Oxygen is said to be an alien drama in the vein of District 9, about an epic romance between a girl and an alien boy when he and eight others of his kind are integrated into a suburban high school 10 years after they landed on Earth and were consigned to an internment camp.
The Hundred is set 97 years after a nuclear war has destroyed civilization. A spaceship housing the lone human survivors sends 100 juvenile delinquents back to Earth to investigate the possibility of re-colonizing the planet.
As Deadline notes, the CW is going for a more sci-fi based approach this coming Fall.
An "untold story" adaptation of Mary Queen of Scots is also in the works for this Fall at the CW.