May 2006

Implantable Medication

Programmable drug chips have passed a longevity milestone: six months of drug release.

By Erika Jonietz

A wireless signal from outside the body prompts the device to melt a thin metal membrane, releasing a drug into the tissue. A solder seal holds the drug in place. Courtesy of MicroChips.

Implantable devices being developed by a Bedford, MA, company called MicroChips may one day replace the tedious ritual of regular drug injections. Instead, doctors could program a chip under the skin, allowing drug doses to be released on schedule from any of 100 microscale drug reservoirs.

The company took its first step toward proving such a device is possible in March, when results of the first animal test of an implantable drug-delivery system were published. MicroChips scientists showed that such devices stably released a biological drug in dogs for up to six months -- an unprecedented feat.

About the size of an Oreo cookie, the device used in the test consists of a silicon and glass microchip that contains 100 miniature drug reservoirs, each about 50 micrometers wide at the top, plus a battery and electronics controlling drug release, sealed in a titanium case.

Such a device would have obvious benefits for diabetics but could also provide a sophisticated delivery method for almost any type of drug. "This is a major step forward in drug delivery," says Henry Brem, director of neurosurgery at Johns Hopkins University School of Medicine.

Brem highlights brain and spinal tumors as an area that might particularly benefit. He hopes that such a device might be useful in his own efforts to create a tumor vaccine for brain cancer patients. A microchip could release steroids, to control brain swelling, as well as a standard course of targeted chemo-therapy drugs directly into patients' brains after a single surgery.

The device tested in dogs was activated wirelessly, and is poised for further improvements. John Santini, cofounder and president of MicroChips, says that before human tests are launched, the device will be further miniaturized -- to about the size of two stacked 50-cent pieces -- and built to last at least one year. Like the tested device, it will be programmable, so external activation of the drug reservoirs won't always be required.

The company plans to use the same basic design to create long-term, implantable sensors to monitor blood sugar levels in diabetics. Such sensors could also trigger drug release. MicroChips hopes to test these sensors in people within three years; a drug delivery device might reach human trials within five years.

Home page image courtesy of Christopher Harting. Caption: An Implantable MicroChips device, about the size of an Oreo cookie (but made of titanium).