Targeting Breast Cancer Using 177 Lu-Labeled Trastuzumab and Trastuzumab Fragment : First-in-Human Clinical Experience

PURPOSE

A monoclonal antibody, trastuzumab, is used for immunotherapy for HER2-expressing breast cancers. Large-sized antibodies demonstrate hepatobiliary clearance and slower pharmacokinetics. A trastuzumab fragment (Fab; 45 kDa) has been generated for theranostic use.

PATIENTS AND METHODS

Fab was generated by papain digestion. Trastuzumab and Fab have been radiolabelled with 177 Lu after being conjugated with a bifunctional chelating. The affinity and target specificity were studied in vitro. The first-in-human study was performed.

RESULTS

The bifunctional chelating agent conjugation of 1-2 molecules with trastuzumab and Fab was detected at the molar ratio 1:10 in bicarbonate buffer (0.5 M, pH 8) at 37°-40°C. However, 2-3 molecules of bifunctional chelating agent were conjugated when DMSO in PBS (0.1 M, pH 7) was used as a conjugation buffer at a molar ratio of 1:10. The radiolabelling yield of DOTA-conjugated Fab and trastuzumab at pH 5, 45°C to 50°C, with incubation time 2.5-3 hours was 80% and 41.67%, respectively. However, with DOTAGA-conjugated trastuzumab and Fab, the maximum radiolabelling yield at pH 5.5, 37°C, and at 2.5-3 hours was 80.83% and 83%, respectively. The calculated K d of DOTAGA Fab and trastuzumab with HER2-positive SKBR3 cells was 6.85 ± 0.24 × 10 -8 M and 1.71 ± 0.10 × 10 -8 M, respectively. DOTAGA-Fab and trastuzumab showed better radiolabelling yield at mild reaction conditions.177 Lu-DOTAGA-Fab demonstrated higher lesion uptake and lower liver retention as compared with 177 Lu-DOTAGA-trastuzumab. However, 177 Lu-DOTAGA-Fab as compared with 177 Lu-DOTAGA-trastuzumab showed a relatively early washout (5 days) from the lesion.

CONCLUSIONS

177 Lu-DOTAGA-Fab and trastuzumab are suitable for targeting the HER2 receptors.

Brachytherapy at the nanoscale with protein functionalized and intrinsically radiolabeled [169Yb]Yb2O3 nanoseeds

PURPOSE

Classical brachytherapy of solid malignant tumors is an invasive procedure which often results in an uneven dose distribution, while requiring surgical removal of sealed radioactive seed sources after a certain period of time. To circumvent these issues, we report the synthesis of intrinsically radiolabeled and gum Arabic glycoprotein functionalized [169Yb]Yb2O3 nanoseeds as a novel nanoscale brachytherapy agent, which could directly be administered via intratumoral injection for tumor therapy.

METHODS

169Yb (T½ = 32 days) was produced by neutron irradiation of enriched (15.2% in 168Yb) Yb2O3 target in a nuclear reactor, radiochemically converted to [169Yb]YbCl3 and used for nanoparticle (NP) synthesis. Intrinsically radiolabeled NP were synthesized by controlled hydrolysis of Yb3+ ions in gum Arabic glycoprotein medium. In vivo SPECT/CT imaging, autoradiography, and biodistribution studies were performed after intratumoral injection of radiolabeled NP in B16F10 tumor bearing C57BL/6 mice. Systematic tumor regression studies and histopathological analyses were performed to demonstrate therapeutic efficacy in the same mice model.

RESULTS

The nanoformulation was a clear solution having high colloidal and radiochemical stability. Uniform distribution and retention of the radiolabeled nanoformulation in the tumor mass were observed via SPECT/CT imaging and autoradiography studies. In a tumor regression study, tumor growth was significantly arrested with different doses of radiolabeled NP compared to the control and the best treatment effect was observed with ~ 27.8 MBq dose. In histopathological analysis, loss of mitotic cells was apparent in tumor tissue of treated groups, whereas no significant damage in kidney, lungs, and liver tissue morphology was observed.

CONCLUSIONS

These results hold promise for nanoscale brachytherapy to become a clinically practical treatment modality for unresectable solid cancers.

Normal physiological distribution and tumor localization of 64 CuCl 2 in different human malignancies along with semiquantitative scoring: a comparative evaluation with 18 Fluorodeoxyglucose ( 18 FDG) PET-CT

OBJECTIVE

This study aimed to explore 64-Copper-Chloride ( 64 CuCl 2 ) PET-CT in various malignancies and demonstrate a head-to-head comparison of uptake on 64 CuCl 2 PET/computed tomography (CT) and 18 fluorodeoxyglucose ( 18 FDG)-PET/CT scans for different malignancies, with an emphasis on 18 FDG nonavid malignancies.

METHODS

Fifty-three patients diagnosed with various biopsy-proven malignancies (except prostate cancer) were recruited in this prospective study. All the patients underwent both 64 CuCl 2 PET/CT and 18 FDG-PET/CT. 64 CuCl 2 PET/CT was acquired at 1, 3 and 24 h time points. We studied the physiological biodistribution of 64 CuCl 2 in the various organs, corroborated the uptake of 64 CuCl 2 with various types of malignancies and comparison of their uptake with 18 FDG-PET/CT and their correlation with each other in various lesions.

RESULTS

The biodistribution study showed that the liver concentrated 64 CuCl 2 the most out of all the organs, followed by the pancreas and large intestine. Liver and intestinal activity increased subsequently with delayed imaging, and the washout of 64 CuCl 2 was noted in the pancreas in delayed images and followed a hepatobiliary excretion of tracer over a period of time. In lesion-wise analysis, it was noted that the primary neuroendocrine tumor, melanoma and renal/urothelial malignancy group showed more uptake of 64 CuCl 2 , than that in metastasis and vice-versa was noted in lung and soft tissue malignancies. Comparing it with 18 FDG, it was seen that FDG showed more uptake in lesions and showed no significant correlation (Kappa value: 0.089) with the uptake of 64 CuCl 2 in the lesion-wise comparison.

