It is said that Pitt and Washington are already in early talks to join the project, which is set up at Lionsgate Films, reported Aceshowbiz.
Gaghan is set to pen the screenplay in addition to working behind the lens. The film will mark the Oscar-winning scribe's most high-profile directorial stint since 2005's "Syriana".
Actor Jamie Foxx is also rumored to be interested to star in the film.
Described as a two-handler crime thriller, "Candy Store" follows a highly-trained operative who starts over his life in Brooklyn, New York as a beat cop.