First-in-classTransactivator-Free, Doxycycline-inducible IL-18-engineered CAR-T cells for relapsed/refractory B-cell lymphomas

Abstract

Background: Despite their success treating type B cancers, Chimeric Antigen Receptor (CAR) T cells still showed limited efficacy in certain lymphomas and solid tumors. Reinforcing conventional CAR-T cells to release cytokines can improve their efficacy but also increase safety concerns. Several strategies have been developed to regulate their secretion using minimal promoters that are controlled by chimeric proteins harboring transactivators. However, these chimeric proteins can disrupt the normal physiology of target cells.Methods: Co-transduction with CAR19 and Lent-On-Plus-IL-18 LVs allowed for generating constitutive CAR/Dox-inducible IL-18 CAR-T cells that respond to ultra-low doses of doxycycline (iTRUCK19.18). iTRUCK19.18 were evaluated against an aggressive Burkitt lymphoma model in vitro and in vivo, against primary B-cell tumors and against a CD19-engineered pancreatic tumor model. Patient-derived iTRUCK19.18 cells were also generated.Results: iTRUCK19.18 controlled IL-18 release through a dual mechanism dependent on doxycycline and T cell activation, thereby enhancing the safety profile. IL-18 release increased the activation state/proinflammatory profile of T cells in a doxycycline-dependent manner without altering cellular fitness, which was translated into an increased CAR-T cell antitumor activity against aggressive hematologic and solid tumor models. In a clinically relevant context, we generated patient-derived iTRUCK19.18 cells able to significantly increase elimination of primary B cells tumors under doxycycline. Furthermore, IL-18-releasing iTRUCK19.18 polarized pro-tumoral M2 macrophages towards an antitumoral phenotype (M1), suggesting the ability to modulate the tumor microenvironment.Conclusion: We have generated the first transactivator-free inducible TRUCKs from healthy donors and B-cell neoplasms patients. iTRUCK19-18 exhibit dual safety control mechanisms for IL-18 secretion and improved antitumoral activity against type-B neoplasms. Inducible IL-18 secretion not only enhanced T cell potency but could also change the tumor microenvironment to a more antitumoral state.