Separation of Yb as YbSO4 from the 176Yb target for production of 177Lu via the 176Yb(n, γ)177Yb→177Lu process

A multi-stage COF membrane column system for enhanced Yb/Lu separation

This study introduces an innovative multi-stage membrane column separation system that combines membrane and column separation technologies, utilizing a COF membrane as the packing material. This approach achieves a superior separation factor and a reduced elution volume for Yb3+/Lu3+ separation, offering a new approach to address challenges in column separation.

Preparation and Biodistribution Assessment of 177Lu-curcumin as a Possible Therapeutic Agent

Purpose

Curcumin as a potent anti-inflammatory and cancer-prevention molecule was labeled with n.c.a 177Lu. The combination of 177Lu as a theranostic agent and curcumin as an anti-cancer can be considered for nuclear medicine.

Methods

First, n.c.a 177Lu (specific activity = 48 Ci/mg) was prepared using the extraction chromatography method. Then, semi-empirical quantum chemical calculations were applied to get a deeper insight into the complexation reaction between Lu+ 3 and curcumin ligand. UV-Vis spectrophotometry was used for the determination of the metal-to-curcumin ratio. Subsequently, a mixture of (111-333 MBq) n.c.a 177Lu, 50 µL curcumin solution in ethanol, and 450 µL acetate buffer at pH = 5 was incubated for 1 h at 95 ºC. The Lu-curcumin complex chemical structure was characterized using IR spectroscopy. Finally, the prepared complex was analyzed by different quality control tests.

Results

Complexometry using UV-Vis studies showed a 1:2 ratio for Lutetium: curcumin complex which is in agreement with theoretical calculations. The IR-spectra analysis also confirmed the complex formation. The radiochemical purity of n.c.a 177Lu -curcumin was more than 95% as determined by radio-TLC. The stability of up to 48 h was observed for the prepared complex in serum. The partition coefficient was calculated for the compound (log P = -0.31). Evaluating biodistribution in tumoral mice exhibited high tumor uptake (%ID/gtissue = 2.03).

Conclusion

The promising results showed that n.c.a 177Lu-curcumin can be considered as a possible radiopharmaceutical agent for therapeutic applications.

Synthesis and Characterization of Divalent Samarium and Thulium N,N-Dimethylaminodiboranates

The syntheses and molecular structures of new Sm^II and Tm^II N,N-dimethylaminodiboranate (DMADB) complexes are described. Treating SmI₂(THF)₂ with Na(H₃BNMe₂BH₃) in THF results in the formation of Sm(H₃BNMe₂BH₃)₂(THF)₃ (1), which can be readily converted to Sm(H₃BNMe₂BH₃)₂(DME)₂ (DME = 1,2-dimethoxyethane) or Sm(H₃BNMe₂BH₃)₂(diglyme) by exchange with the corresponding ether. We also show that Sm(H₃BNMe₂BH₃)₂(THF)₃ can be prepared by reduction of the Sm^III compound Sm(H₃BNMe₂BH₃)₃(THF) with KC₈ and that addition of 18-crown-6 to this reaction mixture results in the formation of the Sm^II compound Sm(H₃BNMe₂BH₃)₂(18-crown-6). In a similar fashion, two new Tm^II complexes have been synthesized: treatment of TmI₂ in THF with Na(H₃BNMe₂BH₃) results in the formation of Tm(H₃BNMe₂BH₃)₂(THF)₂ and Tm(H₃BNMe₂BH₃)₂(THF)₃, which form a cocrystal. IR data and elemental analyses are reported for all the new compounds, as are their crystal structures. ¹H and ¹¹B NMR data are provided where available.

Investigation of radiolabeling efficacy by enhancement of the chemical form of no carrier added 177Lu isolated by electro amalgamation process

BACKGROUND

Due to the suitable nuclear decay characteristics, 177Lu is an attractive radionuclide for various therapeutic applications. The non-carrier added form of 177Lu has drawn many attention because of its high specific activity needed in radiolabeling studies. There have been several separation methods for NCA 177Lu production.

OBJECTIVES

Among the various separation methods, the electro-amalgamation separation method has got a large potential for large scale production. Li presence is a significant problem in this separation method, which seriously affects the radiolabeling efficiency.

METHOD

In this study, Li was separated from the final product of electro-amalgamation separation by adding an ion-exchange chromatography column to the separation process.

