Abstract: Formulations containing pH-sensitive nanoparticles for the enteric delivery of therapeutic agents are provided. The nanoparticles include a pH-sensitive polymer that protects the therapeutic agent against degradation in the stomach and allows it to be released in the small intestine or colon. The nanoparticle formulation is particularly effective at protecting sensitive biotherapeutic agents from degradation when administered orally, and makes it possible to avoid administration of such agents by injection. Also provided are methods for producing the formulations, as well as methods of treating diseases employing the formulations.