI] [PubMed] [Google Scholar]
  • 63. Morgenstern A, Bruchertseifer F, Apostolidis C. Targeted alpha therapy with 213Bi. Curr Radiopharm 2011;4:295. [DOI] [PubMed] [Google Scholar]
  • 64. Li Y, Song E, Abbas Rizvi SM, et al. Inhibition of micrometastases prostate cancer cell spread in animal models by 213Bi-labeled multiple targeted alpha radioimmunoconjugates. Clin Cancer Res 2009;15:865. [DOI] [PubMed] [Google Scholar]
  • 65. Nonnekens J, Chatalic KL, Molkenboer-Kuenen JD, et al. 213Bi-labeled prostate-specific membrane antigen targeting agents induce DNA double-strand breaks in prostate cancer xenografts. Cancer Biother Radiopharm 2017;32:67. [DOI] [PubMed] [Google Scholar]
  • 66. Wild D, Frischknerdt M, Zhang H, et al. Alpha- and beta-particle radiopeptide therapy in a human prostate cancer model (213Bi-DOTA-PESIN and 213Bi-AMBA versus 177Lu-DOTA-PESIN). Cancer Res 2011;71:1009. [DOI] [PubMed] [Google Scholar]
  • 67. McDevitt MR, Barendswaard E, Ma D, et al. An alpha-particle emitting antibody ([213Bi]J591) for radioimmunotherapy of prostate cancer. Cancer Res 2000;60:6095. [PubMed] [Google Scholar]
  • 68. Abbas-Rizvi SM, Li Y, Song EY, et al. Preclinical studies of bismuth-213 labeled plasminogen activator inhibitor type 2 (PAI2) in a prostate cancer nude mouse xenograft model. Cancer Biol Ther 2006;5:386. [DOI] [PubMed] [Google Scholar]
  • 69. Teiluf K, Seidl C, Blechert B, et al. α-radioimmunotherapy with 213Bi-anti-CD38 immunoconjugates is effective in a mouse model of human multiple myeloma. Oncotarget 2015;6:4692. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 70. Couturier O, Faivre-Chauvet A, Filippovich IV, et al. Validation of 213Bi-alpha radioimmunotherapy for multiple myeloma. Clin Cancer Res 1999;5(10 Suppl):3165s. [PubMed] [Google Scholar]
  • 71. Cherel M, Gouard S, Gaschet J, et al. 213Bi raduoimmuotherapy with an anti-mCD138 monoclonal antibody in a murine model of multiple myeloma. J Nucl Med 2013;54:1597. [DOI] [PubMed] [Google Scholar]
  • 72. Gouard S, Pallardy A, Gaschet J, et al. Comparative analysis of multiple myeloma treatment by CD138 antigen targeting with bismuth-213 and Melphalan. Nucl Med Biol 2014;41 Suppl:e30. [DOI] [PubMed] [Google Scholar]
  • 73. Beck R, Seidl C, Pfost B, et al. 213Bi-radioimmunotherapy defeats early-stage disseminated gastric cancer in nude mice. Cancer Sci 98:1215 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 74. Norenberg JP, Krenning BJ, Konings IR, et al. 213Bi-[DOTA, Tyr3]octreotide peptide receptor radionuclide therapy of pancreatic tumors in a preclinical animal model. Clin Cancer Res 2006;12(3 Pt 1):897. [DOI] [PubMed] [Google Scholar]
  • 75. Qu CF, Songl YJ, Rizi SM, et al. In vivo and in vitro inhibition of pancreatic cancer growth by targeted alpha therapy using 213Bi-CHX.A”-C595. Cancer Biol Ther 2005;4:848. [DOI] [PubMed] [Google Scholar]
  • 76. Allen BJ, Tian Z, Rizvi SM, et al. Preclinical studies of targeted alpha therapy for breast cancer using 213Bi-labelled-plasminogen activator inhibitor type 2. Br J Cancer 2003;88:944. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 77. Stutchbury TK, Al-Ejeh F, Stillfried GE, et al. Preclinical evaluation of 213Bi-labeled plasminogen activator inhibitor type 2 in an orthotopic murine xenogenic model of human breast carcinoma. Mol Cancer Ther 2007;6:203. [DOI] [PubMed] [Google Scholar]
