Miniature Polymerized Drug-Delivery Systems on the Horizon

Originally Published MDDI December 2003

R&D DIGEST

Erik Swain

What if all forms of injection were rendered obsolete for some medications? A researcher at Johns Hopkins University (Baltimore) is looking at ways to put some drugs into microscopic plastic spheres that can be inhaled without pain.

Justin Hanes, an assistant professor at the university's Whiting School of Engineering's department of clinical and biomolecular engineering, is trying to identify ways to find particles that will dissolve in the lungs harmlessly, with a time-release function. Most aerosols require administration three or four times a day because the lung has such a high absorptive capacity. But a polymer-based drug-delivery system inhaled in its entirety would get around that problem. Such a system would also reduce toxicity concerns because less of the drug would have to be administered.

The challenge, says Hanes, is finding polymers strong and flexible enough to ensure that the particles do not break before delivering their medication. Nor can the polymers stick together, as that might inhibit travel through air passages. And, of course, the materials cannot trigger a strong immune response, because the body would attack them before they could deliver the drug. 

The polymers may be the first specifically engineered for pulmonary drug delivery. Most of the challenges have been met, Hanes says, and all components used to create the new polymer structures are already approved in other forms by FDA for other medical applications. Existing polymers have poor properties for such tasks, he says.

The spheres may also be useful for gene therapy. Hanes and Hopkins colleagues Dennis Wirtz and Junghae Suh found that they seem to be able to carry DNA directly to the cell nucleus, which would enable them to deliver therapeutic genes. 

Eventually, the technology might be able to deliver cancer-fighting drugs only to the cells affected by the disease. Localized delivery would likely be less damaging to the immune system than systemic chemotherapy, which would allow the cancer treatment to be combined with therapy to build up a person's immune system to fight carcinoma.
 
Hanes and his colleagues hope to begin testing their first inhalation particles in animal models soon.

Hanes says he prefers to investigate lung delivery initially because it does not bring the digestive acids from the stomach into play and inhalation does not have the pain of injection. But, he notes, “the lungs are pretty sacred ground. You have to be very conservative about what you put in there.”

Copyright ©2003 Medical Device & Diagnostic Industry