CONCLUSION

64 CuCl 2 PET/CT did not show any added advantage over 18 FDG-PET/CT in the evaluation of the studied malignancies, both primary and their metastasis. Biodistribution studies showed the liver as the organ with maximum uptake, which implies it may hinder the detection of abdominal or hepatic involvement of the disease.

Synthesis, Quality Control, and Bench-to-Bed Translation of a New [68Ga]Ga-Labeled NOTA-Conjugated Bisphosphonate for Imaging Skeletal Metastases by Positron Emission Tomography

Background: Early detection of skeletal metastasis is of great interest to determine the prognosis of cancer. Positron emission tomography-computed tomography (PET-CT) imaging provides a better temporal and spectral resolution than single photon emission computed tomography-computed tomography (SPECT-CT) imaging, and hence is more suitable to detect small metastatic lesions. Although [18F]NaF has been approved by U.S. FDA for a similar purpose, requirement of a medical cyclotron for its regular formulation restricts its extensive utilization. Efforts have been made to find suitable alternative molecules that can be labeled with 68Ga and used in PET-CT imaging. Objective: The main objective of this study is to synthesize and evaluate a new [68Ga]Ga-labeled NOTA-conjugated geminal bisphosphonate for its potential use in early detection of skeletal metastases using PET-CT. Methods: The authors performed a multistep synthesis of a new NOTA-conjugated bisphosphonic acid using thiourea linker and radiolabeled the molecule with 68Ga. The radiolabeled formulation was evaluated for its in vitro stability, affinity for hydroxyapatite (HA) particles, preclinical biodistribution in animal models, and PET-CT imaging in patients. Results: The bifunctional chelator (NOTA)-conjugated bisphosphonate was synthesized with 97.8% purity and radiolabeled with 68Ga in high yield (>98%). The radiolabeled formulation was found to retain its stability in vitro to the extent of >95% up to 4 h in physiological saline and human serum. The formulation also showed high affinity for HA particles in vitro with Kd = 907 ± 14 mL/g. Preclinical biodistribution studies in normal Wistar rats demonstrated rapid and almost exclusive skeletal accumulation of the complex. PET-CT imaging in a patient confirmed its ability to detect small metastatic skeletal lesions. Conclusions: The newly synthesized [68Ga]Ga-labeled NOTA-conjugated bisphosphonate is a promising radiotracer for PET-CT imaging for skeletal metastases.

[90Y]Yttria Alumino Silicate Glass Microspheres: A Biosimilar Formulation to "TheraSphere" for Cost-Effective Treatment of Liver Cancer

Background: Selective internal radiation therapy (SIRT) using a suitable β--emitting radionuclide is a promising treatment modality for unresectable liver carcinoma. Yttrium-90 (90Y) [T1/2 = 64.2 h, Eβ(max) = 2.28 MeV, no detectable γ-photon] is the most preferred radioisotope for SIRT owing to its favorable decay characteristics. Objective: The present study describes indigenous development and evaluation of intrinsically radiolabeled [90Y]yttria alumino silicate ([90Y]YAS) glass microsphere, a formulation biosimilar to "TheraSphere" (commercially available, U.S. FDA-approved formulation), for SIRT of unresectable liver carcinoma in human patients. Methods: YAS glass microspheres of composition 40Y2O3-20Al2O3-40SiO2 (w/w) and diameter ranging between 20 and 36 μm were synthesized with almost 100% conversion efficiency and >99% sphericity. Intrinsically labeled [90Y]YAS glass microspheres were produced by thermal neutron irradiation of cold YAS glass microspheres in a research reactor. Subsequent to in vitro evaluations and in vivo studies in healthy Wistar rats, customized doses of [90Y]YAS glass microspheres were administered in human patients. Results: [90Y]YAS glass microspheres were produced with 137.7 ± 8.6 MBq/mg YAS glass (∼6800 Bq per microsphere) specific activity and 99.94% ± 0.02% radionuclidic purity at the end of irradiation. The formulation exhibited excellent in vitro stability in human serum and showed >97% retention in the liver up to 7 d post-administration when biodistribution studies were carried out in healthy Wistar rats. Yttrium-90 positron emission tomography scans recorded at different time points post-administration of customized dose of [90Y]YAS glass microspheres in human patients showed near-quantitative retention of the formulation in the injected lobe. Conclusions: The study confirmed the suitability of indigenously prepared [90Y]YAS glass microspheres for clinical use in the treatment of unresectable hepatocellular carcinoma.

Cancer Brachytherapy at the Nanoscale: An Emerging Paradigm

Brachytherapy is an established treatment modality that has been globally utilized for the therapy of malignant solid tumors. However, classic therapeutic sealed sources used in brachytherapy must be surgically implanted directly into the tumor site and removed after the requisite period of treatment. In order to avoid the trauma involved in the surgical procedures and prevent undesirable radioactive distribution at the cancerous site, well-dispersed radiolabeled nanomaterials are now being explored for brachytherapy applications. This emerging field has been coined "nanoscale brachytherapy". Despite present-day advancements, an ongoing challenge is obtaining an advanced, functional nanomaterial that concurrently incorporates features of high radiolabeling yield, short labeling time, good radiolabeling stability, and long tumor retention time without leakage of radioactivity to the nontargeted organs. Further, attachment of suitable targeting ligands to the nanoplatforms would widen the nanoscale brachytherapy approach to tumors expressing various phenotypes. Molecular imaging using radiolabeled nanoplatforms enables noninvasive visualization of cellular functions and biological processes in vivo. In vivo imaging also aids in visualizing the localization and retention of the radiolabeled nanoplatforms at the tumor site for the requisite time period to render safe and effective therapy. Herein, we review the advancements over the last several years in the synthesis and use of functionalized radiolabeled nanoplatforms as a noninvasive substitute to standard brachytherapy sources. The limitations of present-day brachytherapy sealed sources are analyzed, while highlighting the advantages of using radiolabeled nanoparticles (NPs) for this purpose. The recent progress in the development of different radiolabeling methods, delivery techniques and nanoparticle internalization mechanisms are discussed. The preclinical studies performed to date are summarized with an emphasis on the current challenges toward the future translation of nanoscale brachytherapy in routine clinical practices.

