Sorry, I do not quite follow. FDA regulates the marketing of drugs, biologics, medical devices, etc. They do not regulate the practice of medicine. Your doctor can prescribe whatever they want “off label”.

So for example, manufacturers cannot market erbitux as a cure for migraine headaches because no sponsor has submitted an application to FDA with compelling evidence that it is safe and effective for that particular indication. However, your doctor can still prescribe it for migraines if they so choose. Whether your insurance will pay for it is a different story.