I can't remember the name of a childrens Sci-Fi book about apes/Gorrillas?

All i remember was there was a compound that was highly fortified and they were testing on either gorrillas/apes and the main character had to escape with a friendly intelligent ape/gorrilla and they were chased by other evil gorrillas, it would have been released in the mid nineties and it was a teen book as I had to review it for my school library any help appreciated??