Twentieth Century Fox is backing out of a planned deal to co-finance and distribute film and television projects from Joe and Anthony Russo, Variety has learned. The brothers had a hand-shake agreement with Fox, but the two sides were unable to come together on final terms when they were negotiating on the long-form of the deal. A source close to the negotiations said that the Russos were looking for richer financial terms than the ones the studio offers to top directors such as James Cameron and Steven Spielberg. The source said there were issues related to the structure of the deal, with Fox coming to believe that it would be asked to shoulder too much of the financial risks associated with the projects.

The Russos are big names in Hollywood, having overseen “Captain America: Winter Soldier,” “Captain America: Civil War,” and the upcoming “Avengers: Infinity War.” The two have been looking ahead to a post-Marvel life. As part of that effort, they’ve been building up an ambitious production company, and have already started to option materials, as well as opened an office in downtown Los Angeles.

Twentieth Century Fox chairman and CEO Stacey Snider sent an email to the brothers on Monday saying that the studio was walking away from the deal and ceasing negotiations, according to a person familiar with the correspondence. She went on to say that she wished the Russos the best in building their company and was looking forward to seeing the movies they made. She closed by noting that if there were individual projects that made sense for Fox, “the door to the studio was wide open.”

Last month, the brothers spoke to Variety about their ambitions for the deal. They said they were hoping to develop projects for Fox through their production company that would, in Joe Russo’s words, span “little movies, big movies, hard R, edgy films, arty films and big giant tentpole movies.”

A spokesperson for the Russo brothers could not immediately be reached for comment.