I've been through this multiple times. Plenty of good advice here about getting lawyers and getting your industry together to fight the suit in a joint action. Having said and tried all that personally, I've usually got my lawyer to negotiate it down to a smaller sum of a few thousand dollars and paid it. It simply wasn't worth paying orders of magnitude more than that for a legal process in which the outcome was uns…
If don't mind, could you tell how much revenue your company was generating while it was sued? I assumed they wouldn't touch companies less than 100k revenue but if they do, I think I might want to get some patent troll insurance.
Pre-revenue startup.