Setmelanotide is a selective MC4 receptor agonist licensed for 6 years and older with obesity due to pro-opiomelanocortin deficiency, proprotein subtilisin/kexin type 1 (PCSK1) deficiency, and leptin receptor (LEPR) deficiency confirmed by genetic testing and is currently being trialled in other rare genetic disorders associated with obesity including Bardet-Biedl Syndrome and Alström Syndrome (138, 139). The gene discussed is PCSK1; the disease is Bardet-Biedl syndrome.