Myeloid cell-targeted miR-146a mimic alleviates NF-κB-driven cytokine storm without interfering with CD19-specific CAR T cell activity against B cell lymphoma

Abstract

Background: NF-κB is a key regulator of inflammation, myeloproliferation and cancer progression, with an important role in leukemogenesis. Despite therapeutic potential, targeting NF-κB proved challenging. However, in non-malignant myeloid cells NF-κB activity is tightly regulated through many molecular mechanisms, including miRNA. Methods: Here, we describe an original approach to NF-κB inhibition using miR146a, which targets upstream regulators of NF-κB signaling. We generated a myeloid cell-targeted NF-κB inhibitor by tethering a chemically-modified miR146a mimic oligonucleotide to a scavenger receptor (SR)/Toll-like receptor 9 (TLR9) ligand (C-miR146a). Results: Unlike an unconjugated miR-146a molecule, C-miR146a was rapidly internalized and delivered to cytoplasm of target myeloid cells such as macrophages or myeloid leukemia cells. C-miR146a reduced protein levels of classic miR-146a targets, IRAK1 and TRAF6, thereby efficiently blocking NF-κB activation in target cells. Intravenous injections of C-miR146a mimic to miR-146-deficient mice prevented excessive NF-κB activation in myeloid cells, thereby alleviating myeloproliferation and exaggerated inflammatory responses to bacterial challenge. The NF-κB-driven release of IL-1 and IL-6 from monocytes is known to be responsible for cytokine release syndrome (CRS), which can occur in response to bacterial infections, antibody-based therapies and relatively frequently as a serious adverse effect of chimeric antigen receptor (CAR) T-cell therapies. While low expression of miR146a has not yet been implicated in CRS, C-miR146a treatments did reduce pro-inflammatory activity of human monocytes, at the level of IL-1 and IL-6 production, induced by the CD19-specific but not by the naive CAR T cells in vitro. Repeated systemic administration of C-miR146a oligonucleotide alleviated human monocyte-dependent CRS in xenotransplanted B-cell lymphoma model without impeding the on-target therapeutic effects of CAR T-cells against lymphoma cells. Conclusions: Our results demonstrate potential of using myeloid cell-targeted miR146a mimics for treatment of inflammatory diseases and prevention of potential side effects of immunotherapies. The SR/TLR9-targeted miR-146a mimic design provides an outline for the development of miRNA therapeutics for a variety of myeloid cell-related diseases.