SPA70 is an orally available, selective, competitive antagonist of the human pregnane X receptor (hPXR) (IC50=540 nM), which blocks the hPXR nuclear receptor signaling pathway and its mediated transcriptional activation of drug metabolizing enzymes (e.g., CYP3A4, MDR1) . SPA70 exhibits low toxicity in both in vitro and in vivo models and can be used to study hPXR-mediated cancer drug resistance and liver injury[1][2][3].