Exploratory analysis of 64 CuCl 2 PET-CT imaging in carcinoma prostate and its comparison with 68 Ga-PSMA-11 and 18 F-FDG PET-CT

AIM

Exploratory analysis of 64 CuCl 2 PET-CT imaging in patients of carcinoma prostate and its head-to-head comparison with 68 Ga-PSMA-11 and 18 F-FDG PET-CT.

METHODS

In this prospective study, 50 patients of biopsy-proven carcinoma prostate belonging to the entire spectrum of disease were evaluated, out of which 21 patients were for initial staging and 29 were for restaging/response evaluation. Both 64 CuCl 2 (early and delayed) and 68 Ga-PSMA-11 PET-CT were undertaken in all patients and 18 F-FDG PET-CT was done in patients whenever possible. All scans were done within a period of 2 weeks, without any interim therapeutic intervention. 64 CuCl 2 PET-CT was acquired at 1 and 3 h. We evaluated the physiological uptake of 64 CuCl 2 , correlated the uptake in primary with disease parameters like Gleason score and serum PSA levels, and compared the detection rates for primary and metastatic disease with 68 Ga-PSMA-11 and 18 F-FDG PET-CT.

RESULTS

The detection rates of primary disease were same for both 64 CuCl 2 and 68 Ga-PSMA-11 PET-CT and both agents performed similarly in detecting extra-prostatic disease. There was no statistically significant correlation observed between the uptake of 64 CuCl 2 in the primary lesion with disease parameters. With regard to the evaluation of metastatic disease, the detection rate of 64 CuCl 2 PET-CT was 86% for lymph nodes, 77.3% for skeletal metastases and 80.6% for soft tissue metastases while 68 Ga-PSMA-11 PET-CT performed better with detection rates were 98%, 99% and 85.4%, respectively. In 17 patients where 18 F-FDG PET-CT was available, 64 CuCl 2 PET-CT detected more metastatic disease than 18 F-FDG PET-CT.

CONCLUSION

64 CuCl 2 PET-CT did not show any additional advantage over 68 Ga-PSMA-11 PET-CT in evaluation of local disease or for the assessment of metastatic disease. When compared to 68 Ga-PSMA-11 PET-CT, the absence of urinary bladder and ureteric activity allows better contrast for evaluating local disease, but it does not translate into increased disease detection.

Alpha-induced production and robust radiochemical separation of 43Sc as an emerging radiometal for formulation of PET radiopharmaceuticals

Scandium-43 is an emerging PET radiometal that was produced by α-particle bombardment on natural CaCO₃ target via ^natCa (α,p) ⁴³Sc and ^natCa (α,n) ⁴³Ti→⁴³Sc reactions using K-130 cyclotron at VECC. A robust radiochemical procedure based on selective precipitation of ⁴³Sc as Sc(OH)₃ was developed for separation of the radioisotope from the irradiated target. The overall yield of the separation process was >85% and it was obtained in a form suitable for preparation of target specific radiopharmaceuticals for PET imaging of cancer.

Biochemical separation of Cetuximab-Fab from papain-digested antibody fragments and radiolabeling with 64Cu for potential use in radioimmunotheranostics

Engineered Fab fragments of monoclonal antibodies (mAbs) after radiolabeling with suitable radiometals have the potential to play a key role in personalized radioimmunotheranostics of cancer patients. In this study, we have generated Fab fragment of Cetuximab, a mAb targeting epidermal growth factor receptor (EGFR) expression and purified from the Fc and other fragments by ultrafiltration and affinity chromatography. The Cetuximab-Fab was conjugated with a suitable bifunctional chelator and radiolabeled with no-carrier-added (NCA) ⁶⁴Cu produced via ⁶⁴Zn (n, p) ⁶⁴Cu reaction in a nuclear reactor. The radioimmunoconjugate obtained after size exclusion chromatographic separation possessed >95% radiochemical purity and it retained its integrity over at least three half-lives of the radiometal. Biodistribution studies was performed in fibrosarcoma tumor bearing Swiss mice, which demonstrated the explicit need for purification of the Cetuximab-Fab from Fc fragments. Enhanced and rapid tumor uptake with decent tumor-to-background ratio with prolonged retention was observed when radiolabeled purified Cetuximab-Fab was intravenously administered in animal models. Overall, this preclinical study established the pivotal role of separation science and technology to obtain the radioimmunoconjugate with requisite purity in order to demonstrate optimal pharmacokinetics and maximized treatment efficacy.

A robust lyophilized kit for convenient one-step formulation of [68Ga]Ga-DOTA-E-[c(RGDfK)]2 in hospital radiopharmacy for clinical PET imaging

The present article describes the development of robust lyophilized kit for convenient formulation of [⁶⁸Ga]Ga-DOTA-E-[c(RGDfK)]₂ (E = glutamic acid, R = arginine, G = glycine, D = aspartic acid, f = phenylalanine, K = lysine) radiopharmaceutical for clinical use in non-invasive monitoring of malignancies overexpressing integrin α_vβ₃ receptors. Five batches of the kit were prepared with optimized kit contents, all of which showed high ⁶⁸Ga-radiolabeling yield (>98%). Pre-clinical evaluation of the [⁶⁸Ga]Ga-radiotracer in SCID mice bearing FTC133 tumour exhibited significant accumulation in the tumor xenograft. Preliminary human clinical investigation carried out in a 60 year old male patient with metastatic lung cancer revealed high radiotracer uptake in the tumor along with satisfactory target to non-target contrast. The developed kit formulation also showed a long shelf-life of at least 12 months on storage at 0 °C. All these results point towards the promising attributes of the developed kit formulation for convenient preparation of [⁶⁸Ga]Ga-DOTA-E-[c(RGDfK)]₂ for routine clinical use.

