Ticks provide anti-clotting drug
27 August 2009 by Marion O'Sullivan
Scientists have tapped into nature's medicine chest to develop a new drug that can control blood flow and prevent clotting, potentially preventing a stroke or heart attack.
The UK and Slovakian research team discovered and isolated an anticoagulant, or anti-clotting agent, from the salivary glands of ticks. They believe the ticks secrete the anticoagulant to keep their host's blood flowing while they feed.
Recognising the potential for this natural anti-clotting agent, which they called Variegin, the researchers teamed up with experts in snake venom peptides from the National University of Singapore, who used chemical synthesis to reproduce Variegin and make it more potent.
"By synthesising and modifying the anticoagulant our partners in Singapore were really able to understand how it works and to improve its functions," explains Professor Patricia Nuttall from the UK's Centre for Ecology & Hydrology. "As well as enabling blood to flow freely, we may now be able to stop the effect so that clotting is restored. This is an important breakthrough as it will potentially enable the development of new blood-controlling drugs with a much better performance level - and therefore fewer adverse side effects - than some of those currently available."
Snake venom expert Professor Manjunatha Kini at the National University of Singapore thinks that, although ticks have developed very potent and specific anti-clotting molecules that allow them to freely enjoy their blood-sucking lifestyle, there is still room for improvement. "By understanding how Variegin works we were able to reduce its size and at the same time improve its potency with suitable modifications," he says.
They now have molecules of different sizes, levels of potency and duration of effect. "One of the molecules has 70 times more potency and anti-clotting effect than a drug that is currently on the market," says the National University of Singapore's Dr Cho Yeow Koh.
To test the performance of Variegin, the scientists carried out initial tests on zebrafish. They used a model established by Dr Pudur Jagadeeswaran from the University of North Texas to see if Variegin could prevent venous thrombosis - and subsequently be used to prevent deep vein thrombosis in humans.
"The tests were a huge success and completely inhibited thrombus formation, "says Nuttall. "We still have a long way to go but if we can get Variegin into clinical trials it could have potential applications for coronary diseases, deep-vein thrombosis and be applied during major surgery to control bleeding. There is also evidence that, by controlling blood flow and clotting, the spread of some cancers could be diminished or prevented."
The team has filed patent applications to protect its development of the technology and is now taking steps to get Variegin out of the laboratory and into the marketplace. It is the subject of an international agreement between NERC, the National University of Singapore and the Slovak Academy of Sciences.