Bionomics hails new class of epilepsy drug

An Australian research study published this week in the prestigious journal Proceedings of the National Academy of Science explains why current drugs don't work on a common, inherited form of epilepsy -- and points the way to a new class of epilepsy therapeutics.

Researchers from Adelaide-based biotechnology company Bionomics (ASX: BNO) and Melbourne University, led by Dr Steve Petrou, have shown that absence epilepsy is caused by a defective ion channel that normally inhibits nerve activity in the brain.

The affected neurons become hyper-excitable and fire uncontrollably, triggering a temporary absence of awareness in the patient.

The mutation affects a part of the protein molecule that lies outside the site where standard anti-epileptic drugs dock with the receptor. In consequence, patients experience some of the normal -- and unwanted -- effects of the drugs, but receive no relief from their epileptic seizures.

"Steve Petrou has found these drugs are actually less than helpful for absence epilepsy patents," said Bionomics CEO Dr Deborah Rathjen. "Now that his group has defined the binding site, it gives us a strategy for selecting compounds that will specifically target the affected site. It takes us into an entirely new class of compounds. "We're interested in screening other classes of drugs that are known to bind to the ion channel.

"We now have some structural information about how the mutation affects the structure of the site, so we may also be able design synthetic molecules to bind to it.

"What's exciting is that the research is starting to be translated into clinically useful approaches."

In October Bionomics completed a deal with [Nasdaq-listed, San Diego-based biomedical company] Nanogen to develop the first molecular diagnostic for epilepsy.

The Nanogen test, used in conjunction with conventional epilepsy tests, based on clinical symptoms, will lead to more accurate diagnosis of absence epilepsy, Rathjen said.

In an announcement today, Bionomics said the PNAS paper validated a key component of its IonX discovery platform.

All but one of the mutant genes involved in inherited epilepsies have been found to code for ion channels -- molecular valves in nerve-cell membranes that regulate the flow of charged metallic atoms through cell membranes.

Rathjen said epilepsy was a serious illness, affecting about 8.2 people in every 1000 in the general population. Some 30 per cent of patients do not respond to current anti-epilepsy drugs. Around 180,000 new cases are diagnosed each year.

The market for epilepsy drug treatments is worth around $5 billion per year.