I think it is only approved for treatment in Japan
But it has been around for at least 20 years. The safety profile is extremely well known.
I don't even want to know what role lobbyists play in selecting the drugs used for the trial.
Clearly if they played a big role they did a terrible job with how many of these drugs are off patent.
Probably not a lot. Most of these are out of patent.
I guarantee you that Gilead has at least considered filing a patent application on a new use of the old compound. And they will probably get a grant. Same for all the other treatments.