The Spartacus star will play the sexually charged sister of series lead Martina, reports Deadline.
Baby Big Shot will follow Martina (Janet Montgomery), a working-class lawyer who uses her street smarts to compete with colleagues at a top New York firm.
Cummings played Sura in the first season of Spartacus and later starred on ABC cop drama Detroit 1-8-7. She recently appeared on ABC's Pan Am in a recurring role.
Kyle MacLachlan (Twin Peaks) and Toni Trucks (Twilight: Breaking Dawn - Part 2) will also appear in Baby Big Shot.
Dana Calvo (Covert Affairs) has written the pilot, with Kevin Falls (The West Wing) serving as showrunner.
Other drama pilots in the works at CBS include Sherlock Holmes update Elementary starring Jonny Lee Miller and Lucy Liu, and a '60s-set project with Dennis Quaid, Michael Chiklis and Carrie-Anne Moss.
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