Bear -

Did you post this one already?

I didn't see it on the first couple screens of the link library,

but admit I didn't do a thorough search.  

Below are just the abstract and the discussion section - whole article at the link.

RVX-297, a BET Bromodomain Inhibitor, Has Therapeutic Effects in Preclinical Models of Acute Inflammation and Autoimmune Disease

http://molpharm.aspetjournals.org/content/92/6/694

Abstract

Bromodomain (BD) and extra-terminal domain containing proteins (BET) are chromatin adapters that bind acetylated histone marks via two tandem BDs, BD1 and BD2, to regulate gene transcription. BET proteins are involved in transcriptional reprogramming in response to inflammatory stimuli. BET BD inhibitors (BETis) that are nonselective for BD1 or BD2 have recognized anti-inflammatory properties in vitro and counter pathology in models of inflammation or autoimmune disease. Although both BD1 and BD2 bind acetylated histone residues, they may independently regulate the expression of BET-sensitive genes. Here we characterized the ability of RVX-297, a novel orally active BETi with selectivity for BD2, to modulate inflammatory processes in vitro, in vivo, and ex vivo. RVX-297 suppressed inflammatory gene expression in multiple immune cell types in culture. Mechanistically, RVX-297 displaced BET proteins from the promoters of sensitive genes and disrupted recruitment of active RNA polymerase II, a property shared with pan-BETis that nonselectively bind BET BDs. In the lipopolysaccharide model of inflammation, RVX-297 reduced proinflammatory mediators assessed in splenic gene expression and serum proteins. RVX-297 also countered pathology in three rodent models of polyarthritis: rat and mouse collagen-induced arthritis, and mouse collagen antibody–induced arthritis. Further, RVX-297 prevented murine experimental autoimmune encephalomyelitis (a model of human multiple sclerosis) disease development when administered prophylactically and reduced hallmarks of pathology when administered therapeutically. We show for the first time that a BD2-selective BETi maintains anti-inflammatory properties and is effective in preclinical models of acute inflammation and autoimmunity.

Discussion 

Small-molecule pan-BETis have been useful in delineating roles for BET BDs in inflammatory processes and autoimmune disorders (Nicodeme et al., 2010; Barrett et al., 2014; Zhang et al., 2015; Chen et al., 2016). Whereas most BETis in development have similar affinity for both (i.e., pan) BET protein BDs, RVX-297 is a novel, orally bioavailable BETi with selectivity for BD2 (Kharenko et al., 2016). Apabetalone is another BD2-selective BETi currently in clinical trials for cardiovascular disease (McLure et al., 2013); the anti-inflammatory properties of apabetalone have been demonstrated in a mouse model of atherosclerosis (Jahagirdar et al., 2014). To extend the understanding of the anti-inflammatory properties of RVX-297, we examined the activity of RVX-297 in vitro and in five preclinical in vivo models of autoimmune pathology including, the mouse LPS, rCIA, mCIA, mCAIA, and mouse EAE models. RVX-297 reduced the response to inflammatory stimuli in macrophages, B cells, T cells, and fibroblasts, which is consistent with the displacement of BET proteins from chromatin. In vivo, RVX-297 drastically reduced disease symptoms in rodent models of endotoxemia and autoimmune disease. In addition, RVX-297 regulated inflammatory gene expression in disease-contributing cell types.

Responses to inflammatory stimuli are complex. The activation of inflammatory gene expression involves epigenetic restructuring of chromatin and the associated regulatory elements to alter the transcriptome (Brown et al., 2014). Current evidence suggests that anti-inflammatory properties of BETi are mediated through the displacement of BET proteins from acetylation marks on chromatin, disrupting the assembly of transcriptional machinery and the subsequent expression of BET sensitive genes (Nicodeme et al., 2010). BETis also effectively suppress inflammatory responses mediated by nuclear factor-κ-light-chain-enhancer of activated B cells (NF-κB) (Brown et al., 2014), a proinflammatory transcription factor and master regulator of inflammatory and immune responses (for review, see Baltimore, 2011; Smale, 2011). For example, the NF-κB pathway is activated by LPS, and the pan-BETi I-BET762 has been shown to prevent or diminish the incidence of death in mice given lethal doses of LPS (Nicodeme et al., 2010). These data indicate that the modulation of BET protein activity can attenuate the cytokine storm associated with endotoxemic shock or sepsis. Genetic and chemical approaches have demonstrated the critical role of BRD2 and BRD4 in the regulation of inflammatory cytokine expression in macrophages (Belkina et al., 2013). In our study, RVX-297 blunts LPS-induced endotoxemia in mice, resulting in reduced numbers of serum cytokines, inflammatory markers (Fig. 3A; Supplemental Table 1), and LPS-induced splenic gene expression of IL-6 and IL-17 (Fig. 3B). Our results are consistent with studies linking BETi with the suppression of exaggerated inflammatory responses tied to cytokine production and NF-κB activation (Huang et al., 2009; Belkina et al., 2013).

