Christiane Contino-Pépin

Preliminary biological evaluations of new thalidomide analogues for multiple sclerosis application

The present work deals with the synthesis of a new series of thalidomide derivatives for therapeutic applications. These compounds were evaluated in vitro on a human endothelial cell line EA.hy926 for their antiproliferative potential and in vivo on an experimental animal multiple sclerosis model called EAE as angiogenesis inhibitors. The preliminary results obtained on EAE assays seem to validate that anti-angiogenesis compounds could be promising tools for the treatment of MS.

Synthesis and preliminary biological assessments of RGD bearing biocompatible telomers

Work reported herein deals with the synthesis and preliminary biological assessments of a new class of biocompatible telomeric carriers bearing peptidic RGDSK sequences as tumor cell targeting and tyrosine moieties labelled with 125I as in vivo probe. The radioactivity levels obtained in several tissues, after the intravenous injections of these telomers in mice bearing grafted B16 syngenic melanoma showed that the addition of a RGD residue to a telomeric structure confers it an increased affinity for the highly vascularized zone surrounding the tumor.

Targeting Vascular Changes in Lesions in Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis

What is the origin of the complex vascular changes that exist in the CNS lesions of Multiple Sclerosis (MS)? From the beginning of the study of the pathological changes in MS in the 19th century, lesions were seen to be associated with veins. On a microscopic level, there have been numerous pathological changes to these vessels including altered structure and permeability, fibrinolysis, iron-related alterations and collagen deposition. Vascular changes in inflammatory conditions outside the CNS are well documented and we hypothesize that angiogenesis (the generation of new blood vessels from existing) is an integral process of lesion development and spread in MS. We demonstrated similar vascular abnormalities in MS and in the animal model, EAE. We measured the increase in angiogenesis-related genes in EAE and review herein the effectiveness of chemical inhibitors of angiogenesis (SU5416, thalidomide and several derivatives). We postulate that interference with angiogenesis provides a suitable non-immunological target for investigation in MS.

Thalidomide Derivatives for the Treatment of Neuroinflammation

The precise mechanism‐of‐action of thalidomide remains uncertain and might differ between diseases and under different clinical condition. With implications in the treatment of a variety of inflammatory and autoimmune diseases, as well as for use as an anticancer agent, alone or in combination with established therapeutics, it is clear that thalidomide and its derivatives deserve further scrutiny. In particular, thalidomide was shown to be effective in a mouse model of multiple sclerosis (MS), an autoimmune inflammatory disorder, called experimental autoimmune encephalomyelitis (EAE). Herein, we describe the synthesis and preliminary biological evaluation of new macromolecular prodrugs of thalidomide bearing an aminoalkyl group on the phthalimide ring. The effectiveness of these compounds to limit EAE was investigated, and it was shown that, at 100 mg kg−1 thalidomide‐equivalent dose, they abrogated the clinical and pathological features of EAE.

Effect of Dimethyl Sulfoxide on the Binding of 1-Adamantane Carboxylic Acid to β- and γ-Cyclodextrins

Most therapeutic targets are proteins whose binding sites are hydrophobic cavities. For this reason, the majority of drugs under development are hydrophobic molecules exhibiting low solubility in water. To tackle this issue, a few percent of cosolvent, such as dimethyl sulfoxide (DMSO), is usually employed to increase drug solubility during the drug screening process. However, the few published studies dealing with the effect of adding DMSO showed that the affinity of hydrophobic ligands is systematically underestimated. To better understand the effect of DMSO, there is a need of studying its effect on a large range of systems. In this work, we used β- and γ-cyclodextrins (made of 6 and 7 α-d-glucopyranoside units, respectively) as models of hydrophobic cavities to investigate the effect of the addition 5% DMSO on the affinity of 1-adamantane carboxylic acid (ADA) to these cyclodextrins. The two systems differ by the size of the cyclodextrin cavity. The evaluation of binding constants was performed using ultrasound velocimetry, nuclear magnetic resonance spectroscopy, and molecular simulations. All techniques show that the presence of 5% DMSO does not significantly modify the affinity of ADA for γ-cyclodextrin, while the affinity is dramatically reduced for β-cyclodextrin. The bias induced by the presence of DMSO is thus more important when the ligand volume better fits the cyclodextrin cavity. Our work also suggests that free energy calculations provide a sound alternative to experimental techniques when dealing with poorly water-soluble drugs.

