31 Swarnali das 2007 disintegrins, angiogenesis, recombinant DNA technology, liposome, metastasis, suspended state of animation, cytostatic Contortrostatin (CN) (Mr 13,500 Da) is a novel homodimeric disintegrin isolated from the venom of Agkistrodon contortrix contortrix (Southern Copperhead) snake and displays two RGD motifs (one on each chain), which modulate its interaction with integrins on tumor cells and angiogenic vascular endothelial cells4. Angiogenesis is a process of the development of new blood vessels, which is exploited by a tumour to obtain a supply of nutrients and growth factors, a disposal route for its wastes, and a route for cancerous cells to spread.The copperhead protein acts by inhibiting the development of new blood vessels to nourish the tumours and by putting tumour cells into a "suspended state of animation",the dual action helped prevent the spread of cancer, a process called metastasis³. CN is cytostatic rather than cytotoxic. This means it does not kill tumour cells but "freezes" them in a long lasting state of "suspended animation". The cancer cells are prevented from adhering to and invading normal surrounding cells². Because the protein does not kill cells directly it has none of the side effects of powerful chemotherapy drugs, such as severe nausea². There are several approaches which are used or in trial to deliver CN efficiently in human body. CN administered in a liposomal formulation exhibits potent anti-angiogenic and tumor growth inhibitory activities in mice6. Liposome formulations used to deliver CN contain protein at concentrations greater than 1.5 mg/ml with encapsulation efficiency of greater than 80% as determined by BCA protein assay12. Mass production of contortrostatin using recombinant DNA technology is also in trial.