Because RVX-297 mediated the suppression of key factors that drive autoimmune disease in LPS-treated mice, studies were extended to preclinical autoimmune models. Rodent models of RA provide insights into the perpetuation and treatment of pathogenic joint inflammation. The CIA and CAIA models are characterized by hallmarks of arthritis, including measurable polyarticular inflammation, marked cartilage destruction in association with pannus formation, and mild to moderate bone resorption and periosteal bone proliferation (Bendele, 2001; Williams, 2004). In three arthritis models, disease indices were dramatically reduced in RVX-297–treated animals, resulting in the maintenance of joint structure and integrity, likely arising from decreased production of cytokines and inflammatory mediators. The pan-BETi JQ1 is also efficacious in the mCIA model, stressing a role for BET proteins in the inflammatory response, the production of autoantibodies, and joint damage arising in this model (Zhang et al., 2015). In addition, a fundamental role for IL-17 in the CAIA model disease development has been demonstrated (Plum et al., 2009). The ability of RVX-297 to downregulate IL-17 production (Tables 1 and 6; Supplemental Table 1) may contribute to the efficacy of this compound.

TH17 cells are fundamental in promoting human autoimmune disease, which is recapitulated in mouse models (Nakae et al., 2003; Komiyama et al., 2006). T cells of both TH1 and TH17 lineages are involved in generating disease conditions in EAE (Kroenke et al., 2008). Cytokines IL-23, IL-6, and IL-17, which are critical for TH1 and TH17 differentiation and the production of these T cells, play a fundamental and nonredundant role in EAE progression (Thakker et al., 2007). Therefore, pharmacological suppression of these cytokines, or TH17 differentiation, has therapeutic potential in T cell–mediated autoimmune disorders. Further, the neutralization of IL-17 through targeting of the protein or its receptor prevents the development of EAE (Hofstetter et al., 2005). Previous studies have demonstrated that JQ1 ameliorates EAE symptoms and established that BET BDs are critical in the differentiation and function of TH17 cells (Mele et al., 2013). RVX-297 suppressed EAE pathology when administered to mice either prophylactically or therapeutically. In addition, the production of multiple cytokines in vivo (Fig. 7) and ex vivo (Table 6) was suppressed by RVX-297. In vivo efficacy was comparable or superior to that of the S1P1 agonist FTY720 (fingolimod), an approved therapeutic agent for the treatment of MS. RVX-297 inhibits TH1 and TH17 responses, both of which play pivotal roles in the development and progression of MS and other autoimmune indications. Additional analysis of cytokine production indicates that RVX-297 affects multiple contributors to autoimmune pathology. Importantly, RVX-297 decreased CD4+ cells producing proinflammatory cytokines in the brains and spinal cords of EAE mice (Fig. 8), indicating reduced infiltration of T cells into the CNS. These results underscore the effects of BETi in the periphery to alleviate the effects in the CNS (Tzartos et al., 2008). Although RVX-297 was effective in reducing IL-17–producing T cells in the CNS, more profound effects were reported with JQ1 (Mele et al., 2013). This variance may be due to differences in compound affinities for BET BDs. Results from this study and from other laboratories have shown that BET BD inhibition protects mice from autoimmunity (Belkina et al., 2013; Mele et al., 2013; Zhang et al., 2015). Therefore, BETi holds promise for the treatment of autoimmunity, even after disease symptoms have been established.

A variety of pharmacological therapies has been approved for the treatment of autoimmune disorders. Antibodies that capture or neutralize key cytokines to promote immunosuppression are prevalent (for review, see Chan and Carter, 2010). Because autoimmunity causing host tissue damage and antimicrobial immunity involves the same processes, infection is a concern due to the immunosuppressive nature of these drugs (for review, see Caspi, 2008). Therefore immunosuppressive therapies are often not well suited for long-term treatment. Of note, the BD2-selective compound apabetalone had no effect on the incidence of infestations or infections in a 6-month clinical trial of patients with cardiovascular disease (Nikolic et al., 2015; Nicholls et al., 2016). This outcome may be a result of suppressing inflammatory processes to levels that do not entirely impair immune function, thereby avoiding the risk of infection.

In contrast to targeting single entities in inflammatory or autoimmune pathways, BETi simultaneously downregulates multiple inflammatory processes. Concurrent targeting of contributors to inflammation from a variety of immune cell types sets BETi apart from current therapies that act on a single inflammatory component or process. Studies indicate that BET protein BDs function cooperatively (Schroder et al., 2012). How BD1 is impacted, directly or indirectly, by BD2-selective inhibition requires further investigation. Our results suggest that BD2-selective BET inhibitors are sufficient to ameliorate autoimmune pathology and may dampen detrimental immune responses without adversely compromising immune function. Future studies will be required to determine whether RVX-297 BETi is clinically effective in autoimmune conditions.