2-Hydroxy atorvastatin calcium salt is a major metabolite of the HMG-CoA reductase inhibitor atorvastatin, exhibiting potent inhibitory activity with an IC50 of 8 nM. This compound is widely used in pharmacological research to study statin metabolism, pharmacokinetics, and efficacy in both in vitro enzyme assays and in vivo animal models of hyperlipidemia.