Antisense defended in wake of Isis trial failure

Mark Diamond, the CEO of Australian company Antisense Therapeutics, has defended antisense technology in the wake of a failed trial of the technology by US companies Isis Pharmaceuticals and Eli Lilly.

The trial, of an experimental lung cancer drug, came to an end last week with both Isis and Lilly admitting that patients taking Isis's drug, Affinitak, together with conventional chemotherapy, did not live significantly longer than those undergoing chemotherapy alone.

Isis, based in California, has staked its future on the potentially revolutionary 'antisense' technology, meant to work at the genetic level to block production of disease-causing proteins.

Diamond, whose company is developing antisense drugs for multiple sclerosis and psoriasis under license from Isis, said that the results probably reflected the nature of the disease rather than the difficulties of working with antisense technology.

"I think people put too much emphasis on this particular study as being a watershed for antisense," he said. "People should see it as what it is - it's not uncommon for drugs to fail at this stage."

Diamond said that while Affinitak did not satisfy the primary endpoint of survival, evidence showed that those who lived long enough to take the full course of chemotherapy did better, and noted that the antisense treatment might show a cumulative benefit over time. The study's patient group was difficult to treat due to the advanced stage of their disease, he said, with a much reduced group of patients surviving to take the full six-month course.

And Diamond said the Isis results would have no impact on the upcoming trials planned by Antisense. The company has recently been granted approval to begin a Phase I safety study for its multiple sclerosis treatment, and pre-clinical studies on the company's topical psoriasis treatment are also progressing.

"From our perspective it is not going to have any effect on our plans," he said. The risk profiles for multiple sclerosis and psoriasis were very different to that presented by cancer, he noted, and efficacy of the treatments had been shown in animal models.

"We're hopeful that investors will appreciate that," Diamond said.

Some US analysts said the real cause of the failure of the Isis trial could have be the target of the drug's activity, in this case a protein known as PKC-alpha. Related proteins may also have to be neutralised for such a therapy to work, they said.

"I don't think the trial failed because of the antisense technology but because inhibiting the PKC-alpha target didn't work," said analyst David Bouchey at CE Unterberg, Towbin.

Isis chairman and chief executive Stanley Crooke, who has spearheaded antisense research in the face of skepticism from many scientists, refused to be daunted. "We've had a disappointing trial here. But if we look at all the data, we are absolutely convinced that antisense technology works," he told Reuters last week.

Antisense's share price (ASX: ANP) has remained stable, closing on Friday at $AUD0.06.

-- Additional reporting by Reuters