EXCLUSIVE: After fielding interest from multiple networks, Open, the racy new drama spec from Glee and American Horror Story co-creator Ryan Murphy, has gone to HBO, which has given it a pilot order. Casting is expected to begin shortly for filming in the fall. Open, which Murphy co-wrote with Dexter co-executive producer Lauren Gussis, is described as a modern, provocative exploration of human sexuality and relationships. It hails from Fox 21, the cable division of 20th Century Fox TV, where Murphy is under a rich overall deal. This marks the first project at HBO for 20th TV/Fox21, whose maiden project at fellow premium cable network Showtime was the Emmy-winning drama Homeland. “Gary (Newman), Bert (Salke) and I have been looking for the right opportunity to be in business with HBO for awhile, and this show represents the exact right opportunity,” said 20th TV chairman Dana Walden. “Its provocative storytelling and Ryan’s trademark production values and rich, layered characters make it a perfect fit for the HBO brand.”

Related: Ryan Murphy Shopping Hot Cable Drama About Sexuality & Relationships

Open expands HBO’s relationship with Murphy, where he is directing a passion project of his, the film adaptation of Larry Kramer’s celebrated Broadway play The Normal Heart. It is through that movie that HBO president Michael Lombardo got to know Murphy and observe his talent first-hand. Then he got the call from 20th TV and was given the Open script. “I was hooked,” Lombardo said. “I think it is a perfect marriage of an idea and execution. This is an area we’ve been talking about doing something in for some time, and Ryan did it in a way that is enormously engaging. We’re thrilled doing this project with him, Dana and Gary.”

Open revolves around five lead characters, including a married couple of thirtysomethings, the husband’s male co-worker and a woman in her 40s who is a yoga professional. Murphy said he had been bouncing ideas about a show exploring human relationships when Dante Di Loreto of his company, Ryan Murphy Prods, heard about Gussis working on a similar project and put them together. “She was great fresh voice and energy,” Murphy said about combining his efforts with Gussis. The two worked on the script in December, marking the first time Murphy had written a project on spec instead of selling a pitch. As for the spec landing at HBO: “I’m thrilled about it,” Murphy said, noting his great relationship with Lombardo through Normal Heart and calling HBO a perfect home for Open. “They have great projects, and this is really an adult show that is very frank in its depiction of sex.” But that depiction never feels gratuitous, 20th TV chairman Newman adds. “It is a very honest exploration of relationships and intimacy, and the sex feels organic to the subject matter,” he said.

HBO previously tackled the subject of relationships and sexuality with Tell Me You Love Me, though I hear Open takes a completely different approach. “It is a challenge how do talk about relationships and monogamy without feeling navel-gazing and neurotic, and (Murphy and Gussis) figured it out,” Lombardo said.

For Murphy, Open adds to an already full plate that includes three series on the air, which he co-created and executive produces: Fox’s Glee, FX’s AHS and freshman NBC comedy New Normal. A fifth-season renewal for Glee is pending, and Murphy just unveiled that the upcoming third installment of AHS will be titled American Horror Story: Coven and will star Kathy Bates in addition to Jessica Lange, Sarah Paulson and Taissa Farmiga. Additionally, CAA-repped Murphy is working on Normal Heart for HBO, with Julia Roberts and Mark Ruffalo starring.

Walden vouched full support for Murphy and is not worried by his enormous workload. “He’s demonstrated over and over that he is capable of handing volume in an extraordinary way,” she said. Gussis, repped by CAA and Circle Of Confusion, also worked on ABC’s Once Upon A Time. Fox 21′s slate includes the Emmy-winning Homeland for Showtime; FX’s Sons Of Anarchy; A&E’s Those Who Kill; and the FX pilot Tyrant, from Howard Gordon, Gideon Raff, and Craig Wright, which recently tapped Ang Lee as director.