Remember this word: PoLi. It stands for polymer lipid. It took scientists four years to develop. And if everything goes as planned, it will be implanted into the bodies of ovarian cancer patients in five years time.
PoLi is the latest device to emerge from a U of T lab that specializes in drug delivery systems made out of polymers-long chains of sugar molecules. Dr. Christine Allen, a polymer chemist, and Dr. Micheline Piquette-Miller, a molecular pharmacologist, and graduate student Justin Grant spent four years taking PoLi from an idea into a promising treatment for ovarian cancer.
Conventionally, patients with ovarian cancer often undergo surgery to remove tumours, then chemotherapy to kill any remaining cancer cells. Besides hair loss and fatigue, the potential side effects of chemotherapy include hypersensitivity to the drug, or cancer cells developing a resistance to it.
Grant explained that if anti-cancer drugs are administered directly to the tumour site, a number of problems can arise.
“Dose-dumping may occur, where you have too high [of a] drug concentration, causing toxicity and also maybe leading to drug resistance,” said Grant. “The drug may also get cleared from the area too fast.”
The researchers explained that PoLi, a soft, flexible strip, delivers a sustained release of anti-cancer drugs directly to a tumour site over several months, and avoids such problems.
“Compared to conventional dosing, studies to date indicate that treatment strategies using this novel drug delivery system prevent the development of multi-drug resistance,” said Piquette-Miller, who identified the types of cancers PoLi would be best suited to treat. The system is being considered for treating solid tumours in the head, neck, breast, and prostate.
A PoLi implant is formulated to last for a specific amount of time, delivering the powerful drugs paclitaxel and carboplatin to the tumour site and breaking down naturally afterwards. Because PoLi is made of a matrix of chitosan (a natural material derived from crustacean shells) and fat molecules, it dissolves harmlessly into the body.
Gliadel Wafers is a similar implantable polymer-based system made by Guilford Pharmaceuticals to treat brain tumours. Like PoLi, these dime-sized wafers are inserted into the tumour site after surgery removes the tumour.
However, PoLi is made from cheap, natural materials, and is much less expensive to produce. Grant hopes PoLi will become an economically-sound complement to other cancer therapies.
Besides being the second most abundant polymer in the world, chitosen also has natural wound-healing properties, a trait that the team has taken advantage of in their design of a cream to assist healing. They have also developed an injectable gel with similar formulations for treating ocular diseases.
With the patent for PoLi approved and encouraging results from tests on mice already published, the group is hoping for industry funding of clinical trials. Innovations at U of T, the university’s liaison between labs and industry, has brought several interested companies to the group’s attention, but financial arrangements have yet to be made.
