Célia Fernandes

[(Cp-R)M(CO)3] (M=Re or 99mTc) Arylsulfonamide, Arylsulfamide, and Arylsulfamate Conjugates for Selective Targeting of Human Carbonic Anhydrase IX†

Enhanced receptor selectivity: carbonic anhydrase inhibitors are relevant for both cancer diagnosis and therapy. Combining non-radioactive Re compounds with their radioactive (99m)Tc homologs enables the use of identical molecules for therapy and imaging (theragnostic). The syntheses and in vitro evaluation of [(Cp-R)M(CO)(3)] (Cp=cyclopentadienyl, M=Re, (99m)Tc) with R being a highly potent carbonic-anhydrase-targeting vector is reported.

Tris(pyrazolyl)methane 99mTc tricarbonyl complexes for myocardial imaging

Novel ether-containing tris(pyrazolyl)methane chelators stabilize thefac-[99mTc(CO)3]+ moiety providing complexes with significant, fast and stable heart uptake, together with a extremely fast liver clearance.

Preparation and biological evaluation of cyclopentadienyl-based 99mTc-complexes [(Cp-R)99mTc(CO)3] mimicking benzamides for malignant melanoma targeting

The biological evaluation of half-sandwich (99m)Tc-complexes that surrogate iodobenzamide with a high affinity for melanin tumor tissue is described. We have synthesized via retro Diels-Alder reaction two models of (99m)Tc complexes which possess the piano stool [Cp(99m)Tc(CO)(3)] motif instead of a phenyl ring as in the original iodobenzamide (123)I-N-(N-benzylpiperidin-4-yl)-2-iodobenzamide (2-IBP) and N-(2-diethylaminoethyl)-4-iodobenzamide (BZA). Diels-Alder products 2a-b (HCp-CONHR)(2) (2a, R=2-diethylaminoethyl; 2b, R=benzylpiperidin-4-yl) were prepared and reacted with fac-[(99m)Tc(H(2)O)(3)(CO)(3))](+) 1 in water to produce the corresponding (99m)Tc complexes [(2a)(99m)Tc(CO)(3))] 4a and [(2b)(99m)Tc(CO)(3))] 4b. The structures of the (99m)Tc complexes on the no-carrier-added level have been confirmed by chromatographic comparison with the corresponding rhenium complexes 3a and 3b, macroscopically characterized by IR, NMR, ESI-MS and X-ray crystallography for 3a [triclinic, P-1, a=7.3518(1) A, b=8.0309(2) A, c=17.5536(3) A, alpha=99.1260(5) degrees, beta=90.4215(14) degree , gamma=117.0187(11) degrees]. The radioconjugate 4b showed good in vitro stability. In murine melanoma B16F1 cells, significant cellular uptake (43.9% of the total applied activity) was attained after 4 h at 37 degrees C with about 50% of the cell-associated radioactivity being internalized in the cells (22% of the applied activity). Furthermore, in melanoma-bearing C57BL6 mice, tumor uptake values of 3.39+/-0.50 %ID g(-1) and 3.21+/-0.26 %ID g(-1) at 1 and 4 h postinjection, respectively, were observed indicating a good retention of 4b in the tumor.

Rapid hepatic clearance of 99mTc-TMEOP: a new candidate for myocardial perfusion imaging

BACKGROUND (99m)Tc labeled radiotracers used in clinical practice lack the perfect characteristics for myocardial perfusion imaging. In particular, the high liver uptake can interfere in the interpretation of the inferior myocardial wall. Within the tricarbonyl approach, we used tris(pyrazolyl)methane (99m)Tc organometallic complexes as a lead structure. Herein we present the production, in vivo and in vitro metabolic studies in rats and the first in vivo biodistribution in rats for tri-methoxy-tris-pyrazolyl-(99m)Tc-(CO)(3) ((99m)Tc-TMEOP), compared with (99m)Tc-sestamibi and (99m)Tc-tetrofosmin. METHODS The chemical identity of (99m)Tc-TMEOP was characterized by RP-HPLC. The octanol-water partition coefficient was determined under physiological conditions. In vitro stability and protein binding were determined using RP-HPLC. In vivo stability was determined in blood, heart, liver and kidney homogenates, intestine and urine using RP-HPLC. In vivo biodistribution was determined using dynamic planar acquisitions. Pinhole gated SPECT images were performed in other animals. Cardiac, liver and lung uptake were expressed as differential uptake ratios by drawing regions of interest in the organs of interest and around the total body. Heart-liver and heart-lung ratios were derived. Cardiac uptake was also expressed as percentage of injected activity. SPECT images were processed to determine the heart-liver ratio on SPECT images, to compare functional parameters between different tracers and to visualize homogeneous intracardiac tracer distribution. RESULTS (99m)Tc-TMEOP is a moderately lipophilic cation, is stable and does not undergo any transformation in vitro. (99m)Tc-TMEOP also shows a high in vivo stability. In vivo imaging shows liver kinetics faster than those of (99m)Tc-sestamibi and (99m)Tc-tetrofosmin. Cardiac uptake and functional analysis of pinhole gated SPECT data are comparable to those of (99m)Tc-sestamibi and (99m)Tc-tetrofosmin. CONCLUSION Although (99m)Tc-TMEOP shows a cardiac uptake between those of (99m)Tc-sestamibi and (99m)Tc-tetrofosmin, a better heart-liver ratio is obtained due to the faster liver washout. These results suggest possible faster cardiac perfusion imaging using (99m)Tc-TMEOP without liver activity interference.

