A new NBC mid-season series is now searching for a new lead actress. According to The Hollywood Reporter, actress Maura Tierney has left the new comedy series Parenthood.

It was announced in July that NBC was moving the series from a fall premiere to mid-season after Tierney's then-undisclosed illness, which she later revealed to be breast cancer. Production was postponed until November, for Tierney to undergo treatment, but now it seems her treatment will take longer than expected.

"Ms. Tierney and her doctors remain confident that the outcome of her treatments will be positive," Tierney's spokeswoman said Thursday. "She is deeply disappointed that she will not be able to rejoin such a highly respected, talented, fun and funny group of actors and wishes to thank Jason Katims and NBC for their patience and support."

NBC is currently seeking a new lead for the series, created by Jason Katims, which was based off the 1989 Parenthood film. We'll certainly keep you posted on any new casting developments for this upcoming series as soon as more information comes in.