How Might Bromodomain and Extra-Terminal (BET) Inhibitors Operate in Cardiovascular Disease?

Abstract

Bromodomain and extra-terminal (BET) inhibitors, acting via epigenetic mechanisms, have been developed recently as potential new treatments for cancer, including prostate cancer, and inflammatory conditions. Some BET inhibitors, such as RVX-208, also raise high-density lipoprotein cholesterol (HDL-C) and apolipoprotein A-1 levels. A recent meta-analysis of three small trials (n = 798) found that RVX-208 protected against major adverse cardiovascular events (MACE), raising the question as to whether this protective effect was an artefact, a chance finding, or mediated by HDL-C, anti-inflammatory pathways, or other factors. Notably, the effect of RVX-208 on MACE was largely driven by revascularizations, but fewer interventions in the treatment arm could have arisen accidently from favorable effects of RVX-208 on HDL-C and C-reactive protein influencing decisions about patient care. A larger (n = 2400) trial of RVX-208, BETonMACE (NCT02586155), with a more restricted definition of MACE, excluding hospitalizations, will shortly provide clarity. A successful BETonMACE trial would raise the question as to whether RVX-208 operates via lipids, inflammation, or other means, because several previous HDL-C modulators and anti-inflammatories have not provided effective means of treating cardiovascular disease and reducing overall mortality. Re-conceptualizing cardiovascular disease within the well-established evolutionary biology theory that growth and specifically reproduction trade-off against longevity might provide a more comprehensive explanation. Drivers of the gonadotropic axis, particularly androgens, suppress both HDL-C and the immune system while promoting ischemic heart disease and stroke. As such, any effects of RVX-208 on cardiovascular disease might be the result of reducing androgens, of which higher HDL-C and reduced inflammation are biomarkers. Notably, several other effective treatments for cardiovascular disease, such as statins and spironolactone, are known anti-androgens. Results of the BETonMACE trial, and corresponding insight about the mechanism of BET inhibitors in cardiovascular disease, are eagerly awaited.