James was reportedly among the guests at a birthday party for director Nicholas Jarecki, hosted by Pattinson at his Los Feliz, California, home on Saturday, the Poeple magazine reported.
The other high-profile people who attended the party included 'Hangover' star Heather Graham, Michelle Rodriguez, Ellen Page and Warren Beatty.
Pattinson is among the stars whose name has been doing the rounds for the coveted role.
Sam Taylor-Johnson is aboard to direct the adaptation of the erotic thriller for Focus Features and Universal movie. Writer Kelly Marcel is currently writing the script, People magazine reported.
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The erotic novel is the first book in James trilogy and traces the relationshp between a college graduate and a business magnate.
Dubbed as 'mommy porn', the book contains explicitly erotic scenes and practices like bondage, discipline, sadism and masochism.
Interestingly, James wrote the novels as fan fiction based on the Twilight series which helped Pattinson achieve global fame through his character of vampire Edward Cullen.
Pattinson's 'Twilight' co-star and ex-girlfriend Kristen Stewart, who was once in the race to play Steele, was not present at the party.