It is officially the movie Joker in Warner Bros.
After it was reported that Joaquin Phoenix was in talks to play the archenemy from Batman, Variety now reports that the agreement has been finalized and the study gave the green light and a September start date for production.
The original film Joker is directed by director Todd Phillips, who also co-wrote the screenplay with Scott Silver. The film has been described by the studio as an "exploration of a man ignored by society [that] is not only a gritty study but also a broader warning tale". The sources also say that the story will take place in the 80s  Interestingly there is another project Joker happening now, starring Jared Leto, who played the criminal brain in Suicide Squad . Leto has been summoned to return to the sequel, as well as, an independent film Joker separate from that of Phoenix.
The Hollywood Reporter reports that the project budget is in the $ 55 million range and could be ready for launch by the end of 2019.