Nicolas Lepareur

188Re-loaded lipid nanocapsules as a promising radiopharmaceutical carrier for internal radiotherapy of malignant gliomas

PurposeLipid nanocapsules (LNC) entrapping lipophilic complexes of 188Re (188Re(S3CPh)2(S2CPh) [188Re-SSS]) were investigated as a novel radiopharmaceutical carrier for internal radiation therapy of malignant gliomas. The present study was designed to evaluate the efficacy of intra-cerebral administration of 188Re-SSS LNC by means of convection-enhanced delivery (CED) on a 9L rat brain tumour model.MethodsFemale Fischer rats with 9L glioma were treated with a single injection of 188Re-SSS LNC by CED 6days after cell implantation. Rats were put into random groups according to the dose infused: 12, 10, 8 and 3Gy in comparison with blank LNC, perrhenate solution (4Gy) and non-treated animals. The radionuclide brain retention level was evaluated by measuring 188Re elimination in faeces and urine over 72h after the CED injection. The therapeutic effect of 188Re-SSS LNC was assessed based on animal survival.ResultsCED of 188Re perrhenate solution resulted in rapid drug clearance with a brain T1/2 of 7h. In contrast, when administered in LNC, 188Re tissue retention was greatly prolonged, with only 10% of the injected dose being eliminated at 72h. Rat median survival was significantly improved for the group treated with 8Gy 188Re-SSS LNC compared to the control group and blank LNC-treated animals. The increase in the median survival time was about 80% compared to the control group; 33% of the animals were long-term survivors. The dose of 8Gy proved to be a very effective dose, between toxic (10–12Gy) and ineffective (3–4Gy) doses.ConclusionsThese findings show that CED of 188Re-loaded LNC is a safe and potent anti-tumour system for treating malignant gliomas. Our data are the first to show the in vivo efficacy of 188Re internal radiotherapy for the treatment of brain malignancy.

Tumor eradication in rat glioma and bypass of immunosuppressive barriers using internal radiation with (188)Re-lipid nanocapsules

To date, glioblastoma treatments have only been palliative. In this context, locoregional drug delivery strategies, which allow for blood--brain barrier bypass and reduced systemic toxicity, are of major significance. Recent progress in nanotechnology has led to the development of colloidal carriers of radiopharmaceutics, such as lipid nanocapsules loaded with rhenium-188 (LNC(188)Re-SSS) that are implanted in the brain. In our study, we demonstrated that fractionated internal radiation using LNC(188)Re-SSS triggered remarkable survival responses in a rat orthotopic glioma model (cure rates of 83%). We also highlighted the importance of the radioactivity activity gradient obtained by combining a simple stereotactic injection (SI) with convection-enhanced delivery (CED).We assumed that the immune system played a role in the treatments efficacy on account of the overproduction of peripheral cytokines, recruitment of immune cells to the tumor site, and memory response in long-term survivor animals. Hence, nanovectorized internal radiation therapy with activity gradients stimulating immune responses may represent a new and interesting alternative for the treatment of solid tumors such as glioblastomas.

188Re-SSS lipiodol: radiolabelling and biodistribution following injection into the hepatic artery of rats bearing hepatoma.

BackgroundAlthough intra-arterial radiation therapy with 131I-lipiodol is a useful therapeutic approach to the treatment of hepatocellular carcinoma, various disadvantages limit its use. AimTo describe the development of a method for the labelling of lipiodol with 188Re-SSS (188Re (S2CPh)(S3CPh)2 complex) and to investigate its biodistribution after injection into the hepatic artery of rats with hepatoma. Methods188Re-SSS lipiodol was obtained after dissolving a chelating agent, previously labelled with 188Re, in cold lipiodol. The radiochemical purity (RCP) of labelling was checked immediately. The 188Re-SSS lipiodol was injected into the hepatic artery of nine rats with a Novikoff hepatoma. They were sacrificed 1, 24 and 48 h after injection, and used for ex vivo counting. ResultsLabelling of 188Re-SSS lipiodol was achieved with a yield of 97.3±2.1%. The immediate RCP was 94.1±1.7%. Ex vivo counting confirmed a predominantly hepatic uptake, with a good tumoral retention of 188Re-SSS lipiodol, a weak pulmonary uptake and a very faint digestive uptake. The ‘tumour/non-tumoral liver’ ratio was high at 1, 24 and 48 h after injection (2.9±1.5, 4.1±4.1 and 4.1±0.7, respectively). ConclusionsUsing the method described here, 188Re-SSS lipiodol can be obtained with a very high yield and a satisfactory RCP. The biodistribution in rats with hepatoma indicates a good tumoral retention of 188Re-SSS lipiodol associated with a predominant hepatic uptake, a weak pulmonary uptake and a very faint digestive uptake. This product should be considered for intra-arterial radiation therapy in human hepatoma.

