The scientific community got a little excited about the potential of antisense therapies in the early 1990s, when there was a boom in research and the potential of the mechanism was first being realised.

Then RNA interference came along, with its army of short interfering RNAs stealing the headlines from its older brother. The antisense community has not gone away, however.

In fact, there is already one antisense drug on the market and more in late stage clinical trials. Antisense is 10 years ahead of siRNA-based therapeutics, if not more.

The drug on the market is Vitravene (fomivirsen), a therapy for retinitis caused by HIV-related cytomegalovirus infection. It was approved by the FDA way back in 1998, and is a validation of the technology for its maker, California-based Isis Pharmaceuticals, because it was the world’s first antisense therapy to be approved for clinical use.

More is on the way, with Isis recently signing a licensing deal with Genzyme for its second-generation, cholesterol-lowering antisense drug mipomersen.

Isis is probably the world’s leading antisense pharmaceutical company, with 18 drugs in development. It also has a number of partner biotech companies around the world that assist the company to develop drugs for certain indications.

One of those partner companies is Melbourne’s Antisense Therapeutics, which this year signed a significant agreement with Teva Pharmaceutical Industries, the Israeli pharma that is now in the world’s top 20 and is best known for its Copaxone, a non-interferon therapy for the treatment of relapsing-remitting multiple sclerosis, with global annual sales in excess of US$1billion.

The deal that Antisense has signed with Teva also involves MS and is an antisense therapy known at the moment as ATL/TV1102. The drug was first in-licensed by Antisense from Isis, and the deal now involves on-licensing the drug to Teva for further development into Phase III.

The Teva deal is a boost to Antisense, with up-front fees and milestone entitlements amounting to $6m for the year to 30 June 2008, and there is the potential for milestone payments of up to $100 million, contingent upon successful commercialisation. Isis receives part of these payments under the original licensing deal.

The Teva deal is validation of both the technology and Antisense Therapeutics’ strategy, Antisense’s research director, Dr Christopher Wraight, says. The company’s strategy, with its first drug at least, is to license in interesting prospects from the likes of Isis, use the company’s knowledge of antisense technology, and to bring that to Phase I and Phase II clinical trials.

“We have just reported the successful completion of our Phase IIa trial in MS patients – a big achievement for an Australian company,” Wraight says.

“A lot of the development that has gone into the Antisense therapeutic platform has been done by Isis. They’ve taken the technology to the point where we can now inject antisense drugs subcutaneously – no other delivery formulation is required. We know where the drugs go, they are stable and they are specific.”