Pre-clinical assessment of JAK inhibitors to ameliorate cytokine storms in Down syndrome

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ABSTRACT. This application is being submitted to PA-18-591 in accordance with NOT-AI-20-031. The recent emergence of SARS-CoV-2 and COVID-19 has created an urgent need for rapid deployment of therapeutic strategies to combat the current pandemic, and major efforts are underway to develop new vaccines and antiviral medications, however, results from these efforts are not expected in the near term. A more immediate approach is to repurpose existing therapeutics approved by the FDA for other conditions to remediate symptoms associated with the most severe COVID-19 outcomes, potentially saving lives and reducing the burden on the healthcare system. Within this framework, cytokine release syndrome (CRS) also known as cytokine storm or hypercytokinemia, has been implicated in acute respiratory distress syndrome, heart failure, and death in patients with COVID-19 (1-5). However, although diverse immune-suppressive strategies to attenuate the cytokine storm are being tested in clinical trials for COVID-19, there is a dearth of pre-clinical data supporting their use to attenuate cytokine-driven pathology. Therefore, we propose here to test the ability of FDA-approved inhibitors of Janus Kinases (JAKs) to mitigate rampant cytokine production and multi-organ inflammation in a mouse model of non-infectious lethal immune hypersensitivity. This mouse model has arisen directly from our work over the past five years that revealed a major role for immune dysregulation in Down syndrome (DS). We demonstrated that individuals with Trisomy 21 (T21), the molecular cause of DS, exhibit constitutively active interferon (IFN) signaling driven by presence of four of the six IFN receptors (IFNRs), located in a single locus on chromosome 21 (chr21) (6). Follow-up studies have revealed 1) signs of IFN activation and chronic inflammation, including numerous cytokines related to CRS, in the plasma proteome of people with T21 (7, 8) and 2) widespread immune dysregulation and IFN hypersensitivity in the blood of people with DS (9, 10). As part of our ongoing work to understand the role of interferon dysregulation in Down syndrome (DS), we recently discovered that the Dp16 mouse model of DS is lethally hypersensitive to chronic innate immune stimulation with the TLR3 agonist polyinosinic: polycytidylic acid [P(I:C)]. Unpublished preliminary data in this proposal include: · P(I:C) treatment of Dp16 mice triggers release of cytokines, including several recently linked to poor prognosis in COVID-19, such as MCP-1, MIP-1α, and IP-10. · The lethal immune hypersensitivity in this model is associated with multi-organ inflammation and liver damage in particular. · The lethality, cytokine release, and inflammation induced by P(I:C) can all be blocked with the JAK1- specific inhibitor INCB054707. We hypothesize that JAK inhibitors are a therapeutically viable strategy to ameliorate COVID-19 associated cytokine release syndrome and associated morbidities. As such, our proposal is responsive to NOT-AI-20-031, particularly as a project “developing medical countermeasures and suitable animal models for pre-clinical testing of vaccines and therapeutics against SARS-CoV-2/COVID-19”. Furthermore, and in keeping with the spirit of the parent award, our data indicate that individuals with DS are likely to be a high-risk group that may experience more severe COVID-19 symptoms and associated cytokine storms in response to SARS-CoV- 2 infection. For this administrative supplement, our specific aim is: 1. To define the ability of all four FDA-approved JAK inhibitors to block lethality and associated cytokine storms in a mouse model of immune hypersensitivity. Encouraged by our preliminary results with the JAK1-specific inhibitor INCB054707, we propose here to test the ability of additional JAK inhibitors to rescue the hyperinflammatory phenotype in the Dp16 mouse model of Down syndrome. We will compare the four FDA-approved JAK inhibitors: baricitinib, ruxolitinib, tofacitinib, and upadacitinib, which have differing specificities for JAK1, JAK2, JAK3, and the related kinase TYK2, as well as varying pharmacodynamic and biodistribution properties. We will define the efficacy of each inhibitor and the therapeutic window in which inhibition of immune stimulation can be achieved. In addition, we will characterize hyperinflammation in key organs and tissues (e.g. lung, heart, liver) at the histological and molecular level to define how these organs respond to JAK inhibition. Importantly, our model system and study design allow for the assessment of inflammation in various tissues, many of which are linked to poor prognosis in individuals with COVID-19 (11-16). Completion of this aim will provide a considerable amount of pre-clinical data in support of ongoing clinical trials aimed at treating deleterious immune responses and serve to bolster the selection of agents available as COVID-19 therapeutics in the near term.