SRT1720 is a selective activator of human SIRT1 (0.16 µM and 781%) versus the closest sirtuin homologues, SIRT2 and SIRT3. It binds to the SIRT1 enzyme-peptide substrate complex at an allosteric site amino-terminal to the catalytic domain and lower the Michaelis constant for acetylated substrates. In animal studies SRT1720 was found to improve insulin sensitivity and lower plasma glucose levels in fat, muscle and liver tissue, and increased mitochondrial and metabolic function. The claim that SRT1720 is a SIRT1 activator has been questioned and further defended since 2007.