Background: T-cells engineered to express a chimeric antigen receptor (CAR-T-cells) are a promising cancer immunotherapy. Such targeted therapies have shown long-term relapse survival in patients with B cell leukemia and lymphoma. However, cytokine release syndrome (CRS) represents a serious, potentially life-threatening, side effect often associated with CAR-T cells therapy. The Janus kinase (JAK) tyrosine kinase family is pivotal for the downstream signaling of inflammatory cytokines, including interleukins (ILs), interferons (IFNs), and multiple growth factors. CRS manifests as a rapid (hyper)immune reaction driven by excessive inflammatory cytokine release, including IFN-g and IL-6. Itacitinib is a potent, selective JAK1 inhibitor which is being clinically evaluated in several inflammatory diseases.

Aims: To evaluate in vitro and in vivo the potential of itacitinib to modulate CRS without impairing CAR-T cell anti-tumor activity.

Materials and Methods:In vitro proliferation and cytotoxic activity of T cells and CAR-T cells was measured in the presence of increasing concentrations of itacitinib or tocilizumab (anti-IL-6R). To evaluate itacitinib effects in vivo, we conducted experiments involving adoptive transfer of human CD19-CAR-T-cells in immunodeficient animals (NSG) bearing CD19 expressing NAMALWA human lymphoma cells. The effect of itacitinib on cytokine production was studied on CD19-CAR-T-cells expanded in the presence of itacitinib or tocilizumab. Finally, to study whether itacitinib was able to reduce CRS symptoms in an in vivo setting, naïve mice were stimulated with Concanavalin-A (ConA), a potent T-cell mitogen capable of inducing broad inflammatory cytokine releases and proliferation.

Results:In vitro, itacitinib at IC50 relevant concentrations did not significantly inhibit proliferation or anti-tumor killing capacity of human CAR-T-cells. Itacitinib and tocilizumab (anti-IL-6R) demonstrated a similar effect on CAR T-cell cytotoxic activity profile. In vivo, CD19-CAR-T-cells adoptively transferred into CD19+ tumor bearing immunodeficient animals were unaffected by oral itacitinib treatment. In an in vitro model, itacitinib was more effective than tocilizumab in reducing CRS-related cytokines produced by CD19-CAR-T-cells. Furthermore, in the in vivo immune hyperactivity (ConA) model, itacitinib reduced serum levels of CRS-related cytokines in a dose-dependent manner.

Conclusion: Itacitinib at IC50 and clinically relevant concentrations did not adversely impair the in vitro or in vivo anti-tumor activity of CAR-T cells. Using CAR-T and T cell in vitro and in vivo systems, we demonstrate that itacitinib significantly reduces CRS-associated cytokines in a dose dependent manner. Together, the data suggest that itacitinib may have potential as a prophylactic agent for the prevention of CAR-T cell induced CRS.


Huarte:Incyte corporation: Employment, Equity Ownership. Parker:Incyte corporation: Employment, Equity Ownership. Huang:Incyte corporation: Employment, Equity Ownership. Milone:Novartis: Patents & Royalties: patents related to tisagenlecleucel (CTL019) and CART-BCMA; Novartis: Research Funding. Smith:Incyte corporation: Employment, Equity Ownership.

Author notes


Asterisk with author names denotes non-ASH members.