Henrik C. Hansen

RVX-208: A Small Molecule That Increases Apolipoprotein A-I and High-Density Lipoprotein Cholesterol In Vitro and In Vivo

OBJECTIVES The aim of this study was to determine whether a novel small molecule RVX-208 affects apolipoprotein (apo)A-I and high-density lipoprotein cholesterol (HDL-C) levels in vitro and in vivo. BACKGROUND Increased apoA-I and HDL-C levels are potential therapeutic targets for reducing atherosclerotic disease. METHODS HepG2 cells were treated with 0 to 60 mumol/l RVX-208 followed by assays for apoA-I and HDL-C production. For in vivo studies, African green monkeys (AGMs) received 15 to 60 mg/kg/day RVX-208, and the serum was analyzed for lipoprotein levels, HDL-subparticle distribution, cholesterol efflux, and activity of lipid-modifying enzymes. A phase I clinical trial was conducted in healthy volunteers (given 1 to 20 mg/kg/day of RVX-208) to assess safety, tolerability, and pharmacokinetics. RESULTS The RVX-208 induced apoA-I messenger ribonucleic acid and protein synthesis in HepG2 cells, leading to increased levels of pre-beta-migrating and alpha-lipoprotein particles containing apoA-I (LpA-I) in spent media. Similarly, in AGMs, RVX-208 treatment for 63 days increased serum apoA-I and HDL-C levels (60% and 97%, respectively). In addition, the levels of pre-beta(1)-LpA-I and alpha1-LpA-I HDL-subparticles were increased as well as adenosine triphosphate binding cassette AI, adenosine triphosphate binding cassette G1, and scavenger receptor class B type I-dependent cholesterol efflux. These changes were not mediated by cholesteryl-ester-transfer protein. Treatment of humans for 1 week with oral RVX-208 increased apoA-I, pre-beta-HDL, and HDL functionality. CONCLUSIONS RVX-208 increases apoA-I and HDL-C in vitro and in vivo. In AGMs, RVX-208 raises serum pre-beta(1)-LpA-I and alpha-LpA-I levels and enhances cholesterol efflux. Data in humans point to beneficial features of RVX-208 that might be useful for treating atherosclerosis.

RVX-208, an Inducer of ApoA-I in Humans, Is a BET Bromodomain Antagonist

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.

Abstract 5495: BET bromodomain inhibitors abrogate cell cycle progression and induces apoptosis in Myc-induced mouse lymphoma cells without affecting MYC transcription

Overexpression of one of the three MYC genes is a hallmark of many human cancers. They encode transcription factors that regulate expression of a number of genes critical for tumor development. Conditional transgenic mouse models have shown that Myc inhibition causes tumor regression; Myc is therefore an attractive target for therapy, and effective pharmacological Myc inhibition has been a long-standing goal in cancer research. Recent publication have shown that selective inhibition of BET bromodomain and extra-terminal (BET) domain family of proteins, that bind to acetylated lysines on histones, show promise as potent anti-cancer drugs via down-regulation of the MYC oncogene. Here we confirm that two structurally different BET protein inhibitors (BETi), JQ1 (proto-type) and RVX2135, inhibit the proliferation and induce apoptosis of lymphoma cells arising in Myc-transgenic mice. BETi have been reported to directly inhibit MYC transcription. Surprisingly, in our system BET inhibition had no effect on MYC transcription, despite exhibiting broad transcriptional effects evident from expression profiling. Our data challenge the prevailing view that BETi operate primarily via suppression of MYC transcription in hematological malignancies. Instead we suggest that BET proteins have Myc-independent pleiotropic effects that should be exploited to treat a wide range of cancers. Myc still remains a challenging target for therapy to date. Citation Format: Joydeep Bhadury, Lisa M. Nilsson, Lydia Green, Zhoulei Li, Emily M. Gesner, Somsundar Veppil Muralidharan, Henrik C. Hansen, Ulrich B. Keller, Kevin G. Mclure, Jonas A. Nilsson. BET bromodomain inhibitors abrogate cell cycle progression and induces apoptosis in Myc-induced mouse lymphoma cells without affecting MYC transcription. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5495. doi:10.1158/1538-7445.AM2014-5495