  • 78. Song H, Shahverdi K, Huso DL, et al. 213Bi (alpha-emitter)-antibody targeting of breast cancer metastases in the neu-N transgenic mouse model. Cancer Res 2008;68:3873. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 79. Kelly MP, Lee FT, Tahtis K, et al. radioimmunotherapy with alpha-particle emitting 213Bi-C-functionalized trans-cyclohexyl-diethylenetriaminepentaacetic acid-humanized 3S193 is enhanced by combination with paclitaxel chemotherapy. Clin Cancer Res 2007;13(18 Pt 2):5640s. [DOI] [PubMed] [Google Scholar]
  • 80. Zhang DY, Li Y, Rizvi SM, et al. Cytotoxicity of breast cancer cells overexpressing HER2/neu by 213Bi-Herceptin radioimmunoconjugate. Cancer Lett 2005;218:181. [DOI] [PubMed] [Google Scholar]
  • 81. Michel RB, Rosario AV, Brechbiel MW, et al. Experimental therapy disseminated B-cell lymphoma xenografts with 213Bi-labeled anti-CD74. Nucl Med Biol 2003;30:715. [DOI] [PubMed] [Google Scholar]
  • 82. Friessen C, Glatting G, Koop B, et al. Breaking chemoresistance and radioresistance with [213Bi]anti-CD45 antibodies in leukemia cells. Cancer Res 2007;67:1950. [DOI] [PubMed] [Google Scholar]
  • 83. Kennel SJ, Boll R, Stabin M, et al. Radioimmunotherapy of micrometastases in lung with vascular targeted 213Bi. Br J Cancer 1999;80:175. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 84. Gustafsson-Lutz A, Back T, Aneheim E, et al. Therapeutic efficacy of α-radioimmunotherapy with different activity levels of the 213Bi-labled monoclonal antibody MX35 in an ovarian cancer model. EJNMMI Res 2017;7:38. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 85. Vallon M, Seidl C, Blechert B, et al. Enhanced efficacy of combined 213Bi-DTPA-F3 and paclitaxel therapy of peritoneal carcinomatosis is mediated by enhanced induction of apoptosis and G2/M phase arrest. Eur J Nucl Med Mol Imaging 2012;39:1886. [DOI] [PubMed] [Google Scholar]
  • 86. Lingappa M, Song H, Thompson S, et al. Immunoliposomal delivery of 213Bi for alpha-emitter targeting of metastatic breast cancer. Cancer Res 2010;70:681. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 87. Wulbrandt C, Seidl C, Gaetner FC, et al. Alpha-emitting 213Bi-anti-EGFR immunoconjugates eradicates tumor cells independent of oxygenation. PLoS One 2013;8:e64730. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 88. Krolicki L, Bruchertseifer F, Kunikowska J, et al. Prolonged survival in secondary globlastoma following local injection of targeted alpha therapy with 213Bi-substance P analogue. Eur J Nucl Med Mol Imaging 2018;45:1636. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 89. Krolicki L, Buchertsifer F, Kunikowska J, et al. Safety and efficacy of targeted alpha therapy with 213Bi-DOTA-subtance P in recurrent glioblastoma. Eur J Nucl Med Mol Imaging 2019;46:614. [DOI] [PubMed] [Google Scholar]
  • 90. Cordier D, Forrer F, Bruchertseifer F, et al. Targeted alpha-radionuclide therapy of functionally critically located gliomas with 213Bi-DOTA-[Thi8,Met(O2)11]-substance P: A pilot trial. Eur J Nucl Med Mole Imaging 2010;37:1335. [DOI] [PubMed] [Google Scholar]
  • 91. Cordier D, Merlo A. Long-term results of targeted low-grade glioma treatment with 213Bi-DOTA-[Thi8, Met(O2)11]-substance P. Cancer Biother Radiopharm 2019;34:413. [DOI] [PubMed] [Google Scholar]
  • 92. Pfost B, Seidl C, Autenrieth M, et al. Intravesical alpha-radioimunotherapy with 213Bi-anti-EGFR-mAb defeats human bladder carcinoma in xenografted nude mice. J Nucl Med 2009;50:1700. [DOI] [PubMed] [Google Scholar]