RESULTS

NCA 177Lu was obtained by 84.09% ELM separation yield, 99.9% radionuclide purity and, 65 Ci/g specific activity. Then, 177Lu (177LuCl3 chemical form) was separated from Li using the ion exchange chromatography method by a separation yield of 94%. The obtained results of the radiolabeling efficacy studies showed that the radiochemical purity and radio-complex stability were significantly increased by separating of NCA 177Lu from Li.

CONCLUSION

This new separation setup consisting of two steps allows using 177Lu of such a favorable quality for labeling studies.

Radioactive Main Group and Rare Earth Metals for Imaging and Therapy

Radiometals possess an exceptional breadth of decay properties and have been applied to medicine with great success for several decades. The majority of current clinical use involves diagnostic procedures, which use either positron-emission tomography (PET) or single-photon imaging to detect anatomic abnormalities that are difficult to visualize using conventional imaging techniques (e.g., MRI and X-ray). The potential of therapeutic radiometals has more recently been realized and relies on ionizing radiation to induce irreversible DNA damage, resulting in cell death. In both cases, radiopharmaceutical development has been largely geared toward the field of oncology; thus, selective tumor targeting is often essential for efficacious drug use. To this end, the rational design of four-component radiopharmaceuticals has become popularized. This Review introduces fundamental concepts of drug design and applications, with particular emphasis on bifunctional chelators (BFCs), which ensure secure consolidation of the radiometal and targeting vector and are integral for optimal drug performance. Also presented are detailed accounts of production, chelation chemistry, and biological use of selected main group and rare earth radiometals.

Chemical aspects of metal ion chelation in the synthesis and application antibody-based radiotracers

Radiometals are becoming increasingly accessible and are utilized frequently in the design of radiotracers for imaging and therapy. Nuclear properties ranging from the emission of γ-rays and β+ -particles (imaging) to Auger electron and β- and α-particles (therapy) in combination with long half-lives are ideally matched with the relatively long biological half-life of monoclonal antibodies in vivo. Radiometal labeling of antibodies requires the incorporation of a metal chelate onto the monoclonal antibody. This chelate must coordinate the metal under mild conditions required for the handling of antibodies, as well as provide high kinetic, thermodynamic, and metabolic stability once the metal ion is coordinated to prevent release of the radionuclide before the target site is reached in vivo. Herein, we review the role of different radiometals that have found applications of the design of radiolabeled antibodies for imaging and radioimmunotherapy. Each radionuclide is described regarding its nuclear synthesis, coordinative preference, and radiolabeling properties with commonly used and novel chelates, as well as examples of their preclinical and clinical applications. An overview of recent trends in antibody-based radiopharmaceuticals is provided to spur continued development of the chemistry and application of radiometals for imaging and therapy.

Feasibility study for production and quality control of Yb-175 as a byproduct of no carrier added Lu-177 preparation for radiolabeling of DOTMP

Skeletal uptake of β^- emitters of DOTMP complexes is used for the bone pain palliation. In this study, two moderate energy β^- emitters, ¹⁷⁷Lu (T_1/2 = 6.7 days, E_βmax = 497 keV) and ¹⁷⁵Yb (T_1/2 = 4.2 days, E_βmax = 480 keV), are considered as potential agents for the development of the bone-seeking radiopharmaceuticals. Since the specific activity of the radiolabelled carrier molecules should be high, the non-carrier-added (NCA) radionuclides have an effective role in nuclear medicine. Many researchers have presented the synthesis of NCA ¹⁷⁷Lu. Among these separation techniques, extraction chromatography has been considered more capable than other methods. In this study, a new approach, in addition to production of NCA ¹⁷⁷Lu by EXC procedure is using pure ¹⁷⁵Yb that was usually considered as a waste material in this method but because of high radionuclidic purity of ¹⁷⁵Yb produced by this method we used it for radiolabeling as well as NCA ¹⁷⁷Lu. To obtain optimum conditions, some effective factors on separation of Lu/Yb by EXC were investigated. The NCA ¹⁷⁷Lu and pure ¹⁷⁵Yb were produced with radionuclidic purity of 99.99 and 99.97% respectively by irradiation of enriched ¹⁷⁶Yb target in thermal neutron flux of 5 × 10¹³ n/cm² s for 14 days. ¹⁷⁷Lu-DOTMP and ¹⁷⁵Yb-DOTMP were obtained with high radiochemical purities (> 95%) under optimized reaction conditions. Two radiolabeled complexes exhibited excellent stability at room temperature. Biodistribution studies in rats showed favorable selective skeletal uptake with rapid clearance from blood along with insignificant accumulation of activity in other non-target organs for two radiolabelled complexes.

