Protect it where?
If you mean just in the App Store, you might want to stage it now in ITC, with your name of choice, and make sure it's not already taken. And if you've searched the App Store and think it's available just because it didn't pop up...think again.
It it is first come, first served (copyrighted names/titles another story). Whenever you decide on a name, add a new app with the minimum info & placeholder images first thing in your process.
In the App Store, it's a bit like domain names with more than just all the good ones already taken, and with all the devs hard at work, you might be surprised which ones are already 'parked'.
If you want one and it's already in use, even if the app isn't in the store yet, Apple won't release who has it, so don't think you can ask to find out and then try to contact and negotiate.