Advances in the oral delivery of proteins

Due to their low oral bioavailability, most protein drugs are only available as parenteral formulations. The oral delivery of proteins is challenging and has often been considered an unattainable goal; nevertheless, the efforts to develop oral formulations of proteins continue to be numerous. The approaches devised to overcome the obstacles for the absorption of proteins from the gastrointestinal tract are various, and include the co-administration of enzyme inhibitors and/or absorption enhancers, the encapsulation in liposomes, microemulsions, or biodegradable particles, and the modification of proteins through the attachment of chemical moieties. This article reviews the recent patent literature related to formulation strategies to improve the oral bioavailability of proteins.