Possibly take the wheel off, break out a Dremel (if you have one) or hack saw and create a slot to accept a flat head screw driver.

Then use a impact wrench (air operated or the hand held kind) to back out the piece. I am assuming that the stud is threaded into the hub assembly?

Usually drilling out with a slightly smaller bit will get the piece to move when you are close to going all the way threw. Heat really helps here which the drilling provides.