Yeah, I have a cat who my roommate 13 years ago taught to play with his hand, and let him bite and scratch as hard as he wanted. He would bite hard. It took a while, but I got him to stop by just immobilizing my hand when he started latching on, which made him lose interest and loosen his grip. I'd also give him a high-pitched "ooow" as an audible cue. Once I got my hand out I would poke his nose and say "no bites" then pet him on his forehead. Every once in a while he still regresses, but instead of biting now he almost always just aggressively headbutts your hand.