I previously worked in the United States on Huntington's, for which a system exists. Let us say that we are successful in finding new drugs that are effective in the model system, be it with a fly, a worm or a mouse. We then move on to clinical trials. There is a system in place for Huntington's disease, but there is still nothing for ALS.
In fact, the present problem is that, even if I discover something that works very well with another model, what am I going to do if I do not have the money to carry out a test on a mouse? Clinical trials are assuredly too costly. I cannot pay for everything.