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RVX-208, an inducer of ApoA-I in humans, is a BET bromodomain antagonist.

ABSTRACT: Increased synthesis of Apolipoprotein A-I (ApoA-I) and HDL is believed to provide a new approach to treating atherosclerosis through the stimulation of reverse cholesterol transport. RVX-208 increases the production of ApoA-I in hepatocytes in vitro, and in vivo in monkeys and humans, which results in increased HDL-C, but the molecular target was not previously reported. Using binding assays and X-ray crystallography, we now show that RVX-208 selectively binds to bromodomains of the BET (Bromodomain and Extra Terminal) family, competing for a site bound by the endogenous ligand, acetylated lysine, and that this accounts for its pharmacological activity. siRNA experiments further suggest that induction of ApoA-I mRNA is mediated by BET family member BRD4. These data indicate that RVX-208 increases ApoA-I production through an epigenetic mechanism and suggests that BET inhibition may be a promising new approach to the treatment of atherosclerosis.

SUBMITTER: McLure KG

PROVIDER: S-EPMC3877016 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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RVX-208, an inducer of ApoA-I in humans, is a BET bromodomain antagonist.

McLure Kevin G KG Gesner Emily M EM Tsujikawa Laura L Kharenko Olesya A OA Attwell Sarah S Campeau Eric E Wasiak Sylwia S Stein Adam A White Andre A Fontano Eric E Suto Robert K RK Wong Norman C W NC Wagner Gregory S GS Hansen Henrik C HC Young Peter R PR

PloS one 20131231 12

Increased synthesis of Apolipoprotein A-I (ApoA-I) and HDL is believed to provide a new approach to treating atherosclerosis through the stimulation of reverse cholesterol transport. RVX-208 increases the production of ApoA-I in hepatocytes in vitro, and in vivo in monkeys and humans, which results in increased HDL-C, but the molecular target was not previously reported. Using binding assays and X-ray crystallography, we now show that RVX-208 selectively binds to bromodomains of the BET (Bromodo ...[more]

PMID: 24391744

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Project description:BackgroundApabetalone (RVX-208) is a bromodomain and extraterminal protein inhibitor (BETi) that in phase II trials reduced the relative risk (RR) of major adverse cardiac events (MACE) in patients with cardiovascular disease (CVD) by 44% and in diabetic CVD patients by 57% on top of statins. A phase III trial, BETonMACE, is currently assessing apabetalone's ability to reduce MACE in statin-treated post-acute coronary syndrome type 2 diabetic CVD patients with low high-density lipoprotein C. The leading cause of MACE is atherosclerosis, driven by dysfunctional lipid metabolism and chronic vascular inflammation (VI). In vitro studies have implicated the BET protein BRD4 as an epigenetic driver of inflammation and atherogenesis, suggesting that BETi may be clinically effective in combating VI. Here, we assessed apabetalone's ability to regulate inflammation-driven gene expression and cell adhesion in vitro and investigated the mechanism by which apabetalone suppresses expression. The clinical impact of apabetalone on mediators of VI was assessed with proteomic analysis of phase II CVD patient plasma.ResultsIn vitro, apabetalone prevented inflammatory (TNFα, LPS, or IL-1β) induction of key factors that drive endothelial activation, monocyte recruitment, adhesion, and plaque destabilization. BRD4 abundance on inflammatory and adhesion gene promoters and enhancers was reduced by apabetalone. BRD2-4 degradation by MZ-1 also prevented TNFα-induced transcription of monocyte and endothelial cell adhesion molecules and inflammatory mediators, confirming BET-dependent regulation. Transcriptional regulation by apabetalone translated into a reduction in monocyte adhesion to an endothelial monolayer. In a phase II trial, apabetalone treatment reduced the abundance of multiple VI mediators in the plasma of CVD patients (SOMAscan® 1.3 k). These proteins correlate with CVD risk and include adhesion molecules, cytokines, and metalloproteinases. Ingenuity® Pathway Analysis (IPA®) predicted that apabetalone inhibits pro-atherogenic regulators and pathways and prevents disease states arising from leukocyte recruitment.ConclusionsApabetalone suppressed gene expression of VI mediators in monocytes and endothelial cells by inhibiting BET-dependent transcription induced by multiple inflammatory stimuli. In CVD patients, apabetalone treatment reduced circulating levels of VI mediators, an outcome conducive with atherosclerotic plaque stabilization and MACE reduction. Inhibition of inflammatory and adhesion molecule gene expression by apabetalone is predicted to contribute to MACE reduction in the phase III BETonMACE trial.

