According to the article (and Wikipedia), it's a novel antiviral developed to treat COVID-19, and has reached (or completed, by now?) Phase III trials in Japan,

According to the article (and Wikipedia), it's a novel antiviral developed to treat COVID-19, and has reached (or completed, by now?) Phase III trials in Japan, and is currently in use there under an EUA (although I assume the acronym may be different in Japan). If this works for people who have had smell & taste lost for years after recovery, that would imply that the ongoing symptoms were the result of a lingering infection. I'm not sure the referenced study demonstrates that -- as near as I can tell, it was clinically evaluated in people who had new COVID-19 infections.