Even if it had shrunk it by 50% for one person, treatment with any kind of drug has shown that you rarely get something to work the same way 100% of the time for every person. This sounds promising, but it doesn't sound like a cure to me, at least not yet.
Especially if it has only shown to work on 50% of rats, was there any human testing done as of yet? What happened to the other 50% of the rats? Death?