New drug-resistant HIV strain can escape detection

Mutations invisible to most assays cause resistance to two of the three classes of AIDS drugs

SCOTTSDALE, AZ, Wednesday, June 6, 2001 -- A new study presented today at the 5th International Workshop on HIV Resistance and Treatment Strategies shows that a mutation in the genetic code of HIV (the virus that causes AIDS) cannot be detected by most resistance tests and can cause high levels of resistance to one of the three classes of HIV drugs.

The new data show that a change at position 318 in the genetic code of HIV can make the virus highly resistant to treatment with the non-nucleoside reverse transcriptase inhibitors (NNRTIs). Since most HIV resistance tests cannot detect mutations located beyond position 300 in the genetic code, the findings are critical in demonstrating the ability of Tibotec-Virco�s tests to identify and detect all mutations known to be associated with drug resistance.

"These results show that this mutation, alone or in combination with others, can enable HIV to evade the effects of the NNRTIs," said John Mellors, MD, Professor of Medicine and Chief of Infectious Diseases, University of Pittsburgh, PA, and a member of the Organizing Committee of the Workshop. "The finding has important implications for physicians who use resistance testing in caring for HIV-infected patients."

Two years ago, Virco scientists discovered a mutation at position 333 that can cause dual resistance to AZT and 3TC - HIV drugs from another class. Taken together with today�s results, this means that resistance can develop to two of the three classes of drugs available and still escape detection by most resistance tests. Since HIV can only be treated effectively by combining drugs from two or all three of the available classes, resistance to drugs from one or two of these classes severely limits the options for effective treatment.

The study of several thousand HIV samples taken from clinical practices around the world over the last two years identified approximately 500 samples with the 318 mutation. Of these, up to 98% showed substantial resistance to the NNRTI drugs. The 318 mutation alone was found to be sufficient to confer high level resistance to delavirdine and in combination with other common mutations, increased substantially resistance to efavirenz.

"This finding emphasises the importance of continuing to study HIV resistance and of ensuring that our resistance testing technology keeps pace with the virus�s evolution," said presenting author Sharon Kemp, Director of HIV Research, Virco UK.

Background

Tibotec-Virco is a multinational biotechnology company with operating subsidiaries in the United States, Belgium, the United Kingdom, and Ireland. Tibotec-Virco sells its resistance testing services via Quest Diagnostics, Laboratory Corporation of America Holdings (LabCorp) and ARUP Laboratories in the USA, SRL in Japan, as well as directly to HIV/AIDS centres in Europe, Canada and Australia.

The Tibotec-Virco group was formed from the merger of Virco Group NV and Tibotec Group NV on March 14, 2001 and brings together the complementary expertise of Tibotec in drug discovery and development and that of Virco in pharmacogenomics and molecular diagnostics. Tibotec-Virco applies the latest techniques in pharmacogenomics, molecular biology, drug discovery and development, and artificial intelligence to develop individualised disease management products, services and technologies in HIV, other infectious diseases and cancer with the ultimate aim of enhancing and extending peoples� lives.

Tibotec-Virco is widely regarded as a world leader in HIV resistance testing and has developed some of the most widely available and trusted diagnostics in the world. The company has a number of genomics-based diagnostic tests under development for use in the management of hepatitis and cancer.

The current focus of the company�s drug discovery and development activities is the clinical development of a number of HIV/AIDS drugs that are active against strains of HIV that have developed drug resistance (a major and increasing cause of treatment failure).

For further information, please visit Tibotec-Virco�s website: http://www.tibotec-virco.com.

U.S.