BE2012 a Novel, REV-ERB Antagonist That Promotes Regenerative Myogenesis in Vivo with Substantially Improved Pharmacokinetics Relative to SR8278

Pharmacological inhibition of REV-ERBs has emerged as a potential therapeutic strategy for several diseases with unmet medical needs. Indeed, chronic treatment with SR8278, a synthetic REV-ERB antagonist, has mitigated pathology in various preclinical models of human musculoskeletal and neurological diseases, including Duchenne muscular dystrophy, epilepsy, Alzheimer disease, Parkinson disease, and frontotemporal dementia. However, SR8278, the first and most widely used REV-ERB antagonist, has poor pharmacokinetic properties, which limits its utility. The REV-ERBs (α and β) are widely expressed nuclear receptors that function as ligand-dependent transcriptional repressors, and the therapeutic potential for inhibition of these receptors remains unclear because of the lack of adequate pharmacological tools. Here, we report BE2012, a significantly improved REV-ERB antagonist with >22-fold longer half-life than SR8278. In a cell-based reporter assay, BE2012 exhibited greater potency toward REV-ERBα (EC50 = 0.38 μM) and REV-ERBβ (EC50 = 0.57 μM) compared with SR8278. Notably, in primary myoblast differentiation assays, BE2012 outperformed SR8278 in increasing the proportion of MyoG+ cells as well as differentiation and fusion indices. In a cardiotoxin-induced muscle injury model, both BE2012 and SR8278 led to increased myofiber cross-sectional area (22%-34% higher than controls). Lastly, transcriptomic profiling revealed remarkable overlap of differentially expressed genes between the 2 compounds, with oxidative phosphorylation and mitochondrial protein complex emerging as the most significantly enriched pathways for both ligands, which have been shown to accelerate regenerative myogenesis. These results establish BE2012 as a refined REV-ERB antagonist for in vivo applications and a valuable tool for deeper exploration of the therapeutic potential of inhibiting REV-ERB activity. SIGNIFICANCE STATEMENT: This study establishes BE2012 as a novel REV-ERBα/β antagonist with a 22-fold longer half-life and improved potency compared with SR8278, the only available REV-ERB antagonist whose poor bioavailability has limited its utility for in vivo use. In an acute muscle injury model in mice, BE2012 promoted regenerative myogenesis and induced a broad transcriptomic reprogramming that was highly concordant with that of SR8278, suggesting it could serve as a new gold-standard REV-ERB antagonist tool compound in the field.