A new study from the University of Michigan describes one of the first entirely new microencapsulation approaches to drug delivery in decades.
Microencapsulation in biodegradable polymers allows drugs such as therapeutic peptides to be released over time in the body.
Peptides are molecules in the body made up of short chains of amino acids and include well-known messengers, growth factors and hormones such as insulin. Due to their larger size and structure, peptide drugs are rarely taken orally and must be injected. Microencapsulation is a way to reduce the time needed between injections.
One slow-release delivery method for peptide drugs is to encapsulate them in the type of absorbable polymers often used as dissolving sutures, said study co-author Steven Schwendeman, a professor of pharmaceutical sciences and biomedical engineering.
However, the development of polymeric dosage forms for the delivery of certain peptide drugs has been difficult because currently available methods for microencapsulating the peptide molecules in the polymer require organic solvents and complex manufacturing.
“The Schwendeman group discovered about 10 years ago that peptides can spontaneously bind and penetrate into the polymer from water to microencapsulate the peptide very simply without an organic solvent,” Schwendeman said.
At that time, the group showed that the concept potentially worked, but was not yet commercially useful, he said.
“This paper demonstrates that this concept can be implemented to efficiently create injectable biodegradable polymer particles that are equivalent or even improved over existing commercial products, which slowly release several different peptides over more than a month, providing one of the first entirely new microencapsulation approaches in decades. “Schwendeman said.
Schwendeman and his colleagues found that if they first made the polymer and equilibrated the peptide with the polymer microspheres in water under certain conditions, they could achieve a result very similar to the conventional method of drug encapsulation at organic solvent base.
In the current study, the researchers found that leuprolide encapsulated in this way released peptides for over 56 days in the laboratory and suppressed testosterone production in rats equivalent to a month’s injection of Lupron Depot. Leuprolide injections are used to treat prostate cancer, endometriosis, and other conditions.
This encapsulation method works with several other peptide drugs on the market and for others that have recently been approved or in development, Schwendeman said.
The group is now expanding the ability to encapsulate different types of peptides and other large drugs, delivering the drugs over longer periods of time and developing a second technique to remotely load the drugs into the polymer, which concentrates on fragile proteins.
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