  • 93. Autenrieth ME, Seidl C, Bruchertseifer F, et al. Treatment of carcinoma in situ of the urinary bladder with an alpha-emitter immunoconjugate targeting the epidermal growth factor reporter: A pilot study. Eur J Nucl Med Mol Imaging 2018;45:1364. [DOI] [PubMed] [Google Scholar]
  • 94. Allen BJ, Raja C, Rizvi S, et al. Intralesional targeted alpha therapy for metastatic melanoma. Cancer Biol Ther 2005;4:1318. [DOI] [PubMed] [Google Scholar]
  • 95. Sathekge M, Knoesen O, Meckel M, et al. 213Bi-PSMA-617 targeted alpha-radionuclide therapy in metastatic castration-resistant prostate cancer. Eur J Nucl Med Mol Imaging 2017;44:1099. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 96. Zalutsky MR, Pruszynski M. Astatine-211: Production and availability. Curr Radiopharm 2011;4:177. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 97. Vaidyanathan G, Zalutsky M. Applications of 211At and 223Ra in targeted alpha-particle radiotherapy. Curr Radiopharm 2011;4:283. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 98. Kennel SJ, Mirzadeh S, Eckelman WC, et al. Vascular-targeted radioimmunotherapy with the alpha-particle emitter 211At. Radiat Res 2002;157:663. [DOI] [PubMed] [Google Scholar]
  • 99. Zhang M, Yao Z, Xhang Z, et al. The anti-CD25 monoclonal antibody 7G7/B6, armed with the alpha-emitter 211At, provides effective radioimmunotherapy for a murine model of leukemia. Cancer Res 2006;66:8227. [DOI] [PubMed] [Google Scholar]
  • 100. Link EM, Carpenter RN, Hansen G. [211At]methylene blue for targeted radiotherapy of human melanoma xenografts: Dose fractionation in the treatment of cutaneous tumors. Eur J Cancer 1996;32A:1240. [DOI] [PubMed] [Google Scholar]
  • 101. Vergote I, Larsen RH, de Vos L, et al. Therapeutic efficacy of the alpha emitter 211At bound on microspheres compared with 90Y and 32P colloids in a murine intraperitoneal tumor model. Gynecol Oncol 1992;47:366. [DOI] [PubMed] [Google Scholar]
  • 102. Watabe T, Kaneda-Nakashima K, Liu Y, et al. Enhancement of 211At uptake via the sodium iodide symporter by the addition of ascorbic acid in targeted α-therapy of thyroid cancer. J Nucl Med 2019;60:1301. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 103. Hallqvist A, BergmarkK, Back TA, et al. Intraperitoneal alpha-emitting radio immunotherapy with astatine-211 relapsed ovarian cancer: Long term follow-up with individual absorbed dose estimations. J Nucl Med 2019;60:1073. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 104. Hagemann UB, Ellingsen C, Schuhmacher J, et al. Mesothelin-targeted thorium-227 conjugate (MSLN-TTC): Preclinical evaluation of a new targeted alpha therapy for mesothelin-positive cancers. Clin Cancer Res 2019;25:4723. [DOI] [PubMed] [Google Scholar]
  • 105. Wickstroem K, Hagemann UB, Cruciani V, et al. Synergistic effect of a mesothelin-targeted 227Th conjugate in combination with DNA damage inhibitors in ovarian cancer xenograft models. J Nucl Med 2019;60:1293. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 106. Heyerdahl H, Abbas N, Sponheim K, et al. Targeted alpha therapy with 227Th-trastuzumab of intraperitoneal ovarian cancer in nude mice. Curr Radiopharm 2013;6:106. [DOI] [PubMed] [Google Scholar]
  • 107. Hammer S, Hagemann UB, Zitzmann-Kolbe S, et al. Preclinical efficacy of a PSMA-targeted thorium-227 conjugate (PSMA-TTC), a targeted alpha therapy for prostate cancer. Clin Cancer Res 2019. [Epub ahead of print]; DOI: 10.1158/1078-0432.CCR-19-2268 [DOI] [PubMed]
