Ah, precisely, the lab is not the human body. The fact that you can kill HIV with X in the lab is meaningless. Bleach does a quite adequate job of that. However, we care about in vivo efficacy, and that's qualitatively a different problem. For every thousand drugs that seem promising in isolation in a petri dish (e.g. killing cancer cells and not damaging human tissue) perhaps only a handful make it to human trials, and then not all of those prove effective (or completely safe).
If every new substance that killed HIV or cancer in the lab made the news then you would not have time to read about anything else, there are more than you could imagine. Substances at the "kills X in the lab" stage are generally only of concern to researchers, because the chances that they'll turn into a "cure" are extremely low.
Buying a lottery ticket isn't news. Winning the lottery is. This sort of thing is the former, not the latter.