sequel?

https://en.wikipedia.org/wiki/Fantastic_Voyage#Cancelled_sequel/remake_plans

"Plans for a sequel or remake have been in discussion since at least 1984, but as of the beginning of July 2015, the project remained stuck in development hell. In 1984, Isaac Asimov was approached to write Fantastic Voyage II, out of which a movie would be made.[36] Asimov "was sent a suggested outline" that mirrored the movie Innerspace and "involved two vessels in the bloodstream, one American and one Soviet, and what followed was a kind of submicroscopic version of World War III."[36] Asimov was against such an approach. Following a dispute between publishers, the original commissioners of the novel approached Philip José Farmer, who "wrote a novel and sent [in] the manuscript" that was rejected despite "stick[ing] tightly to the outline [that was sent to Asimov]."[36] "It dealt with World War III in the bloodstream, and it was full of action and excitement."[36] Although Asimov urged the publisher to accept Farmer's manuscript, it was insisted that Asimov write the novel. So, Asimov eventually wrote the book in his own way (completely different in plot from what [Farmer] had written), which was eventually published by Doubleday in 1987 as Fantastic Voyage II and "dealt not with competing submarines in the bloodstream, but with one submarine, with [an] American hero cooperating (not entirely voluntarily) with four Soviet crew members."[36] The novel was not made into a movie, however.

James Cameron was also interested in directing a remake (since at least 1997),[37] but decided to devote his efforts to his Avatar project. He still remained open to the idea of producing a feature based on his own screenplay, and in 2007, 20th Century Fox announced that pre-production on the project was finally underway. Roland Emmerich agreed to direct, but rejected the script written by Cameron.[37][38] Marianne and Cormac Wibberley were hired to write a new script, but the 2007–2008 Writers Guild of"