Oral Delivery of Therapeutic Proteins and Peptides: An Overview of Current Technologies and Recommendations for Bridging from Approved Intravenous or Subcutaneous Administration to Novel Oral Regimens

Since the early 1980s, therapeutic proteins and peptides have become established as an important class of pharmaceuticals. Due to their low oral bioavailability, which results from pre-systemic degradation and poor gastrointestinal absorption, most therapeutic proteins and peptides are administered intravenously. While subcutaneous formulations of some therapeutic proteins and peptides have been shown to improve patient convenience and reduce medical resource utilization, oral administration is generally the preferred administration route. Some therapeutic proteins and peptides employing novel oral delivery technologies have reached late-stage clinical development. To develop a new oral formulation of a therapeutic protein or peptide currently marketed as an injectable product, technical, nonclinical, and clinical studies are required to demonstrate similar safety and efficacy compared with the existing administration route. Since there is little experience with oral therapeutic proteins and peptides, this review provides recommendations for bridging from an approved intravenous or subcutaneous regimen to novel oral administration of the same therapeutic protein or peptide, based on precedents from intravenous-to-subcutaneous bridging approaches for trastuzumab, rituximab, tocilizumab, and bortezomib. If the pharmacokinetic/pharmacodynamic relationship is well characterized, demonstration of comparability in prespecified pharmacokinetic parameters might form a basis for establishing similar efficacy and safety of the oral formulation vs. the reference product. Although oral administration of therapeutic proteins and peptides remains challenging, given recent progress with novel delivery technologies, intravenous/subcutaneous-to-oral nonclinical and clinical bridging programs may soon be utilized to support approval of new oral formulations.