I had a friend who worked on a weight loss drug for Roche many years ago, and during a meeting at Roche HQ in Basal he informed the management that Americans will not take this drug. They asked why as it worked well, so he explained that a know side effect is that when you are taking this and eat a high fat meal, you basically WILL crap your pants. The management thought that this would be extra encouragement to stick to the diet part of the plan, so my friend explained that Americans will not completely give up cheeseburgers, and the only two side effects they absolutely will not tolerate is crapping themselves, or having their "appendage" fall off. The drug sold great in the first quarter of release, and barely ever again.
The FDA program that granted that exclusivity sounded like a great idea at the time as strictly run clinical trials are a great way to figure out the low occurrence side effects, and also firmly establish the degree of the drug's effect. Unfortunately, it has been the source of some of the most heinous pricing events in recent times. Drugs are expensive for a lot of reasons (some good, some not...I am no pharma apologist), but one of the main good reasons is that a lot of drugs don't work when you try them in large, massively expensive clinical trials (despite looking really good to that point), so you price those failures and the risk of future failures into the things that do work. When doing a trial on a know effective drug that risk of a failed trial is pretty much reduced to your team's ability to execute the trial, and I'm not aware of a trial of this nature that has failed. Therefore, applying the same "pricing in the risk" to this type of drug is complete BS as the risk of failure is so low, and pretty much only based on your own competence.