The New Mutants is spin-off series from the X-Men comic books. The New Mutants made their debut in Marvel Graphic Novel #4 in 1982 and launched their own series in 1983. Charles Xavier (Professor X) decides its time to start a new class of students at his 'School for Gifted Youth' in upstate New York. His search takes him around the globe to find his special class of teenagers with incredible abilities. The original New Mutants included Sam Guthrie (AKA Cannonball), a coal miner who generates a blast field that allows him fly, Xi'an Coy Manh (Karma), a Vietnamese girl whose ability allows her to possess a person's body, Roberto DiCosta (Sunspot) from Brazil who converts solar energy into raw strength, Danielle Moonstar (Mirage) a Cheyenne indian that can project realistic illusions into your mind, and Rahne Sinclair (Wolfsbane) the young Scott who can turn into a wolf. Since the original class, there's been several new additions and versions of the team. The first series ran from 1983 - 1991. The series was restarted by Marvel in 2003 with a whole new set of students.
Rothman doesn't mention any particulars about the New Mutant film during the interview. Fox already has plans for another X-Men First Class film and a Wolverine sequel are still in the works.
You can read classic and current New Mutant comics on Marvel's website.