I think the grandparent meant "fundamentalism" as "mechanistic", and lots of things we can know (as you say using the scientific method) to be useful long before we have a good mechanistic explanation of how they work.
Some examples: aspirin (willow bark used for thousands of years, drug synthesized in 1897 and mechanism explained almost 100y later), or general anesthesia used again since mid 1800s and the mechanism is quite still debated.
This is not to downplay all the long term, or developmental, risks that using something novel can result in. But we can empirically know something about the effects without having good mechanistic models.
But it is usually not necessary for approval of a compound to be able to describe how it works on a molecular or cellular level. What you need to show are three things: efficacy, safety and quality, so basically: the compound has the intended clinical benefit, has an acceptable safety profile and can be produced with a consistent manufacturing quality. Most compounds fail because of lack of efficacy (roughly half), and roughly a third because of lack of acceptable safety.
The vast majority of drug candidates don’t make it to the trial stage. Much of the research has to be defensible prior to the trial and what makes them defensible is having a mechanism for action. Of course once a drug is being used off label there starts to be some empirical data which can be used for trials, and it seems that we’ll get lucky with GLP1-As.
You are entirely correct. New compounds for trials do not come out of thin air, you usually derive them from compounds you already know how and why they work. For instance, we know very well how Semaglutide works, same goes for many other peptides that are currently being studied. However, you are correct that we do not understand why they would help for ME/CFS, simply because we do not understand ME/CFS in the first place. As I've written above, it's a severely neglected disease.
Anyway, I don't think we really disagree, I rather misunderstood your original post. It's good to hear that these new peptides are helping with your condition, and I wish you all the best!
Thanks for the feedback, I’m noticing that ‘fundamentalism’ didn’t translate properly and I should have referred to first principles and mechanisms of action. I need better words for these and I will try to find them.
As a fun aside, consider the effect of the birthday paradox on empiricism, as the pool of candidates grows larger the probability of a match increases substantially as potential matching candidates increases quadratically.
Some examples: aspirin (willow bark used for thousands of years, drug synthesized in 1897 and mechanism explained almost 100y later), or general anesthesia used again since mid 1800s and the mechanism is quite still debated.
This is not to downplay all the long term, or developmental, risks that using something novel can result in. But we can empirically know something about the effects without having good mechanistic models.