"Certainly there's so much to mind crumb in the book that there could be," said Pitt.
Based on the novel by Max Brooks, World War Z stars Pitt as a United Nations employee who must find a way to stop the pandemic that's defeating armies and collapsing governments.
"It's big summer fun," said Pitt, who has called the movie the best summer film he's ever done. "[The fans] were really having fun tonight and we're just really happy that that's the response we're getting."
15,000 fans gathered to hear Muse rock out for the U.K. event. The band contributed to the film's soundtrack and got Pitt's stamp of approval during the concert.