I think repeating what you are doing and telling him it hurts you and that you are sad will sink in. If someone else is around when it happens, doing what Spring Angel suggested and what Bathsheba has said a few times before, tending to the injured can be a great strategy. So, if your DH can fuss over you and say "oh, he bit you, that must hurt, I'm so sorry", that might well sink in.
My DS was doing things (a bit of hitting) and he did it a bit to my mum. After a period of 'tending to the injured', DS started to say 'sorry' and hasn't hit for a while. We revert to this policy as necessary, though.
It models empathy and focuses on the effect of what they've done and the consequences to the other person, rather than on them and their behaviour (the latter means it becomes about them and can teach them to be sneakier and that it's bad if they get caught!).
It takes time, in many cases, but it means that the real lesson is taught and the novelty of trying his teeth out will wear off. I hope!!