Supposedly, you can play offline, but only the Tutorial. You play with your current customized Predator. Not sure if you can play a solo Private Match offline or not. However, you can play a Private Match solo as either the Predator or one of the Fireteam members. This way you can practice and level up quickly.
NOTE This is with the Trial version. Not sure if you'll be able to do this on the full version or not. Hopefully, the game's developers will expand on this and add an option to play offline.