[allmendream]

Yet the active domains of their proteins (coded for by their DNA) are surprisingly well conserved between species.

Thus a molecule that binds to the XYZ receptor in mice is very likely to bind to the XYZ receptor in rats and dogs and humans - be metabolized by the same enzymes into the same products, etc.

And all of this is checked before the therapeutic goes into humans. Does it bind to the human version of the target? Do the metabolites produced in model species correspond to those that would be produced in humans (using human liver cells), etc.

People wonder why monkeys are used in drug trials - because they are much more likely to be a relevant model.

But it is amazing that there is so much similarity in the active working parts of proteins between mice and humans that they are useful at all!

[FredZarguna]

Yes, all true, and it is quite remarkable that you can do meaningful research on mice. But, unfortunately a lot of this ultimately comes down to the divergent behavior of one specific receptor or one specific protein. [And luckily! Otherwise, just for example, viruses would be able to cross species barriers much more easily.]