Advances in Oral Administration

Oral delivery is a convenient, non-invasive and safe drug administration route, with high patient compliance. However, the oral delivery of protein and peptide drugs (PPDs) remains a huge challenge for scientists. Since PPDs need to overcome intestinal physical barriers and biochemical barriers, including poor drug permeation over the intestinal epithelial membrane and the presence of a strong acidic environment and various proteolytic enzymes, PPDs may easily be degraded. In the last decade, many attempts have been made to improve the oral bioavailability of PPDs. A typical example is the oral semaglutide approved by the U.S. Food and Drug Administration. This was a significant breakthrough for oral PPD delivery, but it still has limited oral bioavailability. To promote PPD oral bioavailability, strategies have been developed for instantaneously disrupting the intestinal epithelium, such as opening the tight junction. However, this may trigger an absorption of pathogens and toxins and result in adverse effects. Another commonly used strategy is to incorporate PPDs within nanocarriers to enhance their active transportation, but the use of various synthetic materials or toxic organic solvents during preparation may also lead to side effects. Therefore, it is crucial to seek more advanced strategies for the oral delivery of PPDs. In this Special Issue, the focus was on advances in the oral administration of PPDs through research with novelty and originality, which provided a great platform for the future of the oral delivery of PPDs.