Until now and Up to

Until now adverb - Used in negative statement to describe a situation that has existed up to this point or up to the present time.

Up to and until now are semantically related. In some cases you can use "Up to" instead an adverb phrase "Until now".

Up to adjective - Busy or occupied with.

Until now and up to are semantically related. Sometimes you can use "Until now" instead an adverb phrase "Up to".