USP20 and obesity due to melanocortin 4 receptor deficiency: Several studies have utilized chemical blockers to assess the roles of USP in metabolic disorders; e.g., GSK2643953A for USP20 in obesity, ML323 and SJB-043 for USP1 in β-cell damage, ML364 for USP2 in hypothalamic function, and HBX41108 for USP7 in diabetic foot ulcers [50,69,117,179].