A review of advances in the last decade on targeted cancer therapy using 177Lu: focusing on 177Lu produced by the direct neutron activation route

Lutetium-177 [T½ = 6.76 d; Eβ (max) = 0.497 MeV; maximum tissue range ~2.5 mm; 208 keV γ-ray] is one of the most important theranostic radioisotope used for the management of various oncological and non-oncological disorders. The present review chronicles the advancement in the last decade in 177Lu-radiopharmacy with a focus on 177Lu produced via direct 176Lu (n, γ) 177Lu nuclear reaction in medium flux research reactors. The specific nuances of 177Lu production by various routes are described and their pros and cons are discussed. Lutetium, is the last element in the lanthanide series. Its chemistry plays a vital role in the preparation of a wide variety of radiopharmaceuticals which demonstrate appreciable in vivo stability. Traditional bifunctional chelators (BFCs) that are used for 177Lu-labeling are discussed and the upcoming ones are highlighted. Research efforts that resulted in the growth of various 177Lu-based radiopharmaceuticals in preclinical and clinical settings are provided. This review also summarizes the results of clinical studies with potent 177Lu-based radiopharmaceuticals that have been prepared using medium specific activity 177Lu produced by direct neutron activation route in research reactors. Overall, the review amply demonstrates the practicality of the medium specific activity 177Lu towards formulation of various clinically useful radiopharmaceuticals, especially for the benefit of millions of cancer patients in developing countries with limited reactor facilities.

Facile Synthesis of a Pt(IV) Prodrug of Cisplatin and Its Intrinsically 195mPt Labeled Analog: A Step Closer to Cancer Theranostic

Background, Aims and Objectives:

Cisplatin is extensively used in chemotherapy for treatment of a broad range of cancers. But its undesired side reactions with biomolecules that lead to severe side effects especially on kidney and nervous system, are limiting its clinical utility. To reduce its side effects, the kinetically inert Pt(IV) prodrug was recognized as an alternative approach from satisfactory results of preliminary experiments. But, its approval as anticancer drug for clinical use requires detailed investigations of its anticancer action and pharmacological pathways by employing its analogue which can be traced by a suitable technique. As a step closer towards translation of Pt(IV)-based prodrug from research to clinical level, a protocol for efficient synthesis of ^195mPt-radiolabeled Pt(IV) prodrug was devised.

Materials and Methods:

In order to achieve the aim, we started synthesis from elemental platinum avoiding lengthy steps. The synthesis protocol was standardized on its cold analogue, as [PtCl₂(NH₃)₂(OCOCH₂CH₂COOH)₂] which has been characterized with nuclear magnetic resonance (¹H, ¹³C{1H} and ¹⁹⁵Pt{1H}) spectroscopy, microanalyses and cyclic voltammetry. Also, cytotoxicity of [PtCl₂(OCOCH₂CH₂COOH)₂(NH₃)₂] was evaluated against MCF-7 human breast cancer cell lines using cisplatin as test control.

Results:

Intrinsically, ^195mPt-labeled analogue of prodrug was obtained with high radionuclidic and radiochemical purity. It was confirmed by chromatography and γ-ray spectrometry.

Conclusion:

The ^195mPt-radiolabeled prodrug was synthesized in a facile manner. It can be utilized in evaluating the mechanism of anticancer action and pharmacokinetics by enabling synergistic use of molecular imaging and targeted drug delivery.

Mechanochemically synthesized mesoporous alumina: a smart new-generation sorbent for preparation of chromatographic 188W/188Re generator

Abstract

In an effort towards affordable availability of chromatographic 188W/188Re generators for widespread clinical use, we report the mechanochemical synthesis of mesoporous alumina as an advanced sorbent material for preparation of the generator. The synthesized material exhibits remarkably high sorption capacity (550 ± 12 mg W/g), which is adequate for preparation of clinical-scale generators using low specific activity (LSA) 188W produced in medium flux research reactors. Sorption of 188W in mesoporous alumina follows Freundlich adsorption isotherm and pseudo second order kinetics, indicating that the process is chemisorption. A clinical-scale (~ 14.0 GBq) 188W/188Re generator was developed and its performance was evaluated over a period of 6 months. Rhenium-188 could be consistently obtained from the generator with high yield (> 80%) and it met all the requirements for clinical use. The present strategy is expected to increase the scope of separation chemistry for availing clinical-grade 188Re for the benefit of millions of cancer patients world over.

Graphic abstract

IAEA contribution to the development of 64Cu radiopharmaceuticals for theranostic applications

Copper-64 is a very attractive radioisotope with unique nuclear properties that allow using it as both a diagnostic and therapeutic agent, thus providing an almost ideal example of a theranostic radionuclide. A characteristic of Cu-64 stems from the intrinsic biological nature of copper ions that play a fundamental role in a large number of cellular processes. Cu-64 is a radionuclide that reflects the natural biochemical pathways of Cu-64 ions, therefore, can be exploited for the detection and therapy of certain malignancies and metabolic diseases. Beside these applications of Cu-64 ions, this radionuclide can be also used for radiolabelling bifunctional chelators carrying a variety of pharmacophores for targeting different biological substrates. These include peptide-based substrates and immunoconjugates as well as small-molecule bioactive moieties. Fueled by the growing interest of Member States (MS) belonging to the International Atomic Energy Agency (IAEA) community, a dedicated Coordinated Research Project (CRP) was initiated in 2016, which recruited thirteen participating MS from four continents. Research activities and collaborations between the participating countries allowed for collection of an impressive series of results, particularly on the production, preclinical evaluation and, in a few cases, clinical evaluation of various ⁶⁴Cu-radiopharmaceuticals that may have potential impact on future development of the field. Since this CRP was finalized at the beginning of 2020, this short review summarizes outcomes, outputs and results of this project with the purpose to propagate to other MS and to the whole scientific community, some of the most recent achievements on this novel class of theranostic ⁶⁴Cu-pharmaceuticals.

