Date: Wed, 22 Sep 1999 17:31:28 -0700 From: Andrew Shih Subject: HIV Drug Resistance Studies in JAMA Use ViroLogic Technology For Immediate Release September 22, 1999 NEW STUDIES ON DRUG-RESISTANT HIV USE NOVEL TECHNOLOGY FROM VIROLOGIC, DEMONSTRATE ADVANTAGES OF PHENOTYPIC HIV DRUG RESISTANCE TESTING -- Results Published in the Journal of the American Medical Association -- SOUTH SAN FRANCISCO-Up to 28% of newly infected individuals may contract HIV that is resistant to one or more anti-AIDS drugs, according to two studies published today in the Journal of the American Medical Association. The studies were carried out by various medical research institutions in collaboration with scientists from ViroLogic, Inