Sex And The City 2 star and gay marriage advocate Cynthia Nixon is heading to Showtime's The Big C, Nikki Finke's Deadline Hollywood first reported.

Nixon has signed on for a recurring role on the series as Laura Linney's former college roommate, Rebecca.

The new dramedy follows Cathy (played by Laura Linney) who decides to live life to the fullest after she's given a terminal cancer diagnosis. Broadway veteran Oliver Platt (Guys and Dolls) stars as Linney's well-meaning but juvenile husband, while Gabourey Sidibe (Precious) plays the role of a smart-alecky student.

Nixon and her girlfriend, New York education activist Christine Marinoni, announced their engagement last year as New York lawmakers geared up to debate a gay marriage bill. The couple campaigned heavily for passage of the bill, appearing often at rallies and demonstrations. Senators, however, rejected the bill, leaving the women unable to marry in the Empire State.

Speaking to USA Today's Ann Oldenburg last month, the couple said they have their hearts set on marrying in New York.

Showtime will premiere The Big C on August 16 at 10:30ET.