Formulation of ‘ready-to-use’ human clinical doses of 177Lu-labeled bisphosphonate amide of DOTA using moderate specific activity 177Lu and its preliminary evaluation in human patient

Radiolabeled macrocyclic bisphosphonate ligands have recently been demonstrated to be highly efficacious in treatment of patients with painful bone metastases. Herein, we report a robust protocol for formulation of therapeutically relevant doses of 177Lu-labeled bisphosphonate amide of DOTA (BPAMD) using moderate specific activity 177Lu produced by direct (n,γ) route and its preliminary investigation in human patients. Doses (2.8 ± 0.2 GBq) were formulated with high radiochemical purity (98.3 ± 0.4 %) using a protocol optimized after extensive radiochemical studies. In vitro binding studies with mineralized osteosarcoma cells demonstrated specific binding of the radiotracer. Biodistribution studies in healthy Wistar rats demonstrated rapid skeletal accumulation with fast clearance from the non-target organs. In a patient administered with 555 MBq dose of 177Lu-BPAMD, intense radiotracer uptake was observed in the metastatic skeletal lesions with insignificant uptake in any other major non-targeted organs. Preliminary clinical investigations carried out after administration of 2.6 GBq of 177Lu-BPAMD revealed significant reduction in pain after 1 week without any adverse effects. The developed protocol for formulation of 177Lu-BPAMD doses using moderate specific activity carrier added 177Lu has been found to be effective and warrants wider investigations in patients with painful skeletal metastases.

A simple and robust method for radiochemical separation of no-carrier-added 64Cu produced in a research reactor for radiopharmaceutical preparation

Copper-64 is an excellent theranostic radiometal that is gaining renewed attention of the clinical community in the recent times. In order to meet the increasing demand of this radiometal, we have demonstrated the viability of its production via ⁶⁴Zn (n,p) ⁶⁴Cu reaction in a nuclear reactor. A semi-automated radiochemical separation module based on selective extraction of ⁶⁴Cu as dithizonate complex was developed. The maximum available activity at the end of irradiation was ~ 700 MBq. The overall yield of ⁶⁴Cu after the separation process was >85% and it could be obtained with ~12 GBq/μg specific activity, >99.9% radionuclidic purity and >98% radiochemical purity. The separated ⁶⁴Cu could be utilized for preparation of a wide variety of radiopharmaceuticals.

A kit based methodology for convenient formulation of 166Ho-Chitosan complex for treatment of liver cancer

The effectiveness of ¹⁶⁶Ho-chitosan complex as a radiopharmaceutical for trans-arterial radiation therapy of liver cancer has been established in clinical trials. We have developed a simple kit-bade strategy for convenient formulation of therapeutically relevant doses of ¹⁶⁶Ho-chitosan complex in a hospital radiopharmacy in order to facilitate its widespread utilization. Quality control studies established the suitability of the radiopharmaceutical formulated using the developed strategy for in vivo administration. Biodistribution studies in normal Wistar rats showed excellent retention of the radiopharmaceutical in the liver, thus, paving the way towards utility of this approach in clinical context.

Mechanochemically synthesized mesoporous alumina: An advanced sorbent for post-processing concentration of 131I for cancer therapy

High radioactive concentration of ¹³¹I in the form of ¹³¹I[NaI] solution is essential for preparation of large-dose therapeutic capsules used in the management of thyroid cancer. In this communication, we report the synthesis of mesoporous alumina sorbent (surface area = 292 ± 28 m²/g, mean pore diameter = 6.8 ± 0.7 nm) by a novel solid state mechanochemical approach and its utilization in post-processing concentration of ¹³¹I. The overall yield of ¹³¹I after the concentration procedure was >90% and ¹³¹I[NaI] solution could be obtained with appreciably high (1.7 TBq/mL) radioactive concentration, suitable for use in nuclear medicine. The promising results obtained in this study would stimulate greater utilization of this new class of sorbents in sample preparations by solid phase extraction procedures for societal benefits.

A facile method for electrochemical separation of 181-186Re from proton irradiated natural tungsten oxide target

Routine availability of high specific activity ¹⁸⁶Re would provide a significant boost to the development of potent theranostic radiopharmaceuticals. In the present study, ^181-186Re was produced by proton bombardment (12 MeV, average beam intensity 180 nΑ) for 60 h on natural tungsten oxide target. A facile electrochemical method has been developed for radiochemical separation of Re radioisotopes from irradiated target material. The overall yield of the process was >80% and Re radioisotopes could be separated in a form suitable for preparation of radiopharmaceuticals.

An improved kit formulation for one-pot synthesis of [99m Tc]Tc-HYNIC-E[c(RGDfK)]2 for routine clinical use in cancer imaging

Radiolabeled Arg-Gly-Asp (RGD) peptide derivatives have immense potential for non-invasive monitoring of malignancies overexpressing integrin α_v β₃ receptors. Easy availability of suitable radiotracers would augment the utility of this class of molecular imaging agents. Towards this, the present article describes the development of an improved lyophilized kit for the routine clinical formulation of [^99m Tc]Tc complex of HYNIC-conjugated dimeric cyclic RGD peptide derivative E-[c(RGDfK)]₂ (E = glutamic acid, f = phenyl alanine, K = lysine) without using Sn²⁺ and systematic evaluation of its efficacy. Five batches of the kits were prepared, and [^99m Tc]Tc-HYNIC-E[c(RGDfK)]₂ radiotracer was synthesized with high radiochemical purity (98.6 ± 0.5%) and specific activity (124.8 GBq/μmol) using the kits. Biodistribution studies in C57BL/6 mice bearing melanoma tumor exhibited significant accumulation of the radiotracer in tumor (5.32 ± 0.56 %ID/g at 60 min p.i.), and this uptake was also found to be receptor-specific by blocking studies. Preliminary human clinical investigations carried out in 10 breast cancer patients revealed high radiotracer uptake in the tumor along with good tumor-to-background contrast. The developed kit formulation showed an exceptionally high shelf-life of at least 18 months. These results demonstrated promising attributes of the developed kit formulation and warrant more extensive clinical investigations.

Clinical scale synthesis of intrinsically radiolabeled and cyclic RGD peptide functionalized 198Au nanoparticles for targeted cancer therapy

INTRODUCTION

The emerging concept of intrinsically radiolabeled nanoparticles has the potential to transform the preclinical and clinical studies by improving the in vivo stability and demonstrating minimal alteration in the inherent pharmacokinetics of the nanoparticles. In this paper, a simple and efficient single-step method for clinical scale synthesis of intrinsically radiolabeled ¹⁹⁸Au nanoparticles conjugated with cyclic arginine-glycine-aspartate peptide (¹⁹⁸AuNP-RGD) is reported for potential use in targeted cancer therapy.

