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Hemophilia A is a rare hemorrhagic disease due to a lack of functional pro-coagulant factor VIII (FVIII). Severe hemophilia A causes spontaneous bleeding and can even lead to death. The prevention and treatment of hemorrhages is achieved by injection of therapeutic FVIII. This treatment is however complicated by its exorbitant cost and the short half-life of FVIII, hampering the patients’ quality of life. Moreover, in 25 to 35% of the patients, the infusion of exogenous FVIII induces the development of anti-FVIII antibodies which inhibit its pro-coagulant activity and are called “FVIII inhibitors”. During my PhD, I first validated in vivo a new therapeutic strategy, alternative to the actual replacement therapy, using a FVIII-encoding mRNA (Article 1). In the second part, I assessed the possibility to inhibit the anti-FVIII immune response by inhibition of B lymphocytes. To do so, I used an inhibitor of Bruton’s tyrosine kinase (Btk), a kinase involved in the signalling pathway of the receptor of B cells (BCR)(Article 2). Finally, I characterized an hemophilia A mouse model, humanized for MHC. This model lacks FVIII as well as mouse MHC class I and II expression and is transgenic for human MHC I and II. The results obtained during my PhD validate the use of in vitro transcribed mRNA technology for hemophilia A treatment. They also provide a new strategy to inhibit the memory immune response against FVIII and describe a novel mouse model for studying anti-FVIII immune responses.; L’hémophilie A est une maladie hémorragique rare liée à une absence de facteur VIII (FVIII) fonctionnel de la coagulation. Les formes les plus sévères engendrent l’apparition d’hémorragies spontanées, pouvant mettre en jeu le pronostic vital. La prévention et le traitement des saignements se fait par injection de FVIII thérapeutique. Ce FVIII recombinant est difficile à produire, sa demi-vie est courte et la fréquence des injections impacte la qualité de vie des patients. De plus, chez 25 à 35% d’entre eux, l’injection de FVIII exogène provoque l’apparition d’anticorps anti-FVIII qui neutralisent son activité pro-coagulante et sont donc appelés « inhibiteurs ». Au cours de ma thèse, j’ai tout d’abord validé in vivo une nouvelle stratégie thérapeutique, alternative à la thérapie de substitution et qui repose sur l’injection d’ARNm codant le FVIII (Article 1). Dans le deuxième volet, j’ai étudié la possibilité de prévenir la réponse immunitaire anti-FVIII par inhibition des lymphocytes B. Pour cela, j’ai utilisé un inhibiteur de la Btk, une kinase impliquée dans la voie de signalisation du BCR (Article 2). Enfin, j’ai caractérisé un modèle murin d’hémophilie A humanisé pour le CMH. Ce modèle est déficient en FVIII, en CMH I et II murins et transgénique pour les CMH I et II humains (Article 3). L’ensemble des résultats obtenus pendant ma thèse ouvre la voie à la possibilité d’utiliser une nouvelle technologie (les IVT mRNA) dans le traitement de l’hémophilie A. Mes résultats permettent également d’envisager une nouvelle stratégie pour empêcher l’apparition d’une réponse mémoire anti-FVIII et décrivent un nouveau modèle murin pour l’étude de la réponse immunitaire anti-FVIII.

Chronic lymphocytic leukemia (CLL) is the most common hematologic malignancy in France. Much progress has been made in recent years in understanding the pathophysiology of the disease, the definition of diagnostic criteria (>5 G/L of clonal B-lymphocytes), identification of prognostic criteria, including a better understanding of fragile patients, high risk patients and even more recently by the emergence of new highly effective drugs, doing discuss their place in the wide therapeutic panel we have. The treatment of patients with CLL is indicated in patients with progressive stage A, stage B or stage C. The new drugs currently available include not only the new generation of anti-CD20 monoclonal antibodies, type I (ofatumumab) or type II (obinutuzumab), Bcl-2 inhibitors (GDC-0199/ABT-199) and now the new small molecules available orally, including Bruton tyrosine kinase inhibitor (BTK) and phosphor-inositide 3-kinase (PI3K) inhibitor. The role of the biologist in monitoring a patient treated for CLL is essential, the latter to make the diagnosis of CLL, the search for prognostic factors (Binet stage, lymphocyte doubling time, looking for a 17p deletion or TP53 mutations, study of mutational profile of heavy chain genes of immunoglobulins IGHV) and biological monitoring of the different treatments. We will study in this paper the results obtained with these drugs, insisting today more than ever on the need to set up a clinical and biological complementarity to allow optimal medical management of patients with CLL. The mechanisms of actions are discussed, as well as the response criteria we should use to evaluate the effectiveness of these treatments in clinical practice.