Vildagliptin acts primarily by inhibiting DPP-4, an enzyme responsible for the degradation of the incretin hormones GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). Inhibition of DPP-4 activity by vildagliptin results in a rapid and complete increase in endogenous levels of the incretin hormones GLP-1 and GIP after meals and fasting.