Nuclear Targeting with an Auger Electron Emitter Potentiates the Action of a Widely Used Antineoplastic Drug

We present the combination of the clinically well-proven chemotherapeutic agent, Doxorubicin, and (99m)Tc, an Auger and internal conversion electron emitter, into a dual-action agent for therapy. Chemical conjugation of Doxorubicin to (99m)Tc afforded a construct which autonomously ferries a radioactive payload into the cell nucleus. At this site, damage is exerted by dose deposition from Auger radiation. The (99m)Tc-conjugate exhibited a dose-dependent inhibition of survival in a selected panel of cancer cells and an in vivo study in healthy mice evidenced a biodistribution which is comparable to that of the parent drug. The homologous Rhenium conjugate was found to effectively bind to DNA, inhibited human Topoisomerase II, and exhibited cytotoxicity in vitro. The collective in vitro and in vivo data demonstrate that the presented metallo-conjugates closely mimic native Doxorubicin.

Studies of the myocardial uptake and excretion mechanisms of a novel 99mTc heart perfusion agent

INTRODUCTION (99m)Tc-TMEOP is a novel heart perfusion radiotracer exhibiting high initial and persistent heart uptake associated with rapid blood and liver clearance. This study aimed at determining the mechanisms of myocardial localization and fast liver clearance of (99m)Tc-TMEOP. METHODS Subcellular distribution of (99m)Tc-TMEOP was determined in excised rat heart tissue by differential centrifugation. The effect of cyclosporin A on the pharmacokinetic behaviour of (99m)Tc-TMEOP was evaluated by both ex vivo biodistribution and in vivo planar imaging studies. RESULTS Subcellular distribution studies showed that more than 73% of (99m)Tc-TMEOP was associated with the mitochondrial fraction. Comparison with subcellular distribution of (99m)Tc-sestamibi showed no significant difference in the mitochondrial accumulation between the two tracers. Biodistribution studies in the presence of cyclosporin A revealed an increase in kidneys and liver uptake of (99m)Tc-TMEOP, suggesting the involvement of multidrug resistance transporters in determining its pharmacokinetic profile. CONCLUSIONS The heart uptake mechanism of (99m)Tc-TMEOP is similar to that of the other reported monocationic (99m)Tc cardiac agents and is associated with its accumulation in the mitochondria. Cyclosporin A studies indicate that the fast liver and kidney clearance kinetics is mediated by P-glycoprotein (Pgp), supporting the potential interest of this radiotracer for imaging Pgp function associated with multidrug-resistant tumours.

Radiohalogenated 4-anilinoquinazoline-based EGFR-TK inhibitors as potential cancer imaging agents.

