WB: Joaquin Phoenix will start out as Arthur Fleck in 'Joker'

Sept. 19 (UPI) -- Warner Bros. said its Joker origin story will follow Joaquin Phoenix's Arthur Fleck as he transforms into Batman's greatest foe.

Todd Phillips -- who is directing and producing the project from a screenplay he co-wrote -- shared on Instagram last weekend the first photo of Phoenix as the character. The image showed an unsmiling Phoenix wearing rumpled attire. It was captioned "Arthur," but Phillips' post contained no other hints about the eventual villain or the film's plotline.

"Joker centers around the iconic arch-nemesis and is an original, standalone story not seen before on the big screen," the studio said in its first synopsis for Joker. "Phillips' exploration of Arthur Fleck, a man disregarded by society, is not only a gritty character study, but also a broader cautionary tale."

Filming is now underway. Co-starring Robert De Niro, Zazie Beetz, Bill Camp, Frances Conroy, Brett Cullen, Glenn Fleshler, Douglas Hodge, Marc Maron, Josh Pais and Shea Whigham, the movie is set for theatrical release Oct. 4, 2019.