Del Toro was incredibly close to shooting an adaptation of At The Mountains of Madness in 2011, when Universal shut the project down. They decided they weren't going to risk a $150m budget on an R rated for film which would probably need about $500m to break even.
A couple of years ago Del Toro shared a thirty second clip of pre-viz by Industrial Light and Magic. Another film to add to list of what couldn't been.