Moore is playing the role of Laurel Hester in the film, a New Jersey police detective, who was prevented by government officials from assigning her pension benefits to her partner Stacie Andree after she fell terminally ill, reported The Hollywood Reporter.
Galifianakis will play the role of Garden State Equality activist Steven Goldstein.
Peter Sollett will direct from a screenplay by Ron Nyswaner.
The role of Dane Wells, Hester's detective colleague is yet to be cast. Wells became the leader in the fight for the same-sex couple's rights after learning of Hester's orientation.