  • 108. Wickstroem K, Karlsson J, Ellingsen C, et al. Synergistic effect of a HER2 targeted thorium-227 conjugate in combination with olaparib in a BRCA2 deficient xenograft model. Pharmaceuticals (Basel) 2019;12:Pii: [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 109. Wickstroem K, Hagemann UB, Kristian A, et al. Preclinical combination studies of an FGFR2 targeted thorium-227 conjugate and the ATR inhibitor BAY 1895344. Int J Radiat Oncol Biol Phys 2019;105:410. [DOI] [PubMed] [Google Scholar]
  • 110. Hagemann UB, Wickstroem K, Wang E, et al. In vitro and in vivo efficacy of a novel CD33-tarheted thorium-227 conjugate for the treatment of acute myeloid leukemia. Mol Cancer Ther 2016;15:2422. [DOI] [PubMed] [Google Scholar]
  • 111. Yong K, Brechbiel MW. Application of 212Pb for targeted α-particle therapy (TAT): Pre-clinical and mechanistic understanding through to clinical translation. AIMS Med Sci 2015;2:228. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 112. Yong K, Brechbiel MW. Towards translation of 212Pb as a clinical therapeutic; getting the lead in! Dalton Trans 2011;40:6068 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 113. Banerjee SR, Minn I, Kumar V, et al. Preclinical evaluation of 203/212Pb-labeled low-molecular weight compounds for targeted radiopharmaceutical therapy of prostate cancer. J Nucl Med 2020;61:80. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 114. Dos Santos JC, Schafer M, Bauder-Wust U, et al. Development and dosimetry of 203Pb/212Pb-labeled PSMA ligands: Bringing the lead into PSMA-targeted alpha therapy. Eur J Nucl Med Mol Imaging 2019;46:1081. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 115. Corroyer-Dulmont A, Valable S, Falzone N, et al. VCAM-1 targeted alpha-particle therapy for early brain metastases. Neuro Oncol 2019. [Epub ahead of print]; DOI: 10.1093/neuonc/noz169 [DOI] [PMC free article] [PubMed]
  • 116. Stallons TAR, Saidi A, Tworowska I, et al. Preclinical investigation of 212Pb-DOTAMTATE for peptide receptor radionuclide therapy in neuroendocrine tumor model. Mol Cancer Ther 2019;18:1012. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 117. Kasten BB, Oliver PG, Kim H, et al. 212Pb-labeled antibody 225.28 targeted to chondroitin sulfate proteoglycans 4 for triple negative breast cancer therapy in mouse models. Int J Mol Sci 2018;19:Pii: [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 118. Kasten BB, Gangrade A, Kim H, et al. 212Pb-labeled B7-H3-targeting antibody for pancreatic cancer therapy in mouse models. Nucl Med Biol 2018;58:67. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 119. Kasten BB, Arend RC, Katre AA, et al. B7-H3-targeted 212Pb radioimmunotherapy of ovarian cancer in preclinical models. Nucl Med Biol 2017;47:23. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 120. Milenic DE, Baidoo KE, Kim YS, et al. Evaluation of cetuximab as a candidate for targeted α-particle radiation therapy of HER1-positive disseminated intraperitoneal disease. MABs 2015;7:255. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 121. Meredith RF, Torgue JJ, Rozgaja TA, et al. Safety and outcome measures of first-in-human intraperitoneal α immunotherapy with 212Pb-TCMC-trastuzumab. Am J Clin Oncol 2018;4:716. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 122. Meredith RF, Torgue J, Shen S, et al. Dose escalation and dosimetry of first-in-human α radioimmunothrerapy with 212Pb-TCMC-trastuzumab. J Nucl Med 2014;55:1638. [DOI] [PMC free article] [PubMed] [Google Scholar]

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