BI 3231 is a potent and selective hydroxysteroid 17ß-dehydrogenase 13 (HSD17B13) inhibitor, with IC 50 s of 1 and 13 nM for hHSD17B13 and mHSD17B13 , respectively. BI 3231 has the potential for the research of nonalcoholic steatohepatitis (NASH) and other liver diseases.