Few drugs in recent history have made as big a splash as GLP-1–based therapies.
First developed for type 2 diabetes, these drugs became remarkably effective treatments for obesity and have since earned FDA approval for cardiovascular disease, chronic kidney disease, obstructive sleep apnea, and metabolic liver disease. Exciting as these approvals are, it is not especially surprising that drugs developed for metabolic disease would also work in conditions with a clear metabolic component.
More surprising is that these drugs are now being investigated for conditions that seem far removed from metabolism. It’s intuitive that a therapy producing weight loss and improved glycemic control might lower cardiovascular risk; that the same therapy is being studied for substance use disorder is genuinely puzzling. And yet, we are constantly encountering claims that GLP-1–based therapies might treat everything from cancer to traumatic brain injury.
Follow the headlines and it’s easy to conclude that GLP-1–based drugs can do almost anything. But as the list of potential indications grows, the mere fact that these drugs appear to work in another disease is becoming less interesting than the question of why they work. How much reflects a genuinely distinct biological effect, and how much is simply the same metabolic benefit appearing in one disease after another?
Clinical trials are not usually designed to answer that question. They can show that a drug reduced cardiovascular events, for example, without telling us whether the benefit came from weight loss, lower central adiposity, improved glycemic control, reduced inflammation, a direct vascular effect, or some combination of these pathways.
Still, the details can offer clues: who was enrolled, how quickly the benefit appeared, whether greater weight loss produced greater improvement, and whether comparable metabolic changes achieved in other ways led to similar outcomes.
