Targeted alpha therapy (TAT) offers advantages over current β-emitting conjugates for peptide receptor radionuclide therapy (PRRT) of neuroendocrine tumors. PRRT with
Lu-DOTATATE or
Y-DOTATOC has ...shown dose-limiting nephrotoxicity due to radiopeptide retention in the proximal tubules. Pharmacological protection can reduce renal uptake of radiopeptides, e.g., positively charged amino acids, to saturate in the proximal tubules, thereby enabling higher radioactivity to be safely administered. The aim of this preclinical study was to evaluate the therapeutic effect of
Bi-DOTATATE with and without renal protection using L-lysine in mice. Tumor uptake and kinetics as a function of injected mass of peptide (range 0.03-3 nmol) were investigated using
In-DOTATATE. These results allowed estimation of the mean radiation absorbed tumor dose for
Bi-DOTATATE. Pharmacokinetics and dosimetry of
Bi-DOTATATE was determined in mice, in combination with renal protection. A dose escalation study with
Bi-DOTATATE was performed to determine the maximum tolerated dose (MTD) with and without pre-administration of L-lysine as for renal protection. Neutrophil gelatinase-associated lipocalin (NGAL) served as renal biomarker to determine kidney injury.
The maximum mean radiation absorbed tumor dose occurred at 0.03 nmol and the minimum at 3 nmol. Similar mean radiation absorbed tumor doses were determined for 0.1 and 0.3 nmol with a mean radiation absorbed dose of approximately 0.5 Gy/MBq
Bi-DOTATATE. The optimal mass of injected peptide was found to be 0.3 nmol. Tumor uptake was similar for
In-DOTATATE and
Bi-DOTATATE at 0.3 nmol peptide. Lysine reduced the renal uptake of
Bi-DOTATATE by 50% with no effect on the tumor uptake. The MTD was <13.0 ± 1.6 MBq in absence of L-lysine and 21.7 ± 1.9 MBq with L-lysine renal protection, both imparting an LD
mean renal radiation absorbed dose of 20 Gy. A correlation was found between the amount of injected radioactivity and NGAL levels.
The therapeutic potential of
Bi-DOTATATE was illustrated by significantly decreased tumor burden and improved overall survival. Renal protection with L-lysine immediately prior to TAT with
Bi-DOTATATE prolonged survival providing substantial evidence for pharmacological nephron blockade to mitigate nephrotoxicity.
A blind performance test was conducted to evaluate dose-calibrator measurements at nuclear pharmacies in the United States (US). Two test-sample geometries were chosen to represent those used for ...measurements of
90Y-ibritumomab tiuxetan (ZEVALIN
®). The radioactivity concentration of test-samples was verified by the US National Institute of Standards and Technology. Forty-five results were reported by 10 participants. Eighty percent of reported values were within the US Pharmacopoeia content standard (±10%) for
90Y-ZEVALIN
®. All results were within US Nuclear Regulatory Commission conformance limits (±20%) for defining therapeutic misadministrations.
Bismuth (
Bi, T
= 45.6 min) is one of the most frequently used α-emitters in cancer research. High specific activity radioligands are required for peptide receptor radionuclide therapy. The use of ...generators containing less than 222 MBq
Ac (actinium), due to limited availability and the high cost to produce large-scale
Ac/
Bi generators, might complicate in vitro and in vivo applications though.Here we present optimized labelling conditions of a DOTA-peptide with an
Ac/
Bi generator (< 222 MBq) for preclinical applications using DOTA-Tyr
-octreotate (DOTATATE), a somatostatin analogue. The following labelling conditions of DOTATATE with
Bi were investigated; peptide mass was varied from 1.7 to 7.0 nmol, concentration of TRIS buffer from 0.15 mol.L
to 0.34 mol.L
, and ascorbic acid from 0 to 71 mmol.L
in 800 μL. All reactions were performed at 95 °C for 5 min. After incubation, DTPA (50 nmol) was added to stop the labelling reaction. Besides optimizing the labelling conditions, incorporation yield was determined by ITLC-SG and radiochemical purity (RCP) was monitored by RP-HPLC up to 120 min after labelling. Dosimetry studies in the reaction vial were performed using Monte Carlo and in vitro clonogenic assay was performed with a rat pancreatic tumour cell line, CA20948.
At least 3.5 nmol DOTATATE was required to obtain incorporation ≥ 99 % with 100 MBq
Bi (at optimized pH conditions, pH 8.3 with 0.15 mol.L
TRIS) in a reaction volume of 800 μL. The cumulative absorbed dose in the reaction vial was 230 Gy/100 MBq in 30 min. A minimal final concentration of 0.9 mmol.L
ascorbic acid was required for ~100 MBq (t = 0) to minimize radiation damage of DOTATATE. The osmolarity was decreased to 0.45 Osmol/L.Under optimized labelling conditions,
Bi-DOTATATE remained stable up to 2 h after labelling, RCP was ≥ 85 %. In vitro showed a negative correlation between ascorbic acid concentration and cell survival.
