Emma Stone is also in negotiations to co-star with del Toro on board to helm.
Plot details are being kept under wraps as del Toro and Lucinda Coxon rewrite the original script he penned with Matthew Robbins.
Legendary will produce and be a participating financing partner on the movie, with Universal Pictures retaining an option to finance at a later date. The film is set to begin shooting in February 2014.
Del Toro is no stranger to reteaming with actors on multiple projects, having worked with Hunnam’s “Sons of Anarchy” co-star Ron Perlman on four films including Universal’s “Hellboy” series.
Besides “Pacific Rim,” the CAA repped Hunnam just wrapped the fifth season of “Sons of Anarchy.”