Production and quality control 177Lu (NCA)-DOTMP as a potential agent for bone pain palliation

Skeletal uptake of radiolabeled-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetramethylene phosphoric acid (e.g., 177Lu-DOTMP) complex, is used for bone pain palliation. The moderate energy of β-emitting 177Lu (T½ = 6.7 d, Eβmax = 497keV) has been considered as a potential radionuclide for development of the bone-seeking radiopharmaceutical. Since the specific activity of the radiolabeled carrier molecules should be high, the "no-carrier-added radionuclides" have sig-nificant roles in nuclear medicine. Many researchers illustrated no-carrier-added 177Lu production; among these separation techniques such as ion exchange chromatography, reversed phase ion-pair, and electrochemical method, extraction chromatography has been considered more capable than other methods. In order to optimize the conditions, some effective factors on separation of Lu/Yb were investigated by EXC. The NCA 177Lu, produced by this method, was mixed with 300 μl of DOTMP solution (20 mg in 1 mL of 0.5 M NaHCO3, pH = 8) and incu-bated under stirring at room temperature for 45 min. Radiochemical purity of the 177Lu-DOTMP complex was determined using radio-thin-layer chromatography (RTLC) method. The complex was injected to wild-type rats and biodistribution was then studied for seven days. The NCA 177Lu was produced with specific activ-ity of 48 Ci/mg and with a radinuclidic purity of 99.99% through irradiation of enriched 176Yb target (1 mg) in a thermal neutron flux of 4 × 1013 n.cm-2.s-1 for 14 days. 177Lu-DOTMP was obtained with high radiochemical purities (> 98%) under optimized reaction conditions. The radiolabeled complex exhibited excellent stability at room temperature. Biodistribution of the radiolabeled complex studies in rats showed favorable selective skeletal uptake with rapid clearance from blood along with insignificant accumulation within the other nontargeted organs.

Peptide receptor radionuclide therapy: an overview

Peptide receptor radionuclide therapy (PRRT) is a site-directed targeted therapeutic strategy that specifically uses radiolabeled peptides as biological targeting vectors designed to deliver cytotoxic levels of radiation dose to cancer cells, which overexpress specific receptors. Interest in PRRT has steadily grown because of the advantages of targeting cellular receptors in vivo with high sensitivity as well as specificity and treatment at the molecular level. Recent advances in molecular biology have not only stimulated advances in PRRT in a sustainable manner but have also pushed the field significantly forward to several unexplored possibilities. Recent decades have witnessed unprecedented endeavors for developing radiolabeled receptor-binding somatostatin analogs for the treatment of neuroendocrine tumors, which have played an important role in the evolution of PRRT and paved the way for the development of other receptor-targeting peptides. Several peptides targeting a variety of receptors have been identified, demonstrating their potential to catalyze breakthroughs in PRRT. In this review, the authors discuss several of these peptides and their analogs with regard to their applications and potential in radionuclide therapy. The advancement in the availability of combinatorial peptide libraries for peptide designing and screening provides the capability of regulating immunogenicity and chemical manipulability. Moreover, the availability of a wide range of bifunctional chelating agents opens up the scope of convenient radiolabeling. For these reasons, it would be possible to envision a future where the scope of PRRT can be tailored for patient-specific application. While PRRT lies at the interface between many disciplines, this technology is inextricably linked to the availability of the therapeutic radionuclides of required quality and activity levels and hence their production is also reviewed.

Production of (177)Lu for Targeted Radionuclide Therapy: Available Options

BACKGROUND

This review provides a comprehensive summary of the production of (177)Lu to meet expected future research and clinical demands. Availability of options represents the cornerstone for sustainable growth for the routine production of adequate activity levels of (177)Lu having the required quality for preparation of a variety of (177)Lu-labeled radiopharmaceuticals. The tremendous prospects associated with production of (177)Lu for use in targeted radionuclide therapy (TRT) dictate that a holistic consideration should evaluate all governing factors that determine its success.

METHODS

While both "direct" and "indirect" reactor production routes offer the possibility for sustainable (177)Lu availability, there are several issues and challenges that must be considered to realize the full potential of these production strategies.

RESULTS

This article presents a mini review on the latest developments, current status, key challenges and possibilities for the near future.

