Les maladies cardiovasculaires sont la première cause de mortalité dans le monde, et la maladie coronaire est responsable de la majorité de ces décès. L’infarctus du myocarde et l’AVC sont principalement causés par la rupture de plaques d’athérome vulnérables. Malgré les récentes avancées dans la prise en charge des patients, aucun outil non invasif n’est actuellement disponible en pratique clinique pour le diagnostic de ces lésions. Le laboratoire UMR_S1039 Radiopharmaceutiques Biocliniques a développé un agent d’imagerie innovant ciblant la molécule d’adhésion cellulaire VCAM-1, impliquée dans le processus inflammatoire qui caractérise les plaques vulnérables. 99mTc-cAbVCAM1-5 appartient à une nouvelle classe de radiotraceurs dérivés d’anticorps de camélidés possédant uniquement une chaine lourde dont le domaine variable est appelé nanobody. Les lésions athéromateuses aortiques ont été visualisées avec succès par imagerie non invasive (SPECT) chez un modèle de souris déficient pour le gène ApoE. L’objectif de ma thèse a été double : finaliser la caractérisation préclinique de cAbVCAM1-5 et transférer ce radiotraceur vers la clinique. Dans un premier temps, la sensibilité de 99mTc-cAbVCAM1-5 a été démontrée avec succès par l’utilisation de thérapies de référence (statine, ézétimibe). Ces résultats prometteurs nous ont permis d’évaluer le potentiel effet anti-athérogène de nouveaux agents thérapeutiques et d’initier le transfert en clinique de cet agent d’imagerie. cAbVCAM1-5 et l’intermédiaire de réaction utilisé pour son radiomarquage ont été produits selon les bonnes pratiques de fabrication (BPF). Ces deux produits ont été évalués et validés. De plus la méthode de radiomarquage a été optimisée dans la perspective de son transfert vers la clinique. L’étude de toxicité étendue à dose unique est en cours. A l’issue de cette thèse, le laboratoire INSERM U1039 dispose donc de tous les éléments nécessaires pour une demande d’autorisation de phase clinique I/IIa. / Cardiovascular diseases (CVD) are the leading causes of death worldwide, and Coronary Artery Disease (CAD) is responsible for the majority of CVD deaths. Myocardial infarction and stroke are mainly caused by the rupture of vulnerable atherosclerotic plaques. Despite recent advances in treatment and detection of CAD, no non-invasive tool is currently available for the diagnosis of vulnerable plaques. The laboratory UMR_S1039 Radiopharmaceutiques Biocliniques has recently developed a new radiotracer (99mTc-cAbVCAM1-5) targeted to the inflammatory marker Vascular Cell Adhesion Molecule 1 (VCAM-1) expressed in vulnerable plaques. 99mTc-cAbVCAM1-5 belongs to a new class of radiotracers derived from single domain antibodies (sdAb), or nanobodies, that are composed of the single variable domain of the heavy chain antibodies of camelidae. Aortic plaques have been successfully visualized noninvasively by SPECT in an Apolipoprotein E (ApoE) deficient mouse model of atherosclerosis. The objectives of my thesis were to complete the preclinical characterization of cAbVCAM1-5 and to transfer this innovative tool to the clinic. The sensitivity of 99mTc-cAbVCAM1-5 imaging has been successfully demonstrated using gold standard therapies (statin, ezetimibe). Those good results allowed us to employ this imaging agent for the evaluation of new therapeutics and to initiate the clinical translation of cAbVCAM1-5. The productions of cAbVCAM1-5 and of the tricarbonyl employed for its radiolabeling have been performed according to good manufacturing practices (GMP). Both products have been evaluated and validated. Furthermore, the radiolabeling method has been optimized to facilitate its clinical transfer. Single dose toxicity study is currently ongoing. At the end of this PhD fellowship, the U1039 Laboratory therefore possesses all required products and knowledge for the onset of a first in human clinical trial.

Atherosclerotic and restenotic lesions develop as a result of an excess inflammatory response to vascular injury. Glucocorticoid hormones have widely-recognised anti-inflammatory and anti-proliferative properties which appear to make them ideal candidates for inhibition of vascular lesion development. Indeed, administration of glucocorticoids to experimental animals does inhibit the growth of vascular lesions in some models. In addition, glucocorticoids are currently being trialled clinically as anti-restenotic agents. However, glucocorticoid excess in patients, either as a result of Cushing’s syndrome or chronic steroid therapy, is associated with enhanced CVD risk. Therefore, the effects of glucocorticoids on vascular lesion development remain imperfectly understood. The overall objective of these studies was to explore the influence of endogenous and exogenous glucocorticoids on vascular lesion development using murine models of atherosclerosis (ApoE-/- mice fed a “western” diet) and neointimal hyperplasia (wireinduced femoral artery injury). The work described in this thesis addresses the hypothesis that glucocorticoids are pro-atherogenic, yet anti-restenotic. Mice were bilaterally adrenalectomised to investigate the role of endogenous glucocorticoids on vascular lesion development. Removal of the adrenal glands had no influence on atherogenesis or neointima development. The influence of exogenous glucocorticoids on lesion development was assessed by orally administering dexamethasone (0.1 or 0.8mg/kg/day). Atherosclerotic lesion burden was augmented by dexamethasone administration. Conversely, fibro-proliferative neointimal proliferation was inhibited by dexamethasone. However, this effect was obscured by thrombotic lesion development. It was proposed that this thrombotic effect is attributable to increased plasminogen activator inhibitor-1 (PAI-1), which was tested using PAI-1 deficient mice. Although PAI-1 was found to mediate the systemic pro-thrombotic effect of dexamethasone, it is not required for the enhanced development of thrombotic lesions at the site of intra-luminal injury. These results suggest that physiological levels of endogenous glucocorticoids play a limited role in vascular lesion development. Conversely, although exogenous glucocorticoids inhibit fibro-proliferative intimal hyperplasia, they appear to have significant detrimental influences on lesion development, augmenting atherosclerosis and inducing thrombotic neointimal lesion formation following vascular injury. Further research is therefore required to improve the cardiovascular outcome of patients requiring glucocorticoid therapy and for the use of glucocorticoids as antirestenotic agents.