Viron reports positive proof of concept results in arthritis for its VT-346
anti-TNF therapeutic

LONDON, ON, March 16 /CNW/ - Viron Therapeutics Inc. announced that VT-346, an anti-TNF protein therapeutic, demonstrated positive results in a pivotal proof of concept study in the gold standard transgenic mouse model for arthritis. VT-346 achieved a statistically significant, dose dependent impact in this preclinical model of arthritis and prevented deterioration due to disease in terms of weight gain, arthritic score and pathology parameters. VT-346 had particularly strong protective effects on therapeutically-important bone and cartilage damage in this model. The target for VT-346 is the inflammatory cytokine TNF, which is also the target for several biological therapies whose annual sales are expected to top $20 billion in 2010, making anti-TNF therapies the most commercially successful single-target group of biological therapies. Notable, however, is VT-346's unique method of neutralizing TNF, an important mediator of inflammation and therapeutic target in diseases including rheumatoid arthritis, Alzheimer's disease and Crohn's disease.

"The development of an anti-TNF therapy that is fundamentally different from existing therapies offers hope to patients that do not respond adequately to existing anti-TNF drugs," said Dr. Edward Keystone, Head of the Rebecca MacDonald Centre for Arthritis and Autoimmune Diseases and a recognized leader in the development of drugs targeting rheumatoid arthritis. "Approximately 30-50% of patients do not respond optimally to currently available anti-TNF therapies. The potency in pre-clinical studies and unique mechanism by which VT-346 functions could allow clinicians to achieve better outcomes in these patients."

"VT-346 surprised us in pre-clinical studies when it demonstrated up to one hundred fold better inhibition of human TNF when compared to currently marketed therapies," said Dr. Mike Gresser, former Head of Inflammation and Neuroscience research at Amgen and consultant to Viron. "From this potent impact in primary human tissue, it seems VT-346 was doing something fundamentally different from existing anti-TNF products. More recent characterization of the molecule has provided some key insights into this distinct mechanism of action and allowed us to file some new patents. We are currently discussing this mechanism of action under strict confidentiality with interested partners."

"The results from our VT-346 program results continue to validate the ability of our PROSPECT(TM) platform for generating innovative and potent therapeutics," said James Rae, CEO of Viron. "In addition to the potential for VT-346 as an anti-TNF therapy, we have also filed new patents on the use of VT-346 to aid in the discovery of antibodies that mimic its unique mechanistic profile, making this program both a drug candidate and a potential platform for the identification of new and unique anti-TNF therapies."

Viron researchers selected this animal model of arthritis due to its accurate prediction of clinical benefits for the currently marketed anti-TNF therapeutics. These animal model results build on early pre-clinical in vitro testing and characterization of this compound that was conducted using human tissues to demonstrate potent anti-inflammatory activities. Studies were conducted by BioMedCode, a recognized leader in the use of this transgenic model.

VT-346 Background

VT-346 was discovered as a secreted protein produced by the Tanapox virus which infects primates and was first isolated in the Tana river valley of Kenya. Once identified, Viron generated a recombinant version of the molecule made in standard mammalian expression systems used in the development of numerous protein therapeutics.

About Viron Therapeutics Inc. (www.vironinc.com)

Viron Therapeutics is a biopharmaceutical company pioneering the development of viral proteins, a revolutionary new class of drugs. By harnessing the evolutionary power of viruses and other pathogens to evade the human body's protective inflammatory response, Viron is able to identify and develop powerful protein therapeutics that have distinct advantages in potency and efficacy over conventional drug therapy. The Company's proprietary PROSPECT(TM) technology, PROtein Screen for Pathogen-Evolved Combination Therapeutics, is a platform for the discovery of new immune-modulating protein therapeutics. Its significant pipeline of products target critical pathways that have broad application to immune and inflammatory-based diseases such as cardiovascular disease and rheumatoid arthritis. VT-111, the Company's lead compound, recently completed a successful Phase IIa study in patients receiving cardiovascular stents, and is also in development to treat solid organ transplant rejection, with the solid organ transplantation clinical program expected to begin in 2010.

For further information: Kevin Sullivan, Vice President, Business Development, Viron Therapeutics Inc., Phone: [phone], Fax: [phone], E-mail: [email protected], www.vironinc.com; Ross Marshall, Investor Relations, The Equicom Group Inc., Phone: [phone] (Ext. 238), Fax: [phone], E-mail: [email protected]