In early phase 2 clinical trials, treatment with cotadutide versus a mono GLP-1 receptor agonist (liraglutide) in patients with type 2 diabetes mellitus (T2DM) and obesity led to clinically relevant reductions in blood glucose, body weight and liver fat, and improvements in liver health markers, including serum transaminases and N-terminal type III collagen pro-peptide compared with GLP-1 receptor agonism alone4,6–8. The gene discussed is GLP1R; the disease is obesity due to melanocortin 4 receptor deficiency.