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Small Molecule Inhibitor of the Protease Enzyme Cathepsin S

July 03, 2002

Medivir and Peptimmune jointly announced that an orally active, small molecule inhibitor of the protease enzyme Cathepsin S suppresses the development of chronic relapsing experimental autoimmune encephalomyelitis (CR EAE) in an animal model of the human autoimmune disease, multiple sclerosis (MS).

Oral dosing of the inhibitor in mice reduced both the severity and incidence of the neurological symptoms of CR EAE without any apparent signs of toxicity. This independent study at the William Harvey Research Institute, St. Bartholomew's and Royal London School of Medicine and Dentistry demonstrates a promising use for small molecule protease inhibitors in the treatment of MS.

The results build on previously reported data from an animal model of rheumatoid arthritis (RA), suggesting that an inhibitor of Cathepsin S offers a novel approach to the treatment of both MS and RA.

Currently approved drugs help to ameliorate the symptoms of MS and RA rather than halting the autoimmune reaction that is the underlying cause of the disease. For both MS and RA there is a large unmet medical need for new treatments that can stop the progression of these debilitating diseases.

Cathepsin S is a protease (protein degrading enzyme) that plays a significant role in the activation of certain immune responses. Previous in vitro studies have shown that inhibitors of Cathepsin S prevent or reduce activation of T helper cells. Results from this and previously reported studies demonstrate that Cathepsin S inhibitors can also prevent the activation of immune responses in vivo. Potential clinical applications of the inhibitors include controlling the initiation and/or progression of immune system disorders such as RA, MS, asthma, and organ/graft rejection.

Medivir and Peptimmune have a joint-venture program to develop Cathepsin S inhibitor drugs currently in the preclinical optimization phase. The program includes a license to the intellectual property rights to Cathepsin S as a therapeutic target from the Massachusetts Institute of Technology. Medivir/Peptimmune have also filed patent applications for a family of potent lead compounds against Cathepsin S. This article was prepared by Immunotherapy Weekly editors from staff and other reports.

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Submitted  8/27/2003 8:20:35 PM