No last day set yet for Jason Hirschhorn.

Jason Hirschhorn, MTV Networks' chief digital officer, has resigned his position to “explore entrepreneurial opportunities,” the company has revealed. Hirschhorn was the driving force behind MTV's Urge digital music service, launched as a public beta on May 17, among other digital and mobile strategies.

According to MTV, the transition will take place over the summer, with no set date as his last day. Effective immediately, Hirschhorn’s second-in-command, executive VP of MTV Networks Digital Nick Lehman, will take over most of his duties and will report directly to MTV Networks chairman and CEO Judy McGrath.