Project description:Bromodomains have emerged as attractive candidates for the development of inhibitors targeting gene transcription. Inhibitors of the bromo-and-extra-terminal (BET) family recently showed promising activity in diverse disease models. However, the pleiotropic nature of BET proteins regulating tissue specific transcription has raised safety concerns and suggested that attempts should be made for domain-specific targeting. Here we report that RVX-208, a compound currently in phase II clinical trials, is a BET bromodomain inhibitor specific for second bromodomains (BD2). Co-crystal structures revealed binding modes of RVX-208 and its synthetic precursor and fluorescent recovery after photobleaching demonstrated that RVX-208 displaces BET proteins from chromatin. However, gene expression data showed that BD2 inhibition only modestly affects BET-dependent gene transcription. Our data demonstrate the feasibility of specific targeting within the BET family resulting in different transcriptional outcomes and highlight the importance of BD1 in transcriptional regulation HepG2 Cells were treated with eitther DMSO or 0.5uM JQ1 or 5uM RVX-208. Three samples per condition, total of nine samples. Inhbitor treatment was carried out for 4h before RNA was extracted. HepG2 cells (ATCC: HB-8065) were maintained in M-NM-1-MEM (Cat.#BE12-169F; BioWhittaker) supplemented with 10 % heat-inactivated foetal calf serum (PAA #A15-152), non-essential amino acids (Cat. #M7145; Sigma), glutamine (Cat.#M11-004; PAA), and vitamins (Cat.#M6895; Sigma). Cells were grown at 37 M-BM-0C in a humidified cabinet at 5 % CO2 (Heraeus Function Line). For experiments, cells were seeded the day prior to treatment at 2x105/ml. Treatments were performed for 4 h so that a final concentration of 0.1 % DMSO (Cat.#D1435; Sigma) was achieved. At harvest, cells were washed once with PBS (Cat.#H15-002; PAA), and lysed in situ using RLT buffer supplemented with 10 M-NM-<l/ml M-NM-2-mercaptoethanol (Cat.#M7522; Sigma). Total RNA was extracted and prepared using RNeasy columns (Cat.#74106 plus; Qiagen) including a Qia shredding step (Cat.#79656; Qiagen) and an on-column DNAse digestion (Cat.#EN0521; Fermentas), according to the manufacturerM-bM-^@M-^Ys instructions. The resulting RNA was quantified and quality controlled using a Nanodrop spectrophotometer (model ND1000; Thermo Fisher). RNA integrity was assessed on a BioAnalyzer (model G2938C; Agilent Laboratories, USA) and all samples had a RNA Integrity Number (RIN) M-bM-^IM-% 9. Labelled sense ssDNA for hybridization was generated from 200 ng starting RNA with the Ambion WT expression kit (Cat.#4411973; Ambion) and the Affymetrix GeneChip WT Terminal Labelling and Controls Kit (Cat.#901525; Affymetrix) according to the manufacturerM-bM-^@M-^Ys instructions. The distribution of fragmented sense ssDNA lengths was measured on the BioAnalyser. The fragmented ssDNA was labelled and hybridized for 17 hours at 45 M-BM-0C on the Affymetrix GeneChip Human Gene 1.0 ST Array (Affymetrix). Chips were processed on an Affymetrix GeneChip Fluidics Station 450 and Scanner 3000 and the affymetrix Command Console (v.3.2.4; Affymetrix) was used to generate CEL files.

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RVX-208, an inducer of ApoA-I in humans, is a BET bromodomain antagonist.

Publications

RVX-208, an inducer of ApoA-I in humans, is a BET bromodomain antagonist.

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