Bismuth-DOTA-peptide labelling conditions including peptide amount, quencher and pH were optimized to meet the requirements needed for preclinical applications in peptide receptor radionuclide therapy.
Targeted alpha therapy (TAT) offers advantages over current beta -emitting conjugates for peptide receptor radionuclide therapy (PRRT) of neuroendocrine tumors. PRRT with super(177)Lu-DOTATATE or ...super(90)Y-DOTATOC has shown dose-limiting nephrotoxicity due to radiopeptide retention in the proximal tubules. Pharmacological protection can reduce renal uptake of radiopeptides, e.g., positively charged amino acids, to saturate in the proximal tubules, thereby enabling higher radioactivity to be safely administered. The aim of this preclinical study was to evaluate the therapeutic effect of super(213)Bi-DOTATATE with and without renal protection using L-lysine in mice. Tumor uptake and kinetics as a function of injected mass of peptide (range 0.03-3 nmol) were investigated using super(111)In-DOTATATE. These results allowed estimation of the mean radiation absorbed tumor dose for super(213)Bi-DOTATATE. Pharmacokinetics and dosimetry of super(213)Bi-DOTATATE was determined in mice, in combination with renal protection. A dose escalation study with super(213)Bi-DOTATATE was performed to determine the maximum tolerated dose (MTD) with and without pre-administration of l-lysine as for renal protection. Neutrophil gelatinase-associated lipocalin (NGAL) served as renal biomarker to determine kidney injury. The maximum mean radiation absorbed tumor dose occurred at 0.03 nmol and the minimum at 3 nmol. Similar mean radiation absorbed tumor doses were determined for 0.1 and 0.3 nmol with a mean radiation absorbed dose of approximately 0.5 Gy/MBq super(213)Bi-DOTATATE. The optimal mass of injected peptide was found to be 0.3 nmol. Tumor uptake was similar for super(111)In-DOTATATE and super(213)Bi-DOTATATE at 0.3 nmol peptide. Lysine reduced the renal uptake of super(213)Bi-DOTATATE by 50% with no effect on the tumor uptake. The MTD was <13.0 plus or minus 1.6 MBq in absence of l-lysine and 21.7 plus or minus 1.9 MBq with l-lysine renal protection, both imparting an LD sub(50) mean renal radiation absorbed dose of 20 Gy. A correlation was found between the amount of injected radioactivity and NGAL levels. The therapeutic potential of super(213)Bi-DOTATATE was illustrated by significantly decreased tumor burden and improved overall survival. Renal protection with l-lysine immediately prior to TAT with super(213)Bi-DOTATATE prolonged survival providing substantial evidence for pharmacological nephron blockade to mitigate nephrotoxicity.
Background Targeted alpha therapy (TAT) offers advantages over current beta-emitting conjugates for peptide receptor radionuclide therapy (PRRT) of neuroendocrine tumors. PRRT with 177Lu-DOTATATE or ...90Y-DOTATOC has shown dose-limiting nephrotoxicity due to radiopeptide retention in the proximal tubules. Pharmacological protection can reduce renal uptake of radiopeptides, e.g., positively charged amino acids, to saturate in the proximal tubules, thereby enabling higher radioactivity to be safely administered. The aim of this preclinical study was to evaluate the therapeutic effect of 213Bi-DOTATATE with and without renal protection using L-lysine in mice. Tumor uptake and kinetics as a function of injected mass of peptide (range 0.03-3 nmol) were investigated using 111In-DOTATATE. These results allowed estimation of the mean radiation absorbed tumor dose for 213Bi-DOTATATE. Pharmacokinetics and dosimetry of 213Bi-DOTATATE was determined in mice, in combination with renal protection. A dose escalation study with 213Bi-DOTATATE was performed to determine the maximum tolerated dose (MTD) with and without pre-administration of l-lysine as for renal protection. Neutrophil gelatinase-associated lipocalin (NGAL) served as renal biomarker to determine kidney injury. Results The maximum mean radiation absorbed tumor dose occurred at 0.03 nmol and the minimum at 3 nmol. Similar mean radiation absorbed tumor doses were determined for 0.1 and 0.3 nmol with a mean radiation absorbed dose of approximately 0.5 Gy/MBq 213Bi-DOTATATE. The optimal mass of injected peptide was found to be 0.3 nmol. Tumor uptake was similar for 111In-DOTATATE and 213Bi-DOTATATE at 0.3 nmol peptide. Lysine reduced the renal uptake of 213Bi-DOTATATE by 50% with no effect on the tumor uptake. The MTD was <13.0±1.6 MBq in absence of l-lysine and 21.7±1.9 MBq with l-lysine renal protection, both imparting an LD50 mean renal radiation absorbed dose of 20 Gy. A correlation was found between the amount of injected radioactivity and NGAL levels. Conclusions The therapeutic potential of 213Bi-DOTATATE was illustrated by significantly decreased tumor burden and improved overall survival. Renal protection with l-lysine immediately prior to TAT with 213Bi-DOTATATE prolonged survival providing substantial evidence for pharmacological nephron blockade to mitigate nephrotoxicity.
