[Optimizing efficacy and security of CAR-T cells, and immune monitoring]. / Optimisation de l'efficacité et de la sécurité d'utilisation des lymphocytes CAR-T.

The immune system plays a critical role in the control and eradication of tumors. A better understanding of the anti-tumor immune mechanisms over the last decade has led to the development of immunotherapies, including cellular therapies such as those using CAR-T cells. These therapies have been remarkably effective in hematological malignancies. However, their application to solid tumors requires some optimization. Many efforts are being made in this regard, both to increase the efficacy of CAR-T cells, and to make them more secure. For the former goal, there is a need for the identification of new targets, better activation strategies, or arming T cells in a way that makes them able to overcome intra-tumoral barriers. For the latter goal, dose adjustment, locoregional administration or use of suicide genes are currently investigated as ways to mitigate the risks of this therapy. Together, these adjustments will permit larger applicability of CAR-T cells, in anti-tumor immunity, but also in the context of auto-immune diseases or fibrolytic therapies.

Title: Optimisation de l'efficacité et de la sécurité d'utilisation des lymphocytes CAR-T. Abstract: Le système immunitaire joue un rôle déterminant dans le contrôle et l'éradication des tumeurs. Une meilleure compréhension des mécanismes en jeu a permis le développement des immunothérapies, et notamment des thérapies par lymphocytes CAR-T. Ces thérapies ont montré une grande efficacité dans les maladies hématologiques, mais leur application aux tumeurs solides nécessite des optimisations pour améliorer leur efficacité et leur sécurité. Ces ajustements permettront une plus grande applicabilité des lymphocytes CAR-T, non seulement pour les traitements anti-tumoraux mais aussi pour le traitement de maladies auto-immunes ou fibreuses.

Repeated peripheral infusions of anti-EGFRvIII CAR T cells in combination with pembrolizumab show no efficacy in glioblastoma: a phase 1 trial.

We previously showed that chimeric antigen receptor (CAR) T-cell therapy targeting epidermal growth factor receptor variant III (EGFRvIII) produces upregulation of programmed death-ligand 1 (PD-L1) in the tumor microenvironment (TME). Here we conducted a phase 1 trial (NCT03726515) of CAR T-EGFRvIII cells administered concomitantly with the anti-PD1 (aPD1) monoclonal antibody pembrolizumab in patients with newly diagnosed, EGFRvIII+ glioblastoma (GBM) (n = 7). The primary outcome was safety, and no dose-limiting toxicity was observed. Secondary outcomes included median progression-free survival (5.2 months; 90% confidence interval (CI), 2.9-6.0 months) and median overall survival (11.8 months; 90% CI, 9.2-14.2 months). In exploratory analyses, comparison of the TME in tumors harvested before versus after CAR + aPD1 administration demonstrated substantial evolution of the infiltrating myeloid and T cells, with more exhausted, regulatory, and interferon (IFN)-stimulated T cells at relapse. Our study suggests that the combination of CAR T cells and PD-1 inhibition in GBM is safe and biologically active but, given the lack of efficacy, also indicates a need to consider alternative strategies.

Interferon Alpha Therapy Increases Pro-Thrombotic Biomarkers in Patients with Myeloproliferative Neoplasms.

Myeloproliferative neoplasms (MPN) are associated with an increased risk of arterial and venous thrombosis. Pegylated-interferon alpha (IFN) and hydroxyurea (HU) are commonly used to treat MPN, but their effect on hemostasis has not yet been studied. The aim of our study was to determine whether IFN and HU impact the biological hemostatic profile of MPN patients by studying markers of endothelial, platelet, and coagulation activation. A total of 85 patients (50 polycythemia vera and 35 essential thrombocythemia) were included: 28 treated with IFN, 35 with HU, and 22 with no cytoreductive drug (non-treated, NT). Von Willebrand factor, shear-induced platelet aggregation, factor VIII coagulant activity (FVIII:C), fibrinogen, and thrombin generation with and without exogenous thrombomodulin were significantly higher in IFN-treated patients compared to NT patients, while protein S anticoagulant activity was lower. In 10 patients in whom IFN therapy was discontinued, these hemostatic biomarkers returned to the values observed in NT patients, strongly suggesting an impact of IFN therapy on endothelial and coagulation activation. Overall, our study shows that treatment with IFN is associated with significant and reversible effects on the biological hemostatic profile of MPN patients. Whether they could be associated with an increased thrombotic risk remains to be determined in further randomized clinical studies.

Hemostatic disorders in a JAK2V617F-driven mouse model of myeloproliferative neoplasm.

Thrombosis is common in patients suffering from myeloproliferative neoplasm (MPN), whereas bleeding is less frequent. JAK2(V617F), the main mutation involved in MPN, is considered as a risk factor for thrombosis, although the direct link between the mutation and hemostatic disorders is not strictly established. We investigated this question using conditional JAK2(V617F) knock-in mice with constitutive and inducible expression of JAK2(V617F) in hematopoietic cells, which develop a polycythemia vera (PV)-like disorder evolving into myelofibrosis. In vitro, thrombosis was markedly impaired with an 80% decrease in platelet-covered surface, when JAK2(V617F) blood was perfused at arterial shear over collagen. JAK2(V617F) platelets presented only a moderate glycoprotein (GP) VI deficiency not responsible for the defective platelet accumulation. In contrast, a decreased proportion of high-molecular-weight von Willebrand factor multimers could reduce platelet adhesion. Accordingly, the tail bleeding time was prolonged. In the FeCl3-induced thrombosis model, platelet aggregates formed rapidly but were highly unstable. Interestingly, vessels were considerably dilated. Thus, mice developing PV secondary to constitutive JAK2(V617F) expression exhibit a bleeding tendency combined with the accelerated formation of unstable clots, reminiscent of observations made in patients. Hemostatic defects were not concomitant with the induction of JAK2(V617F) expression, suggesting they were not directly caused by the mutation but were rather the consequence of perturbations in blood and vessel homeostasis.