METHODS

Large radioactive doses (>37 GBq) of ¹⁹⁸AuNP-RGD were synthesized by reaction of ¹⁹⁸Au-HAuCl₄ with cyclic RGD peptide. The synthesized nanoparticles were characterized by various analytical techniques. In vitro cell binding studies were carried out in B16F10 (murine melanoma) cell line. Biodistribution studies were carried out in melanoma tumor bearing C57BL/6 mice to demonstrate the tumor targeting ability of ¹⁹⁸AuNP-RGD. The therapeutic efficacy of ¹⁹⁸AuNP-RGD was evaluated by carrying out systematic tumor regression studies in melanoma tumor bearing mice after intravenous administration of the radioactive doses.

RESULTS

Well dispersed and biocompatible nanoparticles (~12.5 nm diameter) could be synthesized with excellent radiochemical and colloidal stability. In vitro studies exhibited the cell binding affinity and specificity of ¹⁹⁸AuNP-RGD towards melanoma cell line. A high uptake of 8.7 ± 2.1%ID/g in the tumor was observed within 4 h post-injection (p.i.). Significant decrease in tumor uptake of ¹⁹⁸AuNP-RGD (2.9 ± 0.8%ID/g) at 4 h p.i. on co-injection of a blocking dose of the peptide suggested that tumor localization of the intrinsically radiolabeled nanoparticles was receptor mediated. Administration of 37.0 MBq of ¹⁹⁸AuNP-RGD resulted in significant regression of tumor growth with no apparent body weight loss over a period of 15 d.

CONCLUSIONS

Overall, these promising results demonstrate the suitability of ¹⁹⁸AuNP-RGD as an advanced functional nanoplatform for targeted cancer therapy.

Facile radiochemical separation of clinical-grade 90Y from 90Sr by selective precipitation for targeted radionuclide therapy

INTRODUCTION

The widespread clinical utilization of ⁹⁰Y for preparation of target specific radiopharmaceuticals demands development of a facile, efficient and cost-effective method for radiochemical separation of ⁹⁰Y from ⁹⁰Sr via⁹⁰Sr/⁹⁰Y generator. In this article, we describe an efficient and facile method for radiochemical separation of ⁹⁰Y from ⁹⁰Sr for preparation of radiopharmaceuticals by exploiting the large difference in the solubility product constants (K_sp) of Y(OH)₃ and Sr(OH)₂.

METHODS

A two-step radiochemical separation procedure based on selective precipitation of ⁹⁰Y under alkaline conditions from ⁹⁰Sr/⁹⁰Y equilibrium mixture was developed. The ⁹⁰Y(OH)₃ colloid formed at pH ~ 10 was selectively trapped in 0.22 μm sterile filter and was subsequently retrieved by dissolution in HCl solution. Detailed quality control analyses of obtained ⁹⁰Y were carried out and its utility towards preparation of different radiopharmaceuticals was assessed.

RESULTS

Using the same feed solution of ⁹⁰Sr (3.7 GBq), consistent and repeated separation of ⁹⁰Y could be achieved in different batches with >85% yield and >99.999% radionuclidic purity. Yttrium-90 obtained from this process was found suitable for preparation of therapeutically relevant doses of three different radiopharmaceutical formulations, namely, ⁹⁰Y-DOTA-TATE, ⁹⁰Y-PSMA-617 and ⁹⁰Y-CHX-A″-DTPA-Cetuximab with >95% radiochemical purity.

CONCLUSIONS

The promising results obtained in this study would facilitate implementation of the developed technique for obtaining ⁹⁰Y in adequate quantity and of required purity from a centralized radiopharmacy setup.

Radionuclide generators: the prospect of availing PET radiotracers to meet current clinical needs and future research demands

Targeted molecular imaging with positron emission tomography (PET) constitutes a successful technique for detecting and diagnosing disease conditions promptly and accurately, and for effectively prognosticating outcomes and treating patients with a tailored and more individualized intervention. In order to expand the success of PET in nuclear medicine, it is important to assure access to radiotracers of desired quantities and qualities. In this context, the benefit of accessing PET radiotracers through a radionuclide generator (RNG) cannot be overstated, as generators offer the potential of enriching the PET radiotracer arsenal at the medical centers both with and without onsite cyclotrons. While RNG technology to avail PET tracers is in its infancy, their use is expected to revitalize current PET practices and seems poised to broaden the palette of PET in nuclear medicine in the foreseeable future. In this review, we discuss the principles of RNGs, assess major parent/daughter pairs of interest for PET, RNGs currently in use in clinical PET, and identify the potentially useful RNGs which have made substantial progress or are likely to be used in daily clinical practices in the near future. Availability of the parent radionuclides required for PET RNGs is an important criterion and hence their production will also be reviewed. This overview outlines a critical assessment of RNGs to avail PET tracers, the contemporary status of RNGs, and key challenges and apertures to the near future.

Targeted α-therapy of prostate cancer using radiolabeled PSMA inhibitors: a game changer in nuclear medicine

Prostate cancer (PCa) is one of the most common malignancies in men and is a major contributor to cancer related deaths worldwide. Metastatic spread and disease progression under androgen deprivation therapy signify the onset of metastatic castration resistant prostate cancer (mCRPCa)-the lethal form of the disease, which severely deteriorates the quality of life of patients. Over the last decade, tremendous progress has been made toward identifying appropriate molecular targets that could enable efficient in vivo targeting for non-invasive imaging and therapy of mCPRCa. In this context, a promising enzymatic target is prostate specific membrane antigen (PSMA), which is overexpressed on PCa cells, in proportion to the stage and grade of the tumor progression. This is especially relevant for mCRPCa, which has significant overexpression of PSMA. For therapy of mCRPCa, several nuclear medicine clinics all over the world have confirmed that 177Lu-labeled-PSMA enzyme inhibitors (177Lu-PSMA-617 and 177Lu-PSMA I&T) have a favorable dosimetry and convincing therapeutic response. However, ~30% of patients were found to be short or non-responders and dose escalation was severely limited by chronic hematological toxicity. Such limitations could be better overcome by targeted alpha therapy (TAT) which has the potential to bring a paradigm shift in treatment of mCRPCa patients. This concise review presents an overview of the successes and challenges currently faced in TAT of mCRPCa using radiolabeled PSMA inhibitors. The preclinical and clinical data reported to date are quite promising, and it is expected that this therapeutic modality will play a pivotal role in advanced stage PCa management in the foreseeable future.

