CHICAGO USA (AP) — There was no stopping Limitlessat the box office.

The science-fiction thriller opened at Number one this weekend with $19 million, according to studio estimates.

The film from Relativity Media stars Bradley Cooper as a struggling writer who takes a magical pill that allows him to tap into his maximum brain potential. Suddenly he’s cleaned up, making millions and wowing everyone he meets. Robert De Niro costars as a financial guru who’s fascinated by him, with Abbie Cornish as Cooper’s sceptical girlfriend.

Limitless broke out of a crowded pack of new releases and holdovers to take the top spot.

Last week’s Number one, the alien invasion movie Battle: Los Angeles, fell to third place with $14.6 million. The Sony Pictures release has now made an estimated $60.6 million in two weeks. Coming in second was the animated Western Rango, featuring the voice of Johnny Depp as a chameleon who’s stuck in the desert. The Paramount film made $15.3 million for a three-week total of nearly $92.6 million.

It was a slow weekend, with the other new releases battling for the fourth and fifth spots. At Number four was the Lionsgate thriller The Lincoln Lawyer starring Matthew McConaughey as a sleazy defence attorney on a high-profile case. It made an estimated $13.4 million. In fifth place was Paul, with Seth Rogen providing the voice of a pot-smoking, wise-cracking alien who befriends a couple of British sci-fi geeks, played by Simon Pegg and Nick Frost (who also wrote the script). The Universal Pictures comedy made about $13.2 million.

Kyle Davies, Relativity’s president of theatrical distribution, said he thinks Limitless stood out this weekend through a combination of its marketing message and good word of mouth.

“This was a thriller but a very different kind of thriller,” he said. “It was a unique angle on a traditional genre.”

Davies also pointed to Cooper’s appeal as a factor in the film’s success. Limitless allowed the star of The Hangover and The A-Team to show a more dramatic side.