Technetium glucose complexes as potential cancer imaging agents

Phase I Clinical Trial Using [99mTc]Tc-1-thio-D-glucose for Diagnosis of Lymphoma Patients

Similar to [¹⁸F]-FDG, [^99mTc]Tc-1-thio-D-glucose ([^99mTc]Tc-TG) also binds to GLUT receptors. The aim of this Phase I study was to evaluate the safety, biodistribution and dosimetry of [^99mTc]Tc-TG. Twelve lymphoma patients were injected with 729 ± 102 MBq [^99mTc]Tc-TG. Whole-body planar imaging was performed in 10 patients at 2, 4, 6 and 24 h after injection. In all 12 patients, SPECT/CT (at 2 h) and SPECT (at 4 and 6 h) imaging was performed. Vital signs and possible side effects were monitored during imaging and up to 7 days after injection. [^99mTc]Tc-TG injections were well-tolerated and no side effects or alterations in blood and urine analyses data were observed. The highest absorbed dose was in the kidneys and urinary bladder wall, followed by the adrenals, prostate, bone marrow, lungs, myocardium, ovaries, uterus, liver and gall bladder wall. [^99mTc]Tc-TG SPECT/CT revealed foci of high activity uptake in the lymph nodes of all nine patients with known nodal lesions. Extranodal lesions were detected in all nine cases. In one patient, a lesion in the humerus head, which was not detected by CT, was visualized using [^99mTc]Tc-TG. Potentially, [^99mTc]Tc-TG can be considered as an additional diagnostic method for imaging GLUT receptors in lymphoma patients.

99mTc-CN7DG: A Highly Expected SPECT Imaging Agent of Cancer with Satisfactory Tumor Uptake and Tumor-to-Nontarget Ratios

A novel glucose derivative (CN7DG) possessing an isonitrile as a coordinating group was synthesized, and ^99mTc-CN7DG, which was expected to be a powerful tumor imaging agent for SPECT, was prepared in a kit by the reaction of CN7DG with SnCl₂·2H₂O and ^99mTcO₄^-. ^99mTc-CN7DG exhibited good stability and was transported via glucose transporters. Biodistribution results in mice bearing A549 tumor models showed that ^99mTc-CN7DG had a higher uptake at the tumor sites and better tumor/blood and tumor/muscle ratios than did [¹⁸F]FDG and ^99mTc-CN5DG. SPECT/CT imaging studies showed obvious accumulation in tumor sites, suggesting that ^99mTc-CN7DG is a promising candidate for tumor imaging. Because ^99mTc and ¹⁸⁸Re stand for a "theranostic pair", ¹⁸⁸Re-CN7DG is expected to be prepared as a promising agent for tumor therapy.

Single Photon Emission Computed Tomography Tracer

Single photon emission computed tomography (SPECT) is the state-of-the-art imaging modality in nuclear medicine despite the fact that only a few new SPECT tracers have become available in the past 20 years. Critical for the future success of SPECT is the design of new and specific tracers for the detection, localization, and staging of a disease and for monitoring therapy. The utility of SPECT imaging to address oncologic questions is dependent on radiotracers that ideally exhibit excellent tissue penetration, high affinity to the tumor-associated target structure, specific uptake and retention in the malignant lesions, and rapid clearance from non-targeted tissues and organs. In general, a target-specific SPECT radiopharmaceutical can be divided into two main parts: a targeting biomolecule (e.g., peptide, antibody fragment) and a γ-radiation-emitting radionuclide (e.g., ^99mTc, ¹²³I). If radiometals are used as the radiation source, a bifunctional chelator is needed to link the radioisotope to the targeting entity. In a rational SPECT tracer design, these single components have to be critically evaluated in order to achieve a balance among the demands for adequate target binding, and a rapid clearance of the radiotracer. The focus of this chapter is to depict recent developments of tumor-targeted SPECT radiotracers for imaging of cancer diseases. Possibilities for optimization of tracer design and potential causes for design failure are discussed and highlighted with selected examples.

Synthesis and preliminary evaluation of a 99mTc labelled deoxyglucose complex {[99mTc]DTPA-bis(DG)} as a potential SPECT based probe for tumor imaging

[^99mTc]DTPA-bis(DG): a potent tumor imaging probe.

Novel 99mTc-Labeled Glucose Derivative for Single Photon Emission Computed Tomography: A Promising Tumor Imaging Agent

In this study, a d-glucosamine derivative with an isonitrile group (CN5DG) was synthesized and it was chosen to coordinate with ^99mTc for preparing ^99mTc-CN5DG. ^99mTc-CN5DG could be readily obtained with high radiochemical purity (>95%) and had great in vitro stability and metabolic stability in urine. The radiotracer demonstrated a positive response to the administration of glucose and insulin in S180 and A549 tumor cells in vitro, suggesting the mechanism of ^99mTc-CN5DG into tumor cells was related to glucose transporters. Biodistribution studies in mice bearing A549 xenografts showed ^99mTc-CN5DG had a high tumor uptake and high tumor-to-background ratios. SPECT/CT images further supported its ability for tumor imaging. As a cheap, conveniently made and widely available probe, ^99mTc-CN5DG would become a potential "working horse" and be a breakthrough in ^99mTc-labeled radiopharmaceuticals for tumor detection.

Synthesis and biodistribution of novel 99mTcN complexes of glucose dithiocarbamate as potential probes for tumor imaging

^99mTcN-3b can be prepared from a kit without the need for purification and would be a promising tumor imaging agent.