Sophisticated technology that packages medicines, sends them into the body and releases them as required has the potential to transform life for people with macular degeneration and a range of other serious diseases.
If medicines could be designed in a way that allowed them to be sent to the right part of the body for optimal effect, where they could sit safely until the release of controlled amounts was activated by a beam of laser light, the benefits for people who need frequent injections would be immense.
Among those most likely to cheer on research bringing this remarkable concept closer to reality are people with macular degeneration. Treatment for this leading cause of blindness often involves monthly injections into the eye.
“The drugs for macular degeneration are expensive and need to be administered roughly once a month because they don’t last very long in the eye,” says materials science specialist Associate Professor Benjamin Boyd from the Monash Institute of Pharmaceutical Sciences.
Associate Professor Boyd is working on a way to ensure the correct dose of medication gets to where it needs to go, using methods that may also reduce the number of injections needed. This research, supported by the Australian Research Council through a Future Fellowship grant, focuses mainly on macular degeneration, but also holds promise for people with other diseases, including cancer and diabetes.
His concept, developed in collaboration with colleagues from the University of South Australia, the Australian Synchrotron and the University of Western Australia, is an injectable implant that uses the unique properties of lipids – fat-like materials that are a key component of cell walls.
“It’s about controlling the structure of materials to improve medicine and drug behaviour and drug delivery,” he says.
“When lipids are in water they form different structures. Some have a closed structure and some have an open structure. We can put the drug into the closed structure and the drug won’t leach out or it will only leach out very slowly. But if it’s in the open structure, the drug can diffuse out of the material quite quickly.”
The drug-carrying materials would sit dormant in the body until required.
“The trick – where the smart science comes in – is designing systems where we can switch between the two structures when we want to,” Associate Professor Boyd says.
This would be achieved by shining an external laser beam on the appropriate site, causing the light-sensitive materials to change to the open state and release a predetermined dose of the drug.
For people with macular degeneration, this carries the welcome promise that monthly injections into the eye – with their associated risk of infection – could be replaced by an annual injection and monthly laser treatment.
About one in seven people aged over 50 are affected by some degree of macular degeneration. In the most serious form, ‘wet’ macular degeneration, excess blood vessels grow into the retina and leak fluid and blood. This damages the photoreceptors and can cause either progressive or rapid loss of vision. Drugs are injected into the eye to shut down the leaky blood vessels, helping to preserve sight.
In one form of treatment Associate Professor Boyd is developing, the drug and lipids would be combined in an oil-like liquid that would solidify as a tiny lump at the back of the eye, where it would not interfere with vision. When required, a laser shone onto the back of the eye for a few seconds would release the correct amount of medication from the implant.
Better medicines by design
Another option Associate Professor Boyd and colleagues are investigating is administering the injection under the skin rather than into the eye. The aim is for the drug-lipid structures, which are designed to avoid detection by the body’s defence mechanisms, to find their way to the site of damage. The blood stagnates at the leaking vessels, so the drug would accumulate there.
In either case, bypassing the eye’s natural defence systems is problematic. “The eye has a lot of systems in place to stop things getting from the blood into the ocular tissues,” Associate Professor Boyd says.
Because leaky blood vessels are not confined to eyes, but are also found inside tumours, cancer is another potential candidate for a similar approach to drug delivery. In fact, an existing cancer drug already takes advantage of such vessels in breast and other cancers to send anti-cancer agents into the heart of the tumour.
People affected by another major public health issue, diabetes, could also gain from the lipid encapsulation and light-activation approach to drugs.
“With diabetes, you may need to have four to five injections a day so one opportunity that this technology might offer is you have one injection a day and activate the release of insulin with a pen laser,” Associate Professor Boyd says. “The idea is that the time for which the laser is applied to the site of injection determines the amount of drug released.”
His research continues, with pre-clinical testing giving him scope to finetune the properties of the material he uses to ensure the right amount of a drug is released when required.
“We’ve got this catchphrase, ‘better medicines by design’, so it’s not necessarily about finding new drugs,” he says. “It’s about improving them.”
