According to The Hollywood Reporter, although the clock is ticking down on the start of principal photography, X-Men 3, the sequel to 20th Century Fox's two X-Men features, is once again without a director.

The studio said Tuesday that Matthew Vaughn, citing personal reasons, is stepping down as director. Having produced Guy Ritchie's crime movies Lock Stock and Two Smoking Barrels and Snatch, Vaughn made his directorial debut with the critically applauded gangster tale Layer Cake. Released by Sony Pictures Classics, the $7 million movie has grossed $729,488 in its first 18 days of limited release as well as another $8 million in foreign release.

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X3 would have been Vaughn's first big-budget studio project, and the director said he was determined to bring more heart to the Marvel superhero characters, played by a cast that includes Hugh Jackman and Halle Berry.