What do you have in mind specifically? I can think of some mild issues that are similar for any behaviour-affecting drugs, but it sounds like there's more?
It in no way is a “downer”, and is often given semi-offlabel interchangeably with standard SSRIs for depression. Also the article quotes $3/pill but is widely available as generic for < $.10/pill.
If this deeply studied—in humans—and readily accessible drug provides an option for those who seek treatment, wonderful.
Hence, it needs to be actually phase 2 trialled properly for this indication.
If the indication requires a genetic test beforehand, that's a minor ethical problem right there, in terms of privacy.
Well, then you don't want to take it. But there's not an ethical issue there unless you're forced to take it.
If you're so autistic that you're essentially nonfunctional, and someone decides for you, do you see that as an ethical issue?