Recent clinical studies implicate the role of G protein-coupled estrogen receptor, GPR30, in aggressive forms of breast, ovarian, and endometrial cancers. However, the functional role of GPR30 at ...cellular and molecular levels remains less clear and controversial, particularly its subcellular location. The primary objective of this study was to develop radiolabeled neutral and charged GPR30-targeted nonsteroidal analogues to understand the influence of ligand charge on cell binding, cellular permeability, and in vivo tumor imaging. Therefore, we developed a series of GPR30-targeted 111/113In(III)-labeled analogues using macrocyclic and acyclic polyamino-polycarboxylate chelate designs that would render either a net negative or neutral charge. In vitro biological evaluations were performed to determine the role of negatively charged analogues on receptor binding and activation using calcium mobilization and phosphoinositide 3-kinase assays. In vivo evaluations were performed on GPR30-expressing human endometrial Hec50 tumor-bearing mice to characterize the biodistribution and potential application of GPR30-targeted imaging agents for translational research. In vitro functional assays revealed an effect of charge, such that only the neutral analogue activated GPR30-mediated rapid signaling pathways. These observations are consistent with expectations for initial rates of membrane permeability and suggest an intracellular rather than the cell surface location of functional receptor. In vivo studies revealed receptor-mediated uptake of the radiotracer in target organs and tumors; however, further structural modifications will be required for the development of future generations of GPR30-targeted imaging agents with enhanced metabolic properties and decreased nonspecific localization to the intestines.
Recent clinical studies implicate the role of G protein-coupled estrogen receptor, GPR30 in aggressive forms of breast, ovarian and endometrial cancers. However, the functional role of GPR30 at ...cellular and molecular level remains less clear and controversial, particularly its subcellular location. The primary objective of this study was to develop radiolabeled neutral and charged GPR30-targeted non-steroidal analogues to understand the influence of ligand charge on cell binding, cellular permeability and
in vivo
tumor imaging. Therefore, we developed a series of GPR30-targeted
111/113
In(III)-labeled analogues using macrocyclic and acyclic polyamino-polycarboxylate chelate designs that would render either a net negative or neutral charge.
In vitro
biological evaluations were performed to determine the role of negatively charged analogs on receptor binding and activation using calcium mobilization and phosphoinositide 3-kinase assays.
In vivo
evaluations were performed on GPR30-expressing human endometrial Hec50 tumor-bearing mice to characterize the biodistribution and potential application of GPR30-targeted imaging agents for translational research.
In vitro
functional assays revealed an effect of charge, such that only the neutral analogue activated GPR30-mediated rapid signaling pathways. These observations are consistent with expectations for initial rates of membrane permeability and suggest an intracellular rather than the cell surface location of functional receptor.
In vivo
studies revealed receptor-mediated uptake of the radiotracer in target organs and tumors; however, further structural modifications will be required for the development of future generations of GPR30-targeted imaging agents with enhanced metabolic properties and decreased non-specific localization to the intestines.
Breast and endometrial cancers are the most common invasive malignancies in women, with more than 217,000 new diagnoses per year in the United States. These cancers are often classified into 2 ...subtypes based on the expression of the classical estrogen receptor. In this study, we describe a new structural class of neutraf tridentate ^sup 99m^Tc(I)-estradiol-pyridin-2-yl hydrazine derivatives for potential use in breast and endometrial cancer imaging. Methods: The ^sup 99m^Tc(I)-estradiol-pyridin-2-yl hydrazine derivative was synthesized via the Sonogashira cross-coupling reaction and radiolabeled via the tricarbonyl approach. Radiochemical purity was assessed by high-performance liquid chromatography. Cell-binding studies were performed with human breast adenocarcinoma MCF-7 cells. The in vivo biodistribution of the ^sup 99m^Tc(I) derivative was evaluated in virgin female C57BL/6 mice in defined phases of the estrous cycle. Biodistribution and SPECT/CT studies were performed with mice bearing MCF-7 and primary human endometrial tumors. Results: Radiochemical analysis demonstrated that the postpurification purity of the ^sup 99m^Tc(I)-estradiol-pyridin-2-yl hydrazine derivative was ≥95%, with a specific activity of ^sup 99m^Tc of 47.5 TBq/mmol. Cell-binding studies yielded a dissociation constant (mean ± SEM) of 11 ± 1.5 nM. In vivo studies revealed that receptor-mediated uptake was present in all phases of the estrous cycle in reproductive organs and mammary glands but was highest during the diestrous phase of the estrous cycle. Despite high nonspecific uptake in the liver, significant receptor-mediated uptake was observed in target tissues and estrogen receptor-expressing tumors (0.67% for MCF-7 tumors and 0.77% for endometrial tumors). Tumor uptake was reduced by approximately 50% on coinjection with 17β-estradiol. Conclusion: We have characterized a novel neutral tridentate ^sup 99m^Tc(I)-estradiol-pyridin-2-yl hydrazine derivative for potential use in breast and endometrial cancer imaging. This study represents the first step on a path toward the design of estrogen-based Tc-labeled tracers with improved targeting and SPECT imaging characteristics. PUBLICATION ABSTRACT
PDF
