There are several stages of research. For a sufficiently serious condition, it can make sense to take drugs that are only validated at a pre-clinical stage. An

There are several stages of research. For a sufficiently serious condition, it can make sense to take drugs that are only validated at a pre-clinical stage. And there are many conclusions of finished research. A common conclusion is "cures problem A, but may cause problem B", and depending on A and B, those drugs can fail approval. But individuals may place different values on A and B.