According to Slash Film, Gaiman recently took to Twitter to talk about this early version of Doctor Strange, and the reason the film ultimately never went into production:
So it looks like before Marvel began production on their current iteration of the Sorcerer Supreme with actor Benedict Cumberbatch, Gaiman and del Toro had pitched the idea to the studio. Gaiman expresses particular interest in writing the role of Clea, who in the comics is a fellow sorcerer and love interest to Stephen Strange.
Rumors about this project have persisted for quite some time, but this is the first indication that Marvel Studios definitively passed on the project. Given the pedigree for both Neil Gaiman and Guillermo del Toro to create projects that delve deeply into the world of the mystical and the absurd, we can only imagine that the project would have been the stuff of legends.
This is not the first time that del Toro has run into trouble while trying to get a superhero comic book adaptation off the ground. Just a few months ago the director opened up regarding his experience with the Justice League Dark movie that has found itself in perpetual development hell. Despite spending years in development, when Warner Bros. finally came around to liking the script and the central idea behind the film, they wanted production to coincide with the production of Pacific Rim 2. In the end, del Toro opted to continue work on his kaiju sequel rather than persist with Justice League Dark – to the chagrin of comic book fans all over the world. Despite the fact that the genre seems right up his alley, the closest del Toro has gotten to a mainstream superhero film is the often underrated Hellboy franchise.
We cannot exactly say we are disappointed. What little we have seen of Scott Derrickson’s Doctor Strange looks promising, but at the end of the day we will always wonder what the film would have looked like if Gaiman and del Toro had gotten their way. Doctor Strange is expected to come to theaters on November 4, 2016.