[xr4ti]

I tend think of compassionate use more in the context of medical devices and biologics (e.g. synthetic antibodies) than small molecule drugs. And to reiterate FDA regulation has more to do with marketing (and prescription/reimbursement) than use.

For example, nutritional supplements are often recommended by doctors and incorporated in their practices, but are marketed as "promoting general health and wellness" and not treating a particular condition. Here you don't need any evidence of efficacy (or even safety), you only need to be able to show a "history of use". Many "structure-function" claims push the envelope (ex promotes liver health), but are still legal and FDA has been pretty consistent and clear about where they draw line.