McAvoy and Hader are in negotiations to appear as older versions of characters who were terrorized by Pennywise the Clown in the first film, released in 2017.
McAvoy would take on the role of Bill Denbrough, the stuttering leader of his friends known as the Losers Club, originally portrayed by Jaeden Lieberher. Hader would play wise-cracker Richie Tozier, originally portrayed by Finn Wolfhard.
Chastain will be featured as Beverly Marsh, the only female member of the Losers Club who was originally portrayed by Sophia Lillis. The sequel will deal with the group of friends returning to their hometown of Derry, Maine 27 years after the events of the first film to once again confront Pennywise.
Director Andy Muschietti, screenwriter Gary Dauberman and Bill Skarsgard as Pennywise are returning for the sequel. Lieberher, Wolfhard and Lillis will also be returning along with the other kid actors from the Losers Club to be featured in flashback sequences.
It: Chapter Two is set to begin production in July and will hit theaters on Sept. 6, 2019.