I've asked some stem cell researchers how they plan to find the right dose. They look puzzled. They usually ignore the question in the end. We are absolutely and adamantly convinced that this should be considered for research only. And whether it should be research in people is an open question.
Similar problems exist with gene therapy.
Small molecules, the classic drug substance, is a nice way to affect the body, regulating the effect by altering dose. I must either decide that values are relative, that people can do as they please, or that some values are absolute, that there are some things that no people ought to do. If I refuse to make a choice in this matter of either of those two approaches to values, then I am really deciding that values are not absolute. As an observant Jew, I choose to believe every day. I was not brought up with these beliefs.