Lipid Nanocarriers Could Enable an Oral Pill Form of the Immune-Boosting Peptide Thymopentin | Research

The takeaway

Lipid-based nanocarriers combined with enzyme inhibitors protected the immune peptide thymopentin from gut degradation for 6 hours, paving the way toward an oral formulation that could replace injections.

6 hours of gut protection
All three lipid-based nanocarrier systems protected thymopentin from digestive enzyme degradation for 6 hours — far longer than the unprotected peptide survives — bringing an oral pill form of this injectable immune therapy closer to reality.

What the researchers found

TP5 degradation followed pseudo-first-order kinetics and was primarily driven by luminal enzymes throughout the intestinal tract (duodenum, jejunum, ileum, and colon). Three enzyme inhibitors significantly reduced TP5 breakdown:

- Soybean trypsin and chymotrypsin inhibitors (SBTCI) — considerable decrease in peptidolysis

- Bestatin — significant reduction

- EDTA — significant reduction

Three lipid-based nanocarrier systems (microemulsions, niosomes, and solid lipid nanoparticles) loaded with TP5 and SBTCI provided superior protection against degradation by both luminal contents and mucosal homogenates for 6 hours, compared to the unprotected peptide in solution.

Why it matters

Most peptide drugs must be injected because the digestive system destroys them before they can be absorbed. This is a major barrier to patient compliance and quality of life. Thymopentin is an immunomodulatory peptide used to treat immune deficiencies, autoimmune conditions, and as an adjunct in cancer therapy. Developing an oral form could make it accessible to far more patients and improve adherence, while the approach itself could be applied to other therapeutic peptides facing the same delivery challenge.

How the study worked

Researchers extracted mucosal and luminal components from four sections of rat intestine (duodenum, jejunum, ileum, colon) and measured TP5 degradation kinetics with and without these components. Three enzyme inhibitors (EDTA, SBTCI, bestatin) were screened for their ability to block TP5 breakdown. TP5 with the best inhibitor (SBTCI) was then loaded into three lipid-based nanocarrier systems. These were characterized for morphology, particle size, zeta potential, and entrapment efficiency, then tested for TP5 protection in ex vivo intestinal degradation studies.

What this study cannot tell us

All experiments were conducted ex vivo using rat intestinal tissues, which may not perfectly replicate human gastrointestinal conditions. No in vivo oral absorption or bioavailability data were generated. The entrapment efficiency and long-term stability of the nanocarrier formulations are not discussed in detail. The transition from ex vivo protection to actual systemic absorption in a living organism involves additional barriers (mucus layer, epithelial transport) not addressed here.

How to read the evidence

This is an early-stage pharmaceutical formulation study using ex vivo rat intestinal models. While the results demonstrate proof of concept for protecting TP5 from gut degradation, no in vivo oral absorption or clinical data are presented. This is preclinical drug delivery research.

When this study was published

Published in 2022, this study is recent and contributes to the active field of oral peptide delivery, building on the success of oral semaglutide and the growing demand for needle-free peptide therapeutics.

The bigger picture

Oral delivery is the holy grail of peptide drug development. While semaglutide (Rybelsus) proved that oral peptide delivery is possible, most peptide drugs still require injection. This study contributes a systematic approach — mapping degradation sites, identifying effective inhibitors, and engineering protective nanocarriers — that could be applied broadly to other therapeutic peptides. The combination of enzyme inhibitors with lipid nanocarriers represents a multi-layered protection strategy.

Questions still open

Which of the three lipid nanocarrier types (microemulsions, niosomes, or solid lipid nanoparticles) performs best in actual in vivo oral bioavailability studies?
Can this combined inhibitor-nanocarrier approach achieve clinically meaningful plasma levels of TP5 after oral administration?
Could the same lipid nanocarrier strategy be applied to protect other therapeutic peptides like insulin or calcitonin for oral delivery?

Common questions

Why can't peptide drugs like thymopentin be taken as pills?

Peptide drugs are made of amino acids, which are the same building blocks the body digests from food proteins. When taken orally, digestive enzymes in the stomach and intestine rapidly break peptide drugs apart before they can be absorbed into the bloodstream. That's why most peptide drugs — including thymopentin, insulin, and many others — must be given by injection, bypassing the digestive system entirely.

How do lipid nanocarriers protect peptides from digestion?

Lipid nanocarriers are tiny particles made from fats that encapsulate the peptide drug inside a protective shell. In this study, three types were tested: microemulsions, niosomes, and solid lipid nanoparticles. Combined with enzyme inhibitors (derived from soybeans), these nanocarriers shielded thymopentin from digestive enzymes for 6 hours. The lipid shell physically blocks enzymes from reaching the peptide, while the inhibitors deactivate the enzymes in the surrounding environment.

Read the original research

Exploring ex vivo peptideolysis of thymopentin and lipid-based nanocarriers towards oral formulations.

International journal of pharmaceutics, 625, 122123

View on PubMed ↗Publisher’s paper ↗

Citation

Liu, Mengyang; Svirskis, Darren; Proft, Thomas; Loh, Jacelyn; Chen, Shuo; Kang, Dali; Wen, Jingyuan. (2022). Exploring ex vivo peptideolysis of thymopentin and lipid-based nanocarriers towards oral formulations.. International journal of pharmaceutics, 625, 122123. https://doi.org/10.1016/j.ijpharm.2022.122123