Prima subsidiary touts cancer antibody success

Prima Biomed (ASX:PRR) subsidiary Oncomab has published results of an animal study demonstrating the efficacy of its anti-Cripto monoclonal antibody in a mouse model of human colon cancer.

Cripto is a member of the EGF family of growth factors, due to its characteristic EGF-like domain, but its function is not well understood. It is primarily present in rapidly dividing tissue, and appears to play an important role in embryogenesis, but has minimal expression in normal tissues.

The antibody was shown to be effective at preventing new tumours from forming in the mice, and also slowed the growth of established tumours by up to 80 per cent. In vitro studies showed that the antibody inhibited cancer cell growth in a broad range of tumour types expressing Cripto, including colon, breast prostate, lung and leukaemia cancers, and the effect was enhanced in the presence of cytotoxic drugs including 5-fluorouracil, epirubicin and cisplatin.

The antibody appears to act by interfering with three cell signalling pathways, leading to an increase in apoptosis, or programmed cell death.

Now the company is moving the project into pre-clinical development, and is already in the process of humanising the antibody with its US partner Medarex.

"We hope to have identified our lead candidates by the end of this year, and then we have to adapt it for clinical use and perform the necessary pre-clinical studies," said business development manager Vanessa Waddell.

Waddell said that the relationship with Medarex meant that the company would follow the IND pathway for clinical trials, which would take longer than the equivalent Australian clinical trial approval process, and expected to be able to commence human trials by mid-2006.

Monoclonal antibodies already on the market as cancer therapeutics include Herceptin and Mabthera, which are used to treat breast cancer and lymphoma respectively. Waddell said that the anti-Cripto antibody had broader potential use as a cancer therapeutic as Cripto was present on more tumours.

Prima's share price rose on the news -- at the time of writing, shares were trading nearly six per cent higher at AUD$0.185.

The study was published in the June 1 issue of Cancer Research by scientists at the Austin Research Institute in Melbourne, who have licensed the antibodies to Oncomab for development.