James McAvoy will be playing the adult Bill Denbrough, the defacto leader of the Loser’s Club from the first movie. He’ll be joined by Jessica Chastain as Beverly, Isaiah Mustafa as Mike, Jay Ryan as Ben, Bill Hader as Ritchie, Jay Ransone as Eddie, and Andy Bean as Stan. However, we haven’t seen the last of the young actors who played the roles in the first film, as the entire group will reportedly be back, one assumes in flashbacks or some sort of prologue.
Article source: https://www.cinemablend.com/news/2465314/it-chapter-2s-james-mcavoy-was-thoroughly-freaked-out-by-pennywise-on-set