Development of 99mTc labelled Lipiodol: biodistribution following injection into the hepatic artery of the healthy pig

BackgroundWe develop a method for the radiolabelling of Lipiodol with 99mTc, using a lipophilic complex, [99mTc-(S2CPh)(S3Ph)2], dissolved in Lipiodol (99mTc-SSS Lipiodol). ResultsThe labelling yield is high (96±0.8%), and the radiochemical purity satisfactory (92±2.6%). This labelling is reproducible and stable for up to 24 h in vitro. Studies carried out after injection into the hepatic artery of the healthy pig show that the biodistribution of 99mTc-SSS Lipiodol is comparable with that observed for 188Re Lipiodol. Materials and methodsThe 99mTc-SSS lipiodol was obtained after dissolving a chelating agent, previously labelled with 99mTc, in cold lipiodol. The radiochemical purity (RCP) of the labelling was checked immediately and at 24 h. The 99mTc-SSS lipiodol was injected into the hepatic artery of four healthy pigs for an ex-vivo biodistribution study. An autoradiographic study was performed in two cases. ConclusionsApart from the specific interest of a Lipiodol-bearing technetiated agent for carrying out dosimetric studies, the labelling of Lipiodol with 99mTc is a preliminary step towards the use of radiolabelling with the 188Re analogue.

(188)Re-SSS/Lipiodol: Development of a Potential Treatment for HCC from Bench to Bedside.

Hepatocellular carcinoma (HCC) is the 5th most common tumour worldwide and has a dark prognosis. For nonoperable cases, metabolic radiotherapy with Lipiodol labelled with β-emitters is a promising therapeutic option. The Comprehensive Cancer Centre Eugène Marquis and the National Graduate School of Chemistry of Rennes (ENSCR) have jointly developed a stable and efficient labelling of Lipiodol with rhenium-188 (Eβmax = 2.1 MeV) for the treatment of HCC. The major “milestones” of this development, from the first syntheses to the recent first injection in man, are described.

Increased Lipiodol uptake in hepatocellular carcinoma possibly due to increased membrane fluidity by dexamethasone and tamoxifen

INTRODUCTION Lipiodol is used as a vector for chemoembolization or internal radiotherapy in unresectable hepatocellular carcinomas (HCCs). The aim of this study is to improve the tumoral uptake of Lipiodol by modulating membrane fluidizing agents to optimize the effectiveness of Lipiodol vectorized therapy. METHODS The effect of dexamethasone and tamoxifen on membrane fluidity was studied in vitro by electron paramagnetic resonance applied to rat hepatocarcinoma cell line N1S1. The tumoral uptake of Lipiodol was studied in vivo on rats with HCC, which had been previously treated by dexamethasone and/or tamoxifen, after intra-arterial administration of (99m)Tc-SSS-Lipiodol. RESULTS The two molecules studied here exhibit a fluidizing effect in vitro which appears dependent on time and dose, with a maximum fluidity obtained after 1 hr at concentrations of 20 μM for dexamethasone and 200 nM for tamoxifen. In vivo, while the use of dexamethasone or tamoxifen alone tends to lead to increased tumoral uptake of Lipiodol, this effect does not reach levels of significance. On the other hand, there is a significant increase in the tumoral uptake of (99m)Tc-SSS-Lipiodol in rats pretreated by both dexamethasone and tamoxifen, with a tumoral uptake (expressed in % of injected activity per g of tumor) of 13.57 ± 3.65% after treatment, as against 9.45 ± 4.44% without treatment (P<.05). CONCLUSIONS Dexamethasone and tamoxifen fluidify the N1S1 cells membrane, leading to an increase in the tumoral uptake of Lipiodol. These drugs could be combined with chemo-Lipiodol-embolization or radiolabeled Lipiodol, with a view to improving the effectiveness of HCCs therapy.

Automation of labelling of Lipiodol with high-activity generator-produced 188Re.

This work describes optimisation of the kit formulation for labelling of Lipiodol with high-activity generator-produced rhenium-188. Radiochemical purity (RCP) was 92.52±2.3% and extraction yield was 98.56±1.2%. The synthesis has been automated with a TADDEO module (Comecer) giving a mean final yield of 52.68±9.6%, and reducing radiation burden to the radiochemist by 80%. Radiolabelled Lipiodol ((188)Re-SSS/Lipiodol) is stable for at least 7 days (RCP=91.07±0.9%).