CONCLUSION

A broad understanding and discussion of the issues associated with (177)Lu production and processing approaches would not only ensure sustained growth and future expansion for the availability and use of (177)Lu-labeled radiopharmaceuticals, but also help future developments.

Stability of 47Sc-complexes with acyclic polyamino-polycarboxylate ligands

The aim of this study was to evaluate acyclic ligands which can be applied for labeling proteins such as monoclonal antibodies and their fragments with scandium radionuclides. Recently, scandium isotopes (⁴⁷Sc, ⁴⁴Sc) are more available and their properties are convenient for radiotherapy or PET imaging. They can be used together as “matched pair” in theranostic approach. Because proteins denaturize at temperature above 42 °C, ligands which efficiently form complexes at room temperature, are necessary for labelling such biomolecules. For complexation of scandium radionuclides open chain ligands DTPA, HBED, BAPTA, EGTA, TTHA and deferoxamine have been chosen. We found that the ligands studied (except HBED) form strong complexes within 10 min and that the radiolabelling yield varies between 96 and 99 %. The complexes were stable in isotonic NaCl, but stability of ⁴⁶Sc-TTHA, ⁴⁶Sc-BAPTA and ⁴⁶Sc-HBED in PBS buffer was low, due to formation by Sc³⁺stronger complexes with phosphates than with the studied ligands. From the radiolabelling studies with n.c.a. ⁴⁷Sc we can conclude that the most stable complexes are formed by the 8-dentate DTPA and EGTA ligands.

An electro-amalgamation approach to produce 175Yb suitable for radiopharmaceutical applications

175Yb is a prospective reactor produced radionuclide suitable for preparation of therapeutic radiopharmaceuticals. However, a major restraint in the use of 175Yb produced via the (n, γ) reaction, for therapeutic applications, is the presence of longer-lived 177Lu impurity which is co-produced along with 175Yb on irradiation of natural Yb2O3 target. A radiochemical separation procedure adopting electro-amalgamation approach for the removal of 177Lu impurity from 175Yb has been critically evaluated. The experimental parameters such as applied potential, electrolysis time and the pH of the electrolyte, affecting the electrochemical separation process, were studied and optimized. The developed radiochemical procedure was extensively tested for purification of up to 15 GBq of 175Yb. The purified 175Yb could be obtained in HCl medium with ∼95% yield. The 177Lu impurity could not be detected in the purified product and 175Yb was found suitable for the preparation of potential radiotherapeutic agents.

Macrocyclic complexes of scandium radionuclides as precursors for diagnostic and therapeutic radiopharmaceuticals

The aim of this study was to evaluate new ligands which can be applied for labeling biomolecules with scandium radionuclides. Two radionuclides of scandium, (47)Sc and (44)Sc, are perspective radioisotopes for radiotherapy and diagnostic imaging. (47)Sc decays with a half-life of 3.35 days and a maximum β(-) energy of 600 keV and could be an alternative to carrier added (177)Lu radionuclide for targeted radionuclide therapy. Another scandium radionuclide (44)Sc (t(1/2) = 3.92 h) is an ideal β(+) emitter for PET diagnosis. It can be obtained as a daughter of the long-lived (44)Ti (t(1/2) = 60.4 y) from (44)Ti/(44)Sc generator. For complexation of scandium radionuclides macrocyclic ligands having a cavity size similar to Sc(3+) ionic radius were selected: 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), 1,4,7-triazacyclononane-1,4,7 triacetic acid (NOTA), 1,4,7-triazacyclodecane-1,4,7 triacetic acid and 1,4,7-triazacycloundecane triacetic acid, and analogs of NOTA with 10, 11 and 12 atoms of the carbon in the ring. Our results have shown that from the studied macrocyclic ligands studied DOTA is most efficient for binding scandium radionuclides (44)Sc and (47)Sc to biomolecules. The determined stability constant of Sc-DOTA complex logK = 27.0 is comparable with stability constants for Y(3+) and heaviest lanthanides but is higher than those for In(3+) and Ga(3+). Also (46)Sc-DOTATATE conjugate exhibits high stability in-vitro studies. The (13)C NMR studies have shown that Sc-DOTA like Lu-DOTA forms in solution complexes with eight-coordination geometry. The lipophilicity of Sc-DOTATATE is nearly identical to that of Lu-DOTATATE, which suggests similar receptor affinity of both radioconjugates.