GLP-1 Agonists: Wonder Drugs of the 21st Century?

The first drug in a class known as GLP-1 agonists was approved in 2005 to treat diabetes. GLP-1 drugs subsequently proved their mettle to treat obesity and prevent major cardiovascular events and will likely soon be available to treat sleep apnea as well. Looking ahead, their action on the brain is prompting research to gauge their value in curbing drug, alcohol, and nicotine cravings. But these seemingly miracle drugs are costly, not always covered by insurance, and generally need to be taken forever. How do they work, what else might they do, and how do we ensure they are accessible to those who need them most?