Academy Award-winning actress Melissa Leo has withdrawn from the American Repertory Theater’s production of “O.P.C.” over “artistic differences.” The world premiere of Eve Ensler’s play is set to open for previews on Nov. 28. According to the ART, it will remain on schedule. The Globe initially learned of the change in cast in an e-mail to a reporter who had requested an interview with Leo. Katalin Mitchell, ART’s director of press and public relations, said playwright Ensler and director Pesha Rudnick were not available to comment on Leo’s departure. “I don’t think anybody wants to discuss this,’’ she said. Ensler issued a brief statement later Tuesday. “Melissa Leo is a major talent, but we were unable to agree on the direction of the character,” she said. Leo could not be reached for comment. There will be a new casting announcement by the end of the week, Mitchell said. This is the third cast change in the production. Actor Stephen Collins withdrew for personal reasons weeks before rehearsals began. It was later reported that he is being investigated for allegations of child sexual abuse. The actor hired to replace Collins withdrew for personal reasons. New cast member Michael T. Weiss was called in four days after rehearsals began. “O.P.C.” (which stands for Obsessive Political Correctness) centers on the family of a young “freegan” (played by Olivia Thirlby), who squats in an abandoned building and gets her food by going on dumpster dives. She clashes with her mother, an ambitious woman who is running for Senate. The role of the mother was to be played by Leo, who won the 2011 best supporting actress Oscar for her role in “The Fighter.”Patti Hartigan can be reached at email@example.com.