The main gate to Paramount Pictures Studios, a division of Viacom, Inc. is pictured in Los Angeles, California July 29, 2008. REUTERS/Fred Prouser

LOS ANGELES (Reuters) - Hollywood studio Paramount Pictures, which suffered the first big bomb of the summer last weekend with an Eddie Murphy comedy, has fired its top production executive after barely 18 months in the job.

The Viacom Inc-owned studio said on Friday it would replace Paramount Film Group president John Lesher with former DreamWorks production chief Adam Goodman. Also out is production president Brad Weston.

Paramount, which is struggling to regain its momentum after a lengthy reliance on co-productions led to a major shakeup four years ago, did not cite a reason for the latest personnel shift in its statement.

The studio has the top film of the year so far in North America with “Star Trek,” but its slate has otherwise been boosted by films from partners such as DreamWorks Animation (“Monsters vs. Aliens”). The unrelated DreamWorks Pictures has also been a major supplier, but it quit Paramount last year, leaving Goodman behind at Paramount.

Murphy’s “Imagine That,” which Paramount said cost $55 million to make, has earned $9.2 million after eight days.

Paramount will likely top the worldwide box office next weekend with “Transformers: Revenge of the Fallen,” although the sequel is a legacy of its DreamWorks partnership.

Goodman becomes the third executive to oversee all of Paramount’s film production since studio chairman and CEO Brad Grey arrived at the studio in January 2005 with a mandate to produce more films in-house. Lesher, who had been closely involved with such Oscar-winning arthouse fare as “Babel” and “There Will Be Blood,” took over as head of the film group in early 2008.