Leo withdrew to star in David O. Russell's "The Fighter"; she will play the mother of Christian Bale and Mark Wahlberg's characters.
In a statement Leo said, "I truly regret not being able to go on with this project, which has meant so much to me. Being part of its development will always be a special memory, but how do you say no to working with Mark Wahlberg and Christian Bale? Seriously, I am terribly disappointed to not be able to take Heart of the City to the next level and wish it much success."
Producers announced May 26 that the cast will feature Eliza Foss, Scott Kerns, Marcia Jean Kurtz, Martin LaPlatney, Melissa Miller and Mark Setlock.
Eric Lane's play, directed by Martha Banta, will run through June 28.
Fern Kershon and Orange Thought Productions produce.
Performances will be Thursday, Friday, Saturday and Monday at 8 PM, with matinees Saturday at 2 PM and Sunday at 3 PM.
The Theatre at 30th Street is located at 259 West 30th Street, between 7th and 8th Avenues; to purchase tickets, priced $18, visit Smarttix.com or call (212) 868-4444.
For more information visit www.heartofthecitytheplay.com.