Molecular oxygen loading in candidate theranostic droplets stabilized with biocompatible fluorinated surfactants: Particle size effect and application to in situ 19F MRI mapping of oxygen partial pressure

OBJECTIVE Perfluorocarbon nano- and micron-sized emulsions are a new field of investigation in cancer treatment due to their ability to be used as imaging contrast agents, or as delivery vectors for pharmaceuticals. They also demonstrated capability to enhance the efficiency of high intensity focused ultrasound thermo-therapy. In the context of new biomedical applications we investigated perfluorooctyl bromide (PFOB) theranostic droplets using 19F NMR. Each droplet contains biocompatible fluorinated surfactants composed of a polar Tris(hydroxymethyl)aminomethane head unit and hydrophobic perfluorinated tail (abbreviated as F-TAC). The influence of the droplet size on the oxygen loading capacity was determined from longitudinal relaxation (T1) data of 19F NMR signal. MATERIAL AND METHODS Liquid PFOB and five samples of PFOB droplets of average diameter 0.177, 0.259, 1.43, 3.12 and 4.53 µm were tested with different oxygen levels. A dedicated gas exchange system was validated to maintain steady state oxygen concentrations, including a spatial gradient of oxygen concentration. A prototyped transmit-receive switchable 19F/1H quadrature coil was integrated on a 3 T clinical scanner. The coil is compatible with focused ultrasound sonication for future application. A spectroscopy FID inversion-recovery (IR) sequence was used to measure the T1 value per sample and per value of equilibrium oxygen pressure. Pixel wise, spatial T1 mapping was performed with magnetization prepared 2D gradient echo sequences in tissue mimicking gels doped with theranostic droplets. RESULTS Experimental data indicated that the longitudinal relaxation rate of 19F signal of the investigated theranostic droplets depended approximately linearly on the oxygen level and its slope decreased with the particle size according to a second order polynomial over the investigated range. This semi-empirical model was derived from general thermodynamics and weak electrostatic forces theory and fitted the experimental data within 0.75% precision. The capacity of oxygen transportation for the described theranostic droplets tended to that of pure PFOB, while micron-sized droplets lost up to 50% of this capacity. In a specific setup producing a steady state gradient of oxygen concentration, we demonstrated spatial mapping of oxygen pressure gradient of 6 kPa/mm with 1 mm in-plane resolution. CONCLUSION The size-tunable PFOB theranostic droplets stabilized with F-TAC surfactants could be characterized by 19F MRI in a clinical setup readily compatible with interventional in vivo studies under MR guidance. Current precision and spatial resolution of T1 mapping are promising. A potential challenge for further in vivo studies is the reduction of the imaging time.

Design and characterization of biocompatible perfluorocarbon nanodroplets for theragnostic application

We have developed stable emulsions (≥ 3 months) made of nanodroplets (nD) of perfluorocarbon (PFC) dispersed in water to serve as theragnostic agent. nD are stabilized by in house fluorinated surfactants, named FTAC, which chemical structure can be modified to tune their properties. We have characterized nD size distributions (mean diameters from 200 to 600 nm), density, adiabatic compressibility, interfacial tension. US properties of the emulsions have been investigated such as attenuation. Lastly, ultrasonic signals backscattered by nanoemulsions were studied and compared with water to extract signal to noise ratio (SNR), by emitting single negative pulses at ≈40 MHz. At similar mean/mode diameters, we showed a strong dependence in SNR values (i) with size distribution, altered by the nature of the surfactant or by a centrifugation/filtration process, (ii) with core nature, and (iii) with nD volume fraction. Besides, hydrophobic drugs such as a thalidomide derivative (with anti-angiogenic properties), have been encapsulated by addition of 10% of triacetin in the nD core. So as to study drug release from nD, a dedicated setup of US cavitation was designed. Cavitation was generated in controlled conditions using a 1 MHz focused transducer (US bursts: 12-22 MPa peak) in a thin wall container immersed in water which temperature and degassed level were kept constant. The generation of cavitation in nD solutions resulted in a strong and reproducible SNR decrease.