In 2005, while on the London set of
V pour vendetta (2005),
Natalie Portman gave a copy of the original novel to
Lana Wachowski, who became deeply interested in it. A year later, both Wachowski siblings wrote a first draft of the screenplay.
Tom Tykwer, a friend of the Wachowskis, was invited to co-author several subsequent drafts with them in the following two years, constantly keeping in mind observations by the book's author himself,
David Mitchell, while looking for international investors. In all those years, Portman was promised the role of Sonmi-451, but had to turn down the role at the last minute after becoming pregnant in 2010; however, she is given a special thanks in the closing credits.
