Sitagliptin, known chemically as 4-(((S)-1-((2S,4R)-4-Hydroxy-2-((4-(4-methylthiazol-5-yl)benzyl)carbamoyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)amino)-4-oxobutanoic acid, is used in pharmaceutical research as a selective DPP-4 (dipeptidyl peptidase-4) protease inhibitor. It is particularly investigated for its potential in treating metabolic disorders and type 2 diabetes due to its ability to modulate enzyme activity involved in glucose regulation. It functions by mimicking natural peptide substrates, binding selectively to the active site of DPP-4, thereby prolonging incretin hormone activity and influencing insulin signaling pathways. Also explored for use in developing therapies for obesity-related conditions owing to its stability and specificity in biological systems.