The Hollywood Reporter, which first reported the news, explains that Feldman left ahead of a deal with ABC Studios to work on multiple projects for pilot season.
Melvoin is a five-time Emmy nominee who is best known for his work on Northern Exposure, Army Wives, Alias and Hill Street Blues. He is also the third showrunner for Designated Survivor this season. Amy B. Harris (The Carrie Diaries) was the original showrunner of the ABC drama, but was replaced by Feldman once the show scored a series pickup.
Designated Survivor stars Kiefer Sutherland as a low-level U.S. cabinet member who becomes president after a deadly attack during the State of the Union. Italia Ricci, Kal Penn and Maggie Q also star.
Designated Survivor airs Wednesdays at 10/9c on ABC.