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Brie Larson, Juno Temple and Greta Gerwig are also signed up for the movie, which is being helmed and scripted by Squid & The Whale director Noah Baumbach.
The story follows a New Yorker (Stiller), who moves to LA to housesit for his brother and reassess his life, only to end up having a relationship with his sibling's assistant (Gerwig).
Ifans will play Stiller's best friend, who is going through a divorce, while Larson is cast as a "college-age temptation".
Shooting is scheduled to begin later this month.
