'The Flash' and 'Arrow's' Andrew Kreisberg has also boarded the drama as a writer and executive producer.

CBS' Supergirl continues to add to its already impressive cast.

The DC Comics take has enlisted Grey's Anatomy alum Chyler Leigh and Homeland vet David Harewood for regular roles, The Hollywood Reporter has learned. Additionally, The Flash and Arrow's Andrew Kreisberg has joined the Greg Berlanti and Ali Adler drama as a writer and executive producer.

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The hourlong drama, which received a hefty series commitment, centers on Kara Zor-El (Melissa Benoist), Superman's cousin, who was born on the planet Krypton and escaped amid its destruction years ago. After arriving on Earth, Kara was taken in by a foster family, the Danvers, who taught her to be careful with her extraordinary powers (which she shares with her famous cousin, Superman).

Harewood will co-star as DC Comics character Hank Henshaw. In the CBS take, the character is a onetime CIA agent who now runs the Department of Extra-Normal Operations (DEO), which tracks extraterrestrial threats on Earth. In the comics on which the potential series is based, Hank Henshaw is Cyborg Superman. Harewood, whose credits also include ABC's Selfie and the feature Blood Diamond, is with APA, Conway van Gelder Grant and Authentic Talent.

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Leigh, whose credits include NBC's Taxi Brooklyn, will play Alexandra "Alex" Danvers, the confident foster sister of Kara. Fascinated by Kara's powers from a young age, Alex developed a lifelong obsession with science that inspired her to become a doctor.

Leigh is repped by UTA, manager Joannie Burstein and Stone Meyer.

They join a cast that also includes Brothers & Sisters and Ally McBeal alum Calista Flockhart as DC Comics character Cat Grant, True Blood's Mehcad Brooks as Jimmy Olsen and recurring player Laura Benanti.

Arrow and Flash's Berlanti and his No Ordinary Family cohort Adler (The New Normal) will pen the script and executive produce the drama via Berlanti Productions' Warner Bros. Television-based banner. Berlanti Productions' topper Sarah Schechter also is on board to executive produce.

Email: Lesley.Goldberg@THR.com

Twitter: @Snoodit