Showtime’s pilot “I’m Dying Up Here” from exec producer Jim Carrey is filling out its cast.

Oscar winner Melissa Leo is set to star in the dark comedy, Variety has learned. Sebastian Stan and Clark Duke have also joined the cast, joining previously announced talent Ari Graynor, Andrew Santino, RJ Cyler, Erik Griffin and Stephen Guarino.

Should the pilot go to series, Leo and Duke would be series regulars, while Stan would appear in a guest-starring role.

Leo (“The Fighter,” “Louie”) will play Goldie, a brassy comedy club owner who rules over her business with an iron fist and nurtures her comedians with tough love. Duke (“Hot Tub Time Machine,” “The Office”) joins the ensemble of young comedians in the project, set to play Larry, a ballsy young Boston-bred comic who moves to L.A. with the hopes of making it big. Stan (“Captain America: The Winter Soldier,” “The Martian”) has been cast as Clay, a funny and charming on-the-rise comedian who’s idolized by his ex-girlfriend, fellow comedian Cassie (Graynor).

Set in the celebrated and infamous L.A. stand-up comedy scene of the ’70s when the careers of most comedy superstars began, the pilot will delve into the inspired and damaged psyches that inhabit the hilarious, but complex business of making an audience laugh.

“I’m Dying Up Here” hails from writer and exec producer Dave Flebotte (“Masters of Sex,” “Will & Grace,” “Desperate Housewives”). Carrey will serve as an exec producer, along with Michael Aguilar (“The Departed”) and Christina Wayne (“Copper”). Jonathan Levine will direct the pilot (“50/50,” “Warm Bodies”), based on William Knoedelseder’s book of the same name, from Endemol Shine Studios and Assembly Entertainment.

The pilot will shoot in Los Angeles this fall.