GIP and obesity due to melanocortin 4 receptor deficiency: More recently, clinical trials involving drugs that combine GLP-1 receptor agonism with agonism or antagonism of other receptors, such as those for GIP or glucagon, have shown considerable promise in the management of T2D (4) and obesity (5) (eg, the triple GLP-1/GIP/glucagon RA, retatrutide).