Arthron arthritis candidate a stayer

Melbourne biotechnology company Prima Biomed (ASX:PRR) is chuffed with an intriguing result reported by its subsidiary Arthron from trials of its experimental rheumatoid arthritis drugs in mice.

Arthron reported today that its compounds appear to deliver a more prolonged therapeutic benefit in arthritic mice than currently used anti-arthritics like methotrexate.

Arthron researchers gave mice two collagen injections at 20 and 21 days, which would normally induce the same chronic inflammatory process that leads to rheumatoid arthritis in humans.

Over the next 10 days, the mice were treated either with methotrexate, or one of Arthron's experimental compounds. The treatments were then withdrawn.

Vanessa Waddel, Prima's business development manager, said the mice on methotrexate began to develop rheumatoid arthritis symptoms from day 35 onwards. But mice treated with the Arthron compound were still free of inflammation at 60 days.

Methotrexate suppresses inflammation by suppressing antibody-secreting B-cells; Arthron's experimental drug -- synthesised by its own chemists -- targets the Fc receptor, a cell-surface molecule that triggers the inflammatory process.

After methotrexate is withdrawn, B-cells begin to activate and secret antibodies that erode the soft tissues of the joints.

Because Arthron's molecule intervenes in the inflammatory process at an earlier stage, before B-cells begin targeting collagen antigens, the company believes it is likely to avoid some of the side-effects of current treatments for rheumatoid arthritis, including monoclonal antibodies.

Waddell said the persistence of the therapeutic effect in mice treated with the Arthron molecule was unexplained, and would be the subject of further research.

She described the new compounds as "template" molecules that needed further chemistry to optimise their half-life and potency.

The company is now seeking a partnering deal with a major pharmaceutical company to develop the compounds for human trials, possibly within in 12-18 months.

Waddell said Prima has decided to seek a partner at a relatively early stage in the drug's development curve because of the proliferation of novel therapies or rheumatoid arthritis.

"We have a very strong intellectual property position on the Fc receptor, and we want to be competitive with our approach. We think it's a very good target, but we're looking for some muscle to drive it forward against the competition," she said.

She says Arthron's Fc receptor strategy was generating considerable interest internationally, partly because a synthetic molecule would be cheaper to produce and simpler to use than biologics like monoclonal antibodies.