Avastra abandons BioWeld Tube clinical trials

Biomaterials company Avastra (ASX:AVS) is to abandon a clinical trial of its BioWeld Tube at Concord Repatriation and General Hospital, Sydney.

The clinical trial was initially halted in June, following unexpected results in an existing long-term animal study on the BioWeld Tube. Avastra's BioWeld technology joins arteries and veins using a protein solder which is currently activated by laser light.

The long-term animal trial was conducted in rats whose abdominal aortas had been anastomosed (joined) to test for long-term patency (free blood flow through the anastomosis). When culled at the end of six months, nine out of 60 ostensibly healthy rats had either blocked aortas, or no aortas at all.

The abdominal aorta is the major blood supply to all parts of the body below the lungs in mammals, and clinicians were to find rats surviving apparently without functioning aortas.

"We couldn't explain it," said Avastra's managing director, Paul Ralph. "We suspended the trial until we could get an explanation for it and see whether it poses a risk to patients."

Avastra used clinical research organisation Datapharm Australia to commission an independent panel of four medical and scientific experts to examine the research data and advise Avastra as to whether it should proceed with the clinical trial and the future direction of its research and development program.

"They couldn't come up with an explanation for the results," said Ralph. "Since we don't have an explanation and we're concerned about patient safety, we though it would be reckless to continue with the clinical trial."

The panel of experts also recommended that Avastra undertake more extensive histopathological and immunological testing of its study cohorts and that future studies be conducted in animals other than rats, said Ralph.

"The rat model may not be a good model for testing the BioWeld," said Ralph -- vessel walls in rats are thinner than those in humans, and they have less smooth muscle, an important aspect in the healing process.

"We're looking to conduct studies in pigs, because they have a very comparable vascular structure, and vessel size, and immunologically they have very similar responses to humans," Ralph said.

The panel of exerts also recommended that Avastra's research and development program be regularly reviewed by an independent scientific and medical panel. "That process is in place," said Ralph. "We're assessing the costs and how to take it from here."

When asked whether he maintained confidence in BioWeld, Ralph said: "Technically, it's a competent piece of technology. However, we need to do more work to explain these results, so they don't pose a risk to humans. That's just responsible."

Avastra's BioWeld end-to-side program in sheep is scheduled for completion by the end of the year and the company has elution studies ongoing in its BioWeld drug delivery system. Any further research will be determined following advice from the external independent panel, said Ralph.

"We're investigating totally new areas. When you do that, you're breaking ground, and you get hiccups. You've got to look at why you've had these hiccups and how you can explain them."

Glues instead of lasers

Avastra has also been investigating the possibility of using surgical glues instead of lasers for its BioWeld ETS (end-to-side) device. Preliminary results in 33 rats have shown that using glues with the BioWeld Tube can join rat abdominal arteries as effectively as the best results seen to date using lasers.

Ralph said that the cell cytotoxicity commonly associated with glues is not an issue when used with the BioWeld Tube.

"The cytotoxicity [of the glue] is related to exothermic energy -- heat released from their polymerisation when they cure -- and we used such a small amount, and we've tested it, that it's not an issue," said Ralph.

The use of glues is also economically more attractive than lasers, said Ralph, and lasers are dependent on their operators.

"If we can design an applicator that can dispense the glue for those precise amounts, and control where it's being dispensed... it looks like a potentially viable proposition," he said.

Earlier this year, Avastra decided not to exercise its option to acquire the global rights to the Universitaetsklinikum Freiburg's Benz Stent technology, used for deep colorectal procedures, because of concerns about market size and clinical development time.

Avastra's sales dived more than 15 per cent yesterday to close at AUD$0.135. At press time they were trading at $0.13. In March this year they were trading as high as $0.44.