It was adapted into an animated movie in 1982, The Secret of NIMH, which was Don Bluth’s (An American Tail, The Land Before Time, Anastasia) directorial debut.
MGM has had the book rights since 2015, and now the new movie has a director in visual effects supervisor James Madigan.
The Rats of NIMH is said to be a CGI/live-action hybrid, incorporating digital rats and mice into the real world of farmers, labs, and scientists.
One of the writers of the Transformers and Ring franchises is producing it, and Madigan has no previous directorial work, so who knows, really.