The company paid $1 million to distribute the drama about a couple's struggles with Alzheimer's disease, Daily Variety reported.
The film, Polley's directorial debut, premiered Monday at the Toronto festival.
"It'll be both a critical and audience favorite, so our intention is to open it in the spring, let it play the entire summer, and then we'll have the DVD release in the fall," said Lionsgate President Tom Ortenberg. "And, if all goes well, that'll be well timed for an awards push."
Lionsgate followed the same strategy when it acquired "Crash" in Toronto two years ago. "Crash" won the Oscar for Best Picture in 2005.