Ellender launched Slingshot in February 2014 with backing from private investor TPG Growth.
The remaining staff, which includes head of scripted programming Quan Phung and international sales chief Carol Eymery, will continue to operate as normal.
Slingshot’s projects include action series Rain, which is planned to star Keanu Reeves and a Cleopatra TV series. Neither has gone into production.
Ellender was chief executive of FMI predecessor FremantleMedia Enterprises between 2006 and 2013.