Viragen's anti-cancer product, the anti-CD55 antibody, was found to significantly enhance the activity of Rituxan when both drugs were used together in a cell-based evaluation study. The anti-CD55 antibody is under an exclusive option from Cancer Research Technology (UK), and is being developed for the treatment of a broad range of solid tumours. These preliminary results indicate its potential in improving the efficacy of leading cancer therapies, the company announced here.

Previous laboratory studies confirmed that the anti-CD55 antibody binds to a specific target expressed on the surface of tumour cells and removes one of the tumour's most important protective mechanisms, thereby making cancer cells vulnerable to attack by the immune system or other anti-cancer products. In this in vitro study, the antibody was combined with Rituxan (Rituximab), a leading cancer medication with global sales of more than $1.5 billion in 2004 that is jointly marketed by Biogen Idec, Inc. and Genentech, Inc.

The results showed that the combination of the anti-CD55 antibody and Rituxan led to a significant increase in the destruction of cancer cells as compared to Rituxan alone. The study was conducted by researchers at Viragen (Scotland) Ltd.

Karen Jervis, Viragen's Director of Product Development, explained, "There is much published data suggesting that the efficacy of many therapeutic products, including monoclonal antibodies, may be limited by the presence of certain proteins on tumour surfaces that protect the tumour from attack by the immune system. One of these proteins is CD55, which is expressed on most tumour cells at far higher levels than on normal cells, and its function helps prevent the destruction of tumour cells. We have developed a unique anti-CD55 antibody that effectively removes this protective effect."

"We have previously demonstrated that the anti-CD55 antibody binds to the CD55 protein on the tumour cell's surface with great specificity and deactivates its defense," she said adding, "Our new results using the antibody in tandem with Rituxan are very encouraging as they demonstrate the synergistic effect of 'anti-CD55' when combined with a proven antibody in vitro. We believe this same beneficial effect may also be realized when we use the antibody with other cancer products, and we hope to yield similar results with other commercial anti-cancer agents."

The development of the antibody has been funded in part by an $833,000 grant awarded to Viragen (Scotland) Ltd. from the Scottish Government (Scottish Executive) in April 2004, and Viragen scientists continue to design and conduct preclinical studies in support of this program.

Rituxan, discovered by IDEC, is approved for sale in approximately 70 countries worldwide. Biogen-Idec co-promotes Rituxan in the US with Genentech, Inc.