Peptech has high hopes for new antibody

Sydney peptide therapeutics developer Peptech (ASX:PTD) has taken delivery of its hot new anti-inflammatory domain antibody (dAb) from UK ally Domantis, and plans to begin human clinical trials in 2007.

Peptech R&D Director, Dr Phil Jennings said in vivo trials in a mouse model of rheumatoid arthritis, run by Domantis in Cambridge, indicated 'designer' domain antibodies' "clear potential" to become the next-generation successor to today's market-leading monoclonal antibody (mAb) therapies for inflammatory autoimmune diseases.

The cut-down antibody is designed to quench the biological flames lit by tumour necrosis factor-alpha (TNF-alpha), by binding to and neutralising the immune-system signalling molecule. TNF-alpha is a major cytokine involved in rheumatoid arthritis, inflammatory bowel (Crohn's) disease and other autoimmune diseases.

Centocor's rheumatoid arthritis therapy Remicade and Abbott's rival product Humira, along with Amgen's Enbrel, collectively racked up sales of US$6.4 billion last year, dominating the current US$9 billion (and growing) mAb therapeutics market.

Peptech's executive chairman Mel Bridges said the company, with its strong IP covering TNF-targeted antibody therapies, was in the fortunate position of receiving strong royalty streams from sales of both drugs.

Both Abbott and Centocor agreed to license Peptech's IP covering therapeutic antibodies that target the TNF-alpha molecule. Amgen's Enbrel for rheumatoid arthritis is not an antibody -- it uses a soluble form of the TNF-alpha receptor molecule to decoy the cytokine away from the membrane-bound receptor on immune system cells.

Domantis' proprietary dAb technology was developed as a potentially superior alternative to monoclonal antibodies -- it eliminates the bulky stem of the normal antibody molecule, leaving only the flexible, finger-like domains that mould to the shape of the target antigen.

Peptech's manager of investor relations, Dr Paul Schober, said dAbs were smaller, more stable, and potentially simpler to synthesise in cell culture systems.

Currently, Remicade as a rheumatoid-arthritis therapy costs up to $18,000 a year, although the drug is subsidised under the Pharmaceutical Benefits Scheme.

Peptech's Domantis-designed dAb could potentially be superior to both mAbs, more versatile and potentially, cheaper.

Domantis has used the mouse rheumatoid arthritis model to compare the performance of Peptech's new dAb against that of with that of current monoclonal antibody therapies.

The results were "exceptional", Jennings said. "The performance of the TNF dAb that has been transferred to Peptech to take into GMP (good manufacturing practice) production and into the clinic gives us confidence in our ability to commercialise this important drug lead," he said.

Domantis and Peptech reached an agreement in 2001 on development of dAb therapies after Peptech became the UK company's major shareholder -- it currently holds 36 per cent of Domantis' shares.

The TNF-alpha therapeutic is the first of other dAbs that Domantis will develop for the Sydney company. Schober said Peptech was still discussing potential targets with Domantis.

Schober said Peptech is continuing developmental research on the new molecule in Sydney. It is also talking to potential commercial suitors.

Abbott is also working with Domantis on dAb therapeutics.