Researchers from Queens University in Belfast, Ireland, have developed a technique that uses light to turn a pro-drug into an active pharmaceutical via a photochemical reaction and precisely control the timing and amount of drug formed. The research, published as an early view article in the Journal of the American Chemical Society (JACS) shows how pro-drug molecules containing a carboxylic acid group can be turned into ester-containing drugs simply by shining a light source on them. While using light in various photodynamic therapies has met with considerable success for cancer therapies and even MRSA antibiotics, the ability to precisely control drug doses to a target area has remained elusive. This new drug release process begins when light falls on the compounds, and lasts only as long as the light continues to shine. According to Dr Colin McCoy, lead author of the study, the paper is the first step towards a new type of system makes use of our ability to precisely control light to deliver accurate amounts of drugs. "Because light is so easily controllable we could potentially control the dose released down to the level of a single drug molecule," said Dr McCoy. One of the key advantages of the approach is that drugs could be delivered at the site where they were needed without needing to expose the entire body to drugs, dramatically reducing the potential for adverse side effects to occur. "Because we can all understand light switching on and off, being able to translate that to the dose of drug released makes the concept appealing and hopefully we'll be able to make a clinical difference and start helping patients to receive better treatments with fewer side effects," said Dr McCoy. He was keen to stress that the research was still in the in vitro development stage and that they were currently looking for ways to develop the technology for clinical use. "We're currently thinking that rather than letting the drugs circulate the whole way round the body, we could incorporate them into medical polymers that could be placed at the site of diseased tissue," said Dr McCoy. He mentioned that one of the first applications the group was looking at was the delivery of drugs from medical devices which can often suffer from bacterial growth after implantation. Being able to deliver the drugs only if needed would not only help reduce the number of devices that needed to be removed because of infection, but also help reduce the build up of antibiotic resistance. "We would love to get an automatic feedback system that could read the clinical need for a drug, decide how much drug is needed and deliver the required dose - that sort of device would be quite a long way in the future," he said. The researchers are currently looking at expanding the technique to classes of drug molecule other than the ester-containing systems studied in the paper. The systems would produce drugs whenever they were exposed to light so the final manufacturing steps would need to be conducted in dark areas with the systems being packaged in silver foil type containers.
