Before THQ went bankrupt, former Ubisoft developer Patrice Désilets started working on a title called 1666: Amsterdam. As fate would have it the rights to the game later landed with none other than Désilets' former employer, and for a brief period the creator of the Assassin's Creed series was back with Ubisoft.
Shortly after that, though, he was fired, or at least that's what he claims, and for a cople of months the parties fought one another through the legal system. The end result was Désilets leaving to form is own studio, while Ubisoft retained the rights to the game.
Since then we have not heard anything about the project, but it seems it's not dead. On the contrary, a trademark was filed with the US Patent and Trademark office on April 13. We have had problems finding this filing ourselves, but luckily Dual Shockers made a screen capture of the initial registration.
The registration puts "1666" in class 9 (game software), which coincides with a previous listing from February 2012, where the title "1666" was categorised as both class 9 and class 41 (online component to game software).