Discovery of YA8026, an optimized human constitutive androstane receptor activator from a novel ML241-derived scaffold

Abstract

The human constitutive androstane receptor (hCAR) regulates drug metabolism and represents a promising target for enhancing cyclophosphamide (CPA) bioactivation through CYP2B6 induction. However, currently available hCAR activators are mostly derived from the CITCO scaffold and often exhibit suboptimal physicochemical properties. Here, we report the discovery of a structurally distinct class of hCAR activators based on the 2,4-diaminopyrimidine scaffold of ML241, a known p97 ATPase inhibitor identified through high-throughput screening (HTS). Systematic structure-activity relationship (SAR) studies enabled optimization of this scaffold and led to the identification of 43 (YA8026) as a potent and selective hCAR activator. YA8026 demonstrated sub-micromolar potency, favorable selectivity over human pregnane X receptor (hPXR) and other nuclear receptors, and robust functional activity in human primary hepatocytes, including selective CYP2B6 induction and hCAR nuclear translocation. Notably, these compounds no longer retained p97 inhibitory activity, highlighting successful scaffold repurposing. In addition, YA8026 exhibited minimal kinase inhibition across a panel of 280 kinases, favorable chemical and plasma stability, and low cellular toxicity. Together, this work establishes a new non-CITCO chemotype for hCAR activation and identifies YA8026 as a promising lead compound for further development.