This is not unsubstantiated. It is proven in vitro, and this came out the other day: http://news.southcn.com/nfplus/gdjktt/content/2020-03/09/con...

I haven’t found the source paper if there is one yet — I can’t read Chinese except with google translate

Drugs shown to be effective in vitro routinely fail to show similar effects in vivo.

Chloroquines have a long history of this in viral studies.

The point is that according to what the official Chinese medical line is, it works in vivo. This is apparently confirmed by Korean experience. I understand the skepticism, but you go to war with the data you have, and the data we have indicates Chloroquine works.

The “data” is anecdotal, not even close to the standards of an effectiveness trial.

That said, it’s an approved drug, so it will be applied and we’ll see how it goes. But don’t spread rumors about its effectiveness, because the truth is, we don’t know.

Bleach or a handgun also work "in vitro".

Relevant XKCD: https://www.xkcd.com/1217/

Chloroquines will be tried since they already pass the "safe" bar.

However, I suspect that if they worked "in vivo", we would have compelling data on that from China already. The fact that we don't have such data suggests that they don't.

We seem to have much better data about the effectiveness of standard anti-virals already.