UCLA

Adoptive transfer of CD19-specific chimeric antigen receptor (CAR)-T cells has shown remarkable efficacy against B-cell malignancies and received FDA-approval in 2017. However, the applicability of this therapy is still hindered by toxicity such as cytokine release syndrome (CRS). Although CRS can often be managed by administration of immunosuppressants, the diagnosis and treatment of CRS depend on the monitoring of indirect clinical signs such as fever and hypotension and is hampered by the inability to monitor the immune response in patients in real-time. Here, we report a strategy to modulate CRS by engineering self-regulating T cells that are able to prevent immune over-stimulation by secreting self-modulators that inhibit certain cytokine signaling pathways. We first constructed a single-chain variant of the antibody tocilizumab, an anti-interleukin 6 receptor alpha (IL-6Rα) antibody that is FDA-approved for CRS treatment, and evaluated its efficacy as self-modulator. CAR-T cells that constitutively secrete this single-chain antibody, which we termed sToci, show significantly reduced cytokine production levels in vitro while maintaining the effector function of CAR-T cells both in vitro and in vivo. Self-modulators that target additional cytokine signaling pathways—including IL-1, IFN-γ, and TNF-α—have also been constructed and shown to be effective agonists of their target cytokines in vitro. To further evaluate the efficacy of self-modulators in vivo, we established a humanized NSG-SGM3 mouse model that recapitulates symptoms of human CRS. T cells engineered to secrete self-modulator proteins were able to reduce the severity of CRS-associated symptoms and prolong survival, confirming the ability to achieve T-cell self-regulation in vivo. Finally, we explore the possibility of inducibly expressing self-modulators upon detection of high cytokine levels or T-cell activation to minimize potential side effects of self-modulator secretion. We report the identification of IL-6-responsive transcriptional regulation elements and the construction and optimization of IL-6-responsive promoters for use in mammalian cell systems.