The move had been expected since last year when Callender lost out in the race to lead HBO following Chris Albrecht's departure. The decision to take HBO Films out of the feature film business and the closure of Picturehouse may have also influenced his decision. He will announce plans for his new company in 2009.
Upon Callender's departure Len Amato will become president of HBO Films and Kary Antholis will become president of HBO Miniseries. Both will report to president of programming group and West Coast operations Michael Lombardo.
Callender first joined HBO in 1987 as executive producer of HBO Showcase after establishing himself as a film and television producer in the UK. He relocated to Los Angeles in 1999 to become president of HBO Films and consolidated HBO's existing film divisions under the new label.
'My career has been shaped by the one constant in this industry - change - and for some time I've had a hankering to return to my entrepreneurial roots,' Callender said. 'With the industry in the midst of a major transformation, and coming off this great year, I can't think of a better time to launch my own company.'
HBO co-president Richard Plepler paid tribute to Callender's 'vision, intelligence and unique talent' and said his contributions to the company had been 'nothing short of extraordinary.'
Amato has been senior vice president of HBO Films since March 2007 and served as executive producer on HBO Films' Recount. Prior to HBO he was president of Spring Creek Productions. His producer and executive producer credits include Analyze This, Analyze That, Possession, Rumor Has It, Blood Diamond and The Astronaut Farmer.
Antholis has been senior vice president of HBO Films and Miniseries since November 2004 and overseen the development and production of the HBO Films' Wit and The Gathering Storm, as well as John Adams, Angels In America, Generation Kill and the upcoming The Pacific.