For less investigated diseases such as ALS or Parkinson it's about 700 trials without any success.
An excellent article discussing why mice studies are not applicable to humans, at least for ALS, is this one: https://www.nature.com/articles/nrneurol.2015.65
[0] http://jamanetwork.com/journals/jama/article-abstract/203577
Sorry not sure where it is located, but you could Google it.
You have locations like this: https://theconversation.com/of-mice-and-men-why-animal-trial...
It showed that of the most-cited animal studies in prestigious scientific journals, such as Nature and Cell, only 37% were replicated in subsequent human randomised trials and 18% were contradicted in human trials. It is safe to assume that less-cited animal studies in lesser journals would have an even lower strike rate.
Not sure why that is higher, but it is phrased weird.
8% seems good to me, as that is the point of testing... but the point of the article was to avoid the hype of these early tests.