It wasn't patented anymore and went into generic production. No labs were interested in paying for the studies and CDC didn't run anything.
The government knew that coronavirus pandemics were a serious danger, and they failed completely to follow up on an inexpensive, effective drug.
Today, they dismiss doctors' efforts to use it as "anecdotal."
What is anecdotal is the performance of CDC/NIH/FDA.
There is no reason to use the drug anecdotally. If I had access to the database I could write the article this afternoon and still have time to cook supper.