The specification generally relates to compounds of Formula (I) and pharmaceutically acceptable salts thereof, where R1 has the meanings defined herein. The specification also relates to the use of compounds of Formula (I) and salts thereof to treat or prevent ATM mediated disease, including cancer. The specification further relates to pharmaceutical compositions comprising substituted imidazo[4,5-c]quinolin-2-one compounds and pharmaceutically acceptable salts thereof； and kits comprising such compounds and salts.
