Clinical study shows VirtualPhenotype™ is superior to genotyping

First clinical study demonstrates that VirtualPhenotype™ is a reliable, independent predictor of clinical outcome

Results presented today at the 8th Conference on Retroviruses and Opportunistic Infections demonstrate, for the first time, the superiority of the VirtualPhenotype™ over conventional genotyping tests. The results showed that this unique resistance test developed by Virco can reliably and independently predict the way HIV patients will respond to therapy in a clinical trial. In the same analysis, conventional genotyping using rule-based interpretation failed to predict clinical outcome and a direct head-to-head comparison showed the superiority of the VirtualPhenotype™ to be statistically significant.

"This study is notable because it provides validation of the Virtual Phenotype with respect to virologic outcome in the context of a clinical trial," commented Scott Hammer, Chief of Infectious Diseases at Columbia University, New York. "This will reassure clinicians about using this approach to help manage their patients."

The study used data from VIRA 3001: the prospective randomised clinical trial that validated Virco’s Antivirogram® phenotype as a reliable predictor of treatment response. Patients’ samples were re-analyzed using the VirtualPhenotype™. This new test combines genetic information from the individual patient’s virus with the world’s largest database of resistance information from previous virus samples to produce a precise and reliable resistance score for each drug.

The study demonstrated that the VirtualPhenotype™ and Virco’s Antivirogram® phenotype are both statistically reliable, independent predictors of the patients' response to therapy in a stringent 'multivariate' statistical test. In contrast, a genotyping assay, which used conventional rules (developed by the international Resistance Collaborative Group) to interpret genetic information from the patients' virus, failed to predict outcome in the same analysis.

"These results show that the VirtualPhenotype™ can deliver a precise answer, without the doubts associated with genotyping," commented Dr. Brendan Larder, Chief Scientific Officer of Virco. "This is good news for physicians and their patients as they now have confirmation that the VirtualPhenotype™ is a reliable alternative to existing resistance tests that combines the speed and economy of genotyping with the reliability of phenotyping."

HIV genotyping involves reading the genetic code to detect where mutations have occurred that could confer resistance to one or more of the 15 HIV drugs currently available. The chief limitation of this approach is that there are over 100 mutations that can interact and counteract one another in highly complex ways to cause resistance, making the interpretation of raw genotypic resistance information extremely difficult. Interpretation has traditionally been attempted using mutation tables, rules or subjective methods to predict whether a virus will be sensitive or resistant to each drug.

Historically the only alternative to genotyping has been phenotyping where the virus is derived from the patient’s blood sample and grown in the presence of varying concentration of all the available drugs in the laboratory. This is more complex to perform and requires more time than genotyping.

Virco’s solution to this is a new, third approach to HIV drug resistance monitoring -- the VirtualPhenotype™. First the genetic code is read and all the resistance mutations detected. These data are then entered into Virco’s computerised system that searches the world’s largest database of approximately 100,000 genotypes and phenotypes for virus samples with the same patterns of mutations. Once these are found, the system retrieves the corresponding phenotypes for these samples (typically thousands per drug) and calculates the average resistance score for each drug. The VirtualPhenotype™ provides a quantitative estimate of resistance to each drug available.

Virco Background
Virco is a multinational biotechnology company with facilities in the United States, the United Kingdom, Belgium and Ireland. It applies the most advanced technologies in molecular biology, automation, ultra high-throughput screening and electronic data processing to the diagnosis and management of HIV, other infectious diseases and cancer. Virco is the only company to provide genotyping, phenotyping and the new, unique VirtualPhenotypefor testing HIV drug resistance. The Company’s Antivirogram® remains the only HIV phenotyping test that has been validated by a prospective controlled clinical trial as helping physicians select effective drugs and improve their patients’ clinical outcome. The Company believes it provides the most sophisticated and comprehensive portfolio of HIV drug resistance monitoring and decision support tools for physicians treating HIV infected patients.

Virco sells its testing services via Quest Diagnostics, Laboratory Corporation of America Holdings (LabCorp), SRL in Japan, as well as directly to HIV/AIDS centres in Europe, Canada, Australia and other countries around the world. Virco has a two-year agreement with Gilead Sciences for the promotion of Virco Resistance Monitoring Services to US HIV prescribers by the Gilead sales force. For further information, please visit Virco’s website: http://www.vircolab.com.

In January 2001, Virco and Tibotec announced that the two holding companies are going to merge.

Tibotec Background
Tibotec is an international group that has established a powerful and effective platform for rapidly discovering and developing superior drugs for unmet medical needs. Tibotec is developing novel anti-HIV drugs that address the serious problems of drug resistance, compliance and side effects. The Company also has a number of early stage research programs that are directed towards other diseases including cancer and tuberculosis. Tibotec was founded in 1994 and has over 150 staff worldwide. The Company has three sites: Mechelen, Belgium; Rockville, Maryland, USA and Dublin, Ireland.

For more information on Tibotec please see the website at http://www.tibotec.com

U.S. Peter Vigliarolo
Cooney Waters
212-886-2200
[email protected]