Optimization of Hepatocarcinoma Uptake with Radiolabeled Lipiodol: Development of New Lipiodol Formulations with Increased Viscosity

The aim of this study was to develop new Lipiodol formulations with increased viscosities to augment Lipiodol embolic effect and optimize efficiency of radiolabeled Lipiodol in hepatocarcinoma treatments. New Lipiodol formulations consist of Lipiodol mixtures with different stearic acid concentrations (0.8%, 1.3%, and 1.8%). These formulations were fully characterized in vitro (viscosity, rheologic profiles) and labeled with 99mTc. Their viscosities at 20°C are 54, 60, and 67cP respectively, versus 45cP for Lipiodol ultra-fluide. Second, their biodistribution profiles were studied in vivo, at 24 and 72 hours, in hepatoma-bearing rats, and compared to control group (99mTc-Lipiodol). Biodistribution at 24 hours show a Gaussian tumor uptake profile with a maximum obtained with 1.3% stearic acid, and a tumor uptake superior to control group (+67%) (p<0.05). At 72 hours, optimal tumor uptake is reached with the 0.8% formulation, with 89% increase compared with control group (p<0.05). Moreover, we show a tendency to the decrease of pulmonary uptake for the new formulations at 24 hours and 72 hours. These results suggest a correlation between viscosity and Lipiodol tumor uptake. The new 0.8% stearic acid/Lipiodol formulation appears to be the optimized formulation for Lipiodol treatments of hepatocarcinoma, since it leads to a significant increase of tumor uptake at 72 hours and possibly to a decrease of undesirable pulmonary effects.

Effect of stabilized iodized oil emulsion on experimentally induced hepatocellular carcinoma in rats.

PURPOSE Previous studies have shown that the use of Lipiodol UltraFluid (LUF) emulsified with water leads to an increase in the tumoral uptake of iodine I 131-labeled LUF and reduced pulmonary uptake. Although emulsions containing LUF are currently used for chemoembolization of hepatocellular carcinomas (HCCs), this approach is impossible with intraarterial radiation therapy (RT) because of the problems of radiation protection linked to instability of the emulsions. The aims of this study were to develop stabilized emulsions of radiolabeled LUF of different particle sizes and viscosities and to study its biodistribution in rats with HCC. MATERIALS AND METHODS An emulsifier made of polyethylene glycol and hydrogenated castor oil was used to stabilize emulsions containing water and technetium Tc 99m-labeled Super Six Sulfur LUF. The various emulsions were injected in the hepatic arteries of rats with HCC. Twenty-four hours after injection, the rats were killed and the liver, tumor, and lungs were removed to perform ex-vivo gamma-counting to quantify tumoral, hepatic, and pulmonary uptake. RESULTS Emulsions of oil in water and water in oil of different viscosities (0.68-1.06 Pa.S) and particle size distributions (21-45 mum) were prepared and kept stable for more than 24 hours. Whatever the type of emulsion, the observed effect on tumoral uptake was the opposite of that expected. Indeed, a decrease in tumoral activity was observed (P < .05 in three of five cases) and a tendency toward increased pulmonary activity was observed (P < .05 in two of five cases) rather than any significant decrease. CONCLUSIONS This study made it possible to develop emulsions of radiolabeled iodized oil that remain stable for more than 24 hours. However, studies of biodistribution in rats with HCC failed to demonstrate any improvement in tumoral targeting, but rather showed a decrease in tumoral uptake that renders this approach impractical for intraarterial radiolabeled iodized oil RT as well as for intraarterial iodized oil chemoembolization. These results may possibly be explained by the use of an emulsifier containing lipophilic and hydrophilic components that modify the properties of LUF.

Syntheses and reactivity of ‘sulfur rich’ Re(III) and Tc(III) complexes containing trithioperoxybenzoate, dithiobenzoate and dithiocarbamate ligands

Reduction-substitution reactions of [M(O)Cl(4)](-)(M=Re, (99)Tc) precursors with an excess of substituted dithiobenzoate ligands (R-PhCS(2))(-) in dichloromethane/methanol mixtures afford a series of six-coordinated neutral mixed-ligand complexes of the type M(III)(R-PhCS(3))(2)(R-PhCS(2))(M=Re; Rel--9; M=99)Tc; Tel--9). The coordination sphere is entirely filled by sulfur donor atoms, and the complexes adopt a distorted trigonal prismatic arrangement, as assessed by the X-ray crystal structure analysis of Re(4-Me-PhCS(3))(2)(4-Me-PhCS(2)), Re 2. These compounds show sharp proton and carbon NMR profiles, in agreement with the diamagnetism typical of low spin d(4) trigonal prismatic configurations. The red-ox processes involve reduction of the metal from Re(v) to Re(iii) and oxidation of dithiobenzoate to trithioperoxybenzoate. M2--9 complexes contain a substitution-inert [M(R-PhCS(3))(2)](+) moiety including the metal and two trithioperoxybenzoate fragments, while the third dithiobenzoate ligand is labile. The latter is efficiently replaced by reaction with better nucleophiles such as diethyldithiocarbamate giving a further class of mixed ligand complexes of the type M(III)(R-PhCS(3))(2)(Et(2)NCS(2))(M=Re; Re 10--18; M=(99)Tc; Tc--18), which retain the trigonal prismatic arrangement, as determined by the X-ray analyses of the representative compounds Re(PhCS(3))(2)(Et(2)NCS(2)), Re 10 and (99)Tc(PhCS(3))(2)(Et(2)NCS(2)), Tc 10.