Inhibition of DPP4 results in around 1-fold increase in plasma level of active GLP-1 (Herman et al., 2006), enough to lower HbA1c by 0.6–0.8% in T2D patients but not enough to cause significant body weight loss, neither in animal models nor in humans (Nauck et al., 2007; Esposito et al., 2015). The gene discussed is DPP4; the disease is type 2 diabetes mellitus.