Matthew Fox was forced to bow out due to scheduling conflicts with I, Alex Cross, which starts shooting in August. It isn't known why Ed Harris stepped away from the project.
It is said that both Matthew Fox and Ed Harris had smaller roles in World War Z, but producers are trying to recast both parts rather quickly, with readings set up in Los Angeles and London.
Marc Forster is directing World War Z from a screenplay by J. Michael Straczynski and Matthew Michael Carnahan, which is adapted from the Max Brooks novel. The story is set 10 years after a worldwide zombie attack, and told through multiple perspectives of survivors around the world.
World War Z was released June 21st, 2013 and stars Brad Pitt, Mireille Enos, Daniella Kertesz, James Badge Dale, Ludi Boeken, Matthew Fox, Fana Mokoena, David Morse. The film is directed by Marc Forster.