This study is a multicenter, Phase III, randomized, placebo-controlled, double-blind study designed to evaluate the efficacy and safety of RHB-104 compared to placebo to treat subjects with moderate to severe CD. RHB-104 consists of 3 antibiotics with activity against Mycobacterium avium subsp. paratuberculosis (MAP), a potential cause of CD. Subjects with active CD will be randomized at baseline in a 1:1 fashion to receive up to 52 weeks of RHB-104 or placebo.