UPDATE on March 4, 2021: George R.R. Martin has posted about the development of In the Lost Lands.
“Some recent piece of development news regarding George R.R. Martin has slipped out the last couple of days. First, GRRM and Kalinda Vazquez are set to develop Roger Zelazny’s novel Roadmark for HBO. A science fiction/fantasy blend, the basic concept is of a mysterious, endless road that travereses time, space, and alternate realities that travelers can use to explore and even try to change the past, present, and future.
Martin has posted about it at his “Not a Blog”, noting that it was one of five pitches he made to HBO as part of his overall development deal with them, all of them based on notable works of science fiction and fantasy that he believed could work well adapted. Vince Gerardis, who helped package Game of Thrones, will also have a co-executive credit.