Barium titanate microparticles as potential carrier platform for lanthanide radionuclides for their use in the treatment of arthritis

Since the inception of radiation synovectomy, a host of radioactive colloids and microparticles incorporating suitable therapeutic radionuclides have been proposed for the treatment of arthritis. The present article reports the synthesis and evaluation of barium titanate microparticles as an innovative and effective carrier platform for lanthanide radionuclides in the preparation of therapeutic agents for treatment of arthritis. The material was synthesized by mechanochemical route and characterized by X-ray diffraction, scanning electron microscopy, surface area, and particle size distribution analyses. Loading of lanthanide radionuclides (¹⁶⁶ Ho, ¹⁵³ Sm, ¹⁷⁷ Lu, and ¹⁶⁹ Er) on the microparticles was achieved in high yield (> 95%) resulting in the formulation of loaded particulates with excellent radiochemical purities (> 99%). Radiolanthanide-loaded microparticles exhibited excellent in vitro stability in human serum. In vitro diethylene triamine pentaacetic acid challenge study indicated fairly strong chemical association of lanthanides with barium titanate microparticles. Long-term biodistribution studies carried out after administration of ¹⁷⁷ Lu-loaded microparticles into one of the knee joints of normal Wistar rats revealed near-complete retention of the formulation (> 96% of the administered radioactivity) within the joint cavity even 14 days post-administration. The excellent localization of the loaded microparticles was further confirmed by sequential whole-body radio-luminescence imaging studies carried out using ¹⁶⁶ Ho-loaded microparticles.

A "mix-and-use" approach for formulation of human clinical doses of 177 Lu-DOTMP at hospital radiopharmacy for management of pain arising from skeletal metastases

Use of bone-seeking radiopharmaceuticals is an established modality in the palliative care of pain due to skeletal metastases. ¹⁷⁷ Lu-DOTMP is a promising radiopharmaceutical for this application owing to the ideally suited decay properties of ¹⁷⁷ Lu and excellent thermodynamic stability and kinetic rigidity of the macrocyclic complex. The aim of the present study is to develop a robust and easily adaptable protocol for formulation of clinical doses of ¹⁷⁷ Lu-DOTMP at hospital radiopharmacy. After extensive radiochemical studies, an optimized strategy for formulation of clinical doses of ¹⁷⁷ Lu-DOTMP was developed, which involves simple mixing of approximately 3.7 GBq of ¹⁷⁷ Lu activity as ¹⁷⁷ LuCl₃ solution to an aqueous solution containing 5 mg of DOTMP and 8 mg of NaHCO₃ . The proposed protocol yielded ¹⁷⁷ Lu-DOTMP with >98% radiochemical purity, and the resultant formulation showed excellent in vitro stability and desired pharmacokinetic properties in animal model. Preliminary clinical investigations in 5 patients showed specific skeletal accumulation with preferential localization in the osteoblastic lesion sites and almost no uptake in soft tissue or any other major nontarget organ. The developed "mix-and-use" strategy would be useful for large number of nuclear medicine centers having access to ¹⁷⁷ Lu activity and would thereby accelerate the clinical translation of ¹⁷⁷ Lu-DOTMP.

Radiolabeled inorganic nanoparticles for positron emission tomography imaging of cancer: an overview

Over the last few years, a plethora of radiolabeled inorganic nanoparticles have been developed and evaluated for their potential use as probes in positron emission tomography (PET) imaging of a wide variety of cancers. Inorganic nanoparticles represent an emerging paradigm in molecular imaging probe design, allowing the incorporation of various imaging modalities, targeting ligands, and therapeutic payloads into a single vector. A major challenge in this endeavor is to develop disease-specific nanoparticles with facile and robust radiolabeling strategies. Also, the radiolabeled nanoparticles should demonstrate adequate in vitro and in vivo stability, enhanced sensitivity for detection of disease at an early stage, optimized in vivo pharmacokinetics for reduced non-specific organ uptake, and improved targeting for achieving high efficacy. Owing to these challenges and other technological and regulatory issues, only a single radiolabeled nanoparticle formulation, namely "C-dots" (Cornell dots), has found its way into clinical trials thus far. This review describes the available options for radiolabeling of nanoparticles and summarizes the recent developments in PET imaging of cancer in preclinical and clinical settings using radiolabeled nanoparticles as probes. The key considerations toward clinical translation of these novel PET imaging probes are discussed, which will be beneficial for advancement of the field.

Initial Clinical Experience with 68Ga-DOTA-NOC Prepared Using 68Ga from Nanoceria-polyacrylonitrile Composite Sorbent-based 68Ge/68Ga Generator and Freeze-dried DOTA-NOC Kits

Somatostatin receptor positron emission tomography–computed tomography (PET/CT) with ⁶⁸Ga-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) peptides have become an indispensable part of disease assessment in patients with neuroendocrine tumors and forms the basis of personalized therapy with peptide receptor-based radionuclide therapy. With growing utilization of PET/CT in developing countries, availability of the indigenous GMP-certified ⁶⁸Ge/⁶⁸Ga generators is expected to further promote cost-effective molecular imaging service to the cancer patients. We present our initial clinical experience in 32 patients injected with ⁶⁸Ga-DOTA-NOC prepared using ⁶⁸Ga eluted from Bhabha Atomic Research Centre nanoceria-polyacrylonitrile sorbent-based ⁶⁸Ge/⁶⁸Ga generator and freeze-dried DOTA-NOC cold kits.

