Adobe CC Audition, Under the Effects Tab, there's a variety of tools I've been working with. Sometimes one thing like the Noise Reduction might be effective. Other times it's playing with the EQ. I'm by no means an expert on it, but it can be lessened. I'm using Audition now to work on S02-F THE SHOVEL OF KAHLESS for Project: Potemkin.
Thanks for the advice! I had a problem with ADR echo on a low budget film I produced. After visiting online forums, my impression is that it's very difficult to remove echo from indoor walls, etc.