INTRODUCTION The overexpression of epidermal growth factor receptor (EGFR) in tumors underlines the recent interest in EGFR as attractive target for the development of new cancer imaging agents. EGFR-tyrosine kinase inhibitors (EGFR-TKIs) based on the anilinoquinazoline scaffold have been explored as potential probes for EGFR imaging. However, up to now, no optimal radiotracer is available. Herein, we report the synthesis and biological evaluation of three novel halogenated 6-substituted 4-anilinoquinazoline based EGFR-TKIs. Radiosynthesis ((125)I and (18)F) of the corresponding analogues was also performed. METHODS 6a, 6b and 8 were obtained by reaction of 6-amino-4-anilinoquinazoline (5) with 3-/4-iodobenzoyl and 4-fluorobenzoyl chlorides. Inhibition of EGFR autophosphorylation and A431 cellular proliferation were assessed by Western blot and MTT assays. (125)I-anilinoquinazolines [(125)I]6a/b were prepared via destannylation of the corresponding tributylstannyl precursors with [(125)I]NaI. Cellular uptake studies were conducted in A431 cells. Optimization of the radiosynthesis of the (18)F-anilinoquinazoline [(18)F]8 was attempted by nucleophilic substitution of the trimethylammonium- and nitro-6-substituted 4-anilinoquinazoline precursors. RESULTS 6a, 6b and 8 were synthesized in high chemical yield. All of them are inhibitors of EGFR autophosphorylation (0.1<IC(50)<1 μM) and A431 cell proliferation (IC(50)<3.5 μM). [(125)I]6a/b, obtained in high radiochemical purity and specific activity, were highly taken up by A431 cells. Biodistribution profile in mice indicated fast blood clearance and hepatobiliary excretion. Despite all attempts, [(18)F]8 was only formed in 4% yield, hampering further biological evaluation. CONCLUSIONS This study suggests that these quinazoline derivatives can act as EGFR-TKI, warranting further modifications in the chemical structure in order to be explored as potential molecular imaging agents for single photon emission computerized tomography and positron emission tomography.

Silylated mixed-ligand rhenium complexes with the [PNS/S] donor atom set

Abstract New oxorhenium complexes with 2-(diphenylphosphanyl)- N -(2-thioethyl)benzamide (H 2 PNS) and trimethyl-, triethyl- and triphenyl-hydroxyl silylated monodentate thiols are reported. These new complexes have been prepared by reacting [N n Bu 4 ][Re(O)Cl 4 ] with the tridentate H 2 PNS and the corresponding silylated thiol at room temperature. The characterization of the complexes involved elemental analysis, 31 P and 1 H NMR spectroscopies and X-ray crystallographic analysis for the triethyl-silylated Re complex.

Novel Heterobimetallic Radiotheranostic: Preparation, Activity, and Biodistribution

A novel RuII(arene) theranostic complex is presented. It is based on a 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid macrocycle bearing a triarylphosphine and can be tracked in vivo by using the γ emission of 153Sm atoms. Notably, the heteroditopic ligand can be selectively metalated with ruthenium at the phosphorus atom despite the presence of other functionalities that are prone to metal coordination. Subsequent labeling with radionuclides such as 153Sm can then be performed easily. The resulting heterobimetallic complex exhibits favorable solubility and stability properties in biologically relevant media. It also shows in vitro cytotoxicity in line with that expected for this type of metallodrug, and is nontoxic to the organism as a whole. As a proof of concept, initial studies in healthy mice were performed to obtain information about the uptake, biodistribution, and excretion of the radiolabeled complex.

Novel (188)Re multi-functional bone-seeking compounds: Synthesis, biological and radiotoxic effects in metastatic breast cancer cells.

INTRODUCTION Radiolabeled bisphosphonates (BPs) have been used for bone imaging and delivery of β(-) emitting radionuclides for bone pain palliation. As a β(-) emitter, (188)Re has been considered particularly promising for bone metastases therapy. Aimed at finding innovative bone-seeking agents for systemic radiotherapy of bone metastases, we describe herein novel organometallic compounds of the type fac-[(188)Re(CO)3(k(3)-L)], (L=BP-containing chelator), their in vitro and in vivo stability, and their cellular damage in MDAMB231 cells, a metastatic breast cancer cell line. METHODS After synthesis and characterization of the novel organometallic compounds of the type fac-[(188)Re(CO)3(k(3)-L)] their radiochemical purity and in vitro stability was assessed by HPLC. In vivo stability and pharmacokinetic profile were evaluated in mice and the radiocytotoxic activity and DNA damage were assessed by MTT assay and by the cytokinesis-block micronucleus (CBMN) assay, respectively. RESULTS Among all complexes, (188)Re3 was obtained with high radiochemical purity (>95%) and high specific activity and presented high in vitro and in vivo stability. Biodistribution studies of (188)Re3 in Balb/c mice showed fast blood clearance, high bone uptake (16.1 ± 3.3% IA/g organ, 1h p.i.) and high bone-to-blood and bone-to-muscle radioactivity ratios, indicating that it is able to deliver radiation to bone in a very selective way. The radiocytotoxic effect elicited by (188)Re3 in the MDAMB231 cells was dependent on its concentration, and was higher than that induced by identical concentrations of [(188)ReO4](-). Additionally, (188)Re3 elicited morphological changes in the cells and induced DNA damage by the increased number of MN observed. CONCLUSION Altogether, our results demonstrate that (188)Re3 could be considered an attractive candidate for further preclinical evaluation for systemic radionuclide therapy of bone metastases considering its ability to deliver radiation to bone in a very selective way and to induce radiation damage.