Formulation and purification of therapeutic dose of 90Y-labeled peptides: Some interesting radiochemistry aspects

Yttrium-90 obtained from most of the ⁹⁰Sr/⁹⁰Y generators contains ⁹⁰Sr impurity above permissible limit for human administration. A protocol has been optimized for formulation of therapeutic dose of ⁹⁰Y-DOTA-Tyr³-octreotate (⁹⁰Y-DOTA-TATE) and removal of ⁹⁰Sr impurity from it. The radiochemical purity of ⁹⁰Y-DOTA-TATE was found to be >98% and it met the requirements for clinical use. The radiopharmaceutical was used in preliminary clinical investigation in patients with neuroendocrine tumors. This promising strategy would aid toward widespread clinical utilization of ⁹⁰Sr/⁹⁰Y generators.

New Delhi metallo-β-lactamase and extended spectrum β-lactamases co-producing isolates are high in community-acquired urinary infections in Assam as detected by a novel multiplex polymerase chain reaction assay

BACKGROUND

The ability of microorganisms to evade antibiotic pressure is challenging in healthcare as patients have little or no drug treatment options. Detection of the prevalence of antibacterial resistance pattern helps towards improved antibiotic policy and empirical treatment.

OBJECTIVES

We carried out antibiogram profiling and documented the prevalence and co-prevalence of New Delhi metallo-β-lactamase (NDM) and extended spectrum β-lactamases (ESBL) encoding genes in urinary Escherichia coli and Klebsiella pneumonia isolates.

MATERIALS AND METHODS

Antibiotic susceptibilities were tested for 241 isolates of E. coli and K. pneumoniae from urine samples collected from out- and hospitalised patients. Polymerase chain reaction (PCR) was carried out on isolates tested positive for phenotypic production of metallo-β-lactamase and ESBL. A multiplex PCR assay was designed to detect the genes.

RESULTS

Multiplex PCR assay designed had a limit of detection of 10 3 CFU/mL in vitro. NDM detected was significantly higher among K. pneumoniae compared to E. coli (69.2% vs. 18.2%; P = 0.001). Of 17, 14 NDM positive isolates also harboured ESBL genes. The co-production of CTX-M + TEM + NDM (3/9; 33.3% and 5/8; 62.5%) was most common in K. pneumoniae and E. coli, respectively while CTX-M + TEM + SHV + NDM was found in one isolate. Of the 156 phenotypically ESBL producing isolates, CTX-M, TEM and SHV was detected by PCR in 85, 53 and 24 isolates, respectively.

CONCLUSION

NDM and ESBL co-producing isolates were both community (64.7%) and hospital (35.29%) acquired among E. coli. Antibiotic resistance can be effectively evaluated by a cost and time effective molecular method, such as the multiplex PCR used in this study, which complement culture and sensitivity tests.

Mechanochemical synthesis of mesoporous tin oxide: a new generation nanosorbent for (68)Ge/(68)Ga generator technology

The present article reports the synthesis and characterization of mesoporous tin oxide (MTO) nanoparticles by a solid-state mechanochemical route. The synthesized material was used as an advanced sorbent material for (68)Ge/(68)Ga radionuclide generator technology. Gallium-68 (t½ = 68 min) obtained from the (68)Ge/(68)Ga generator is an important diagnostic radioisotope which holds tremendous potential in the non-invasive monitoring of various diseases, including cancer, using positron emission tomography (PET). The crystallite size of the MTO nanoparticles was in the range of 6-12 nm with a large surface area of 265 ± 16 m(2) g(-1), while the mean pore radius was found to be 2.1 ± 0.6 nm. Determination of the zeta-potential of the MTO nanoparticles dispersed in solutions at different pH values aided in understanding the sorption and separation mechanisms, which were based on the surface charge developed on the nanosorbent. The sorption capacity observed under column-flow conditions was 85 ± 5 mg Ge per g of nanosorbent. A clinical-scale (68)Ge/(68)Ga generator (740 MBq) was developed using this nanosorbent. Gallium-68 could be regularly eluted from this generator over a prolonged period of 1 year with >70% elution yield and met all the requirements for clinical use. The suitability of (68)Ga obtained from it was evaluated in preclinical settings by the preparation of a (68)Ga-labeled peptide containing the arginine-glycine-aspartic acid (RGD) motif. To the best of our knowledge, this is the first report on the synthesis of MTO nanoparticles by a mechanochemical route which could be effectively utilized for the routine preparation of clinical-scale (68)Ge/(68)Ga generators. The promising results obtained in this study would facilitate greater implementation of mechanochemistry for the synthesis of nanosorbents for radionuclide generator technology since this method is simple, economical and convenient.

Molecular Imaging of Breast Cancer: Role of RGD Peptides

Breast cancer is the leading cause of cancer deaths among women of all ages worldwide. With advances in molecular imaging procedures, it has been possible to detect breast cancer in its early stage, determine the extent of the disease to administer appropriate therapeutic protocol and also monitor the effects of treatment. By accurately characterizing the tumor properties and biological processes involved, molecular imaging can play a crucial role in minimizing the morbidity and mortality associated with breast cancer. The integrin αvβ3 plays an important role in breast cancer angiogenesis and is expressed on tumor endothelial cells as well as on some tumor cells. It is a receptor for the extracellular matrix proteins with the exposed arginine-glycine-aspartic acid (RGD) tripeptide sequence and therefore RGD peptides can preferentially bind to integrin αvβ3. In this context, targeting tumor vasculature or tumor cells by RGD-based probes is a promising strategy for molecular imaging of breast cancer. Using RGD-based probes, several preclinical studies have employed different imaging modalities such as positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), ultrasound and optical imaging for visualization of integrin αvβ3 expression in breast cancer models. Limited clinical trials using (18)F-labeled RGD peptides have also been initiated for non-invasive detection and staging of breast cancer. Herein, we provide a comprehensive overview of the latest advances in molecular imaging of breast cancer using RGD peptide-based probes and discuss the challenges and opportunities for advancement of the field. The reported strategies for molecular imaging of breast cancer using RGD peptide-based probes holds promise for making clinically translatable advances that can positively impact the overall diagnostic and therapeutic processes and result in improved quality of life for breast cancer patients.