Emricasan (IDN 6556; PF 03491390) is a member of a new class of drugs to modulate caspases (cell death proteases) involved in the apoptosis and inflammation pathways. Caspases are a family of cysteine proteases that become activated by apoptotic and pro-inflammatory stimuli. Emricasan (IDN 6556; PF 03491390) is a novel and proprietary small molecule, orally active caspase inhibitor designed to block apoptosis of cells in a variety of organ systems. Emricasan (IDN 6556; PF 03491390) has been evaluated in clinical trials to determine its usefulness as an anti-fibrotic drug to delay the progression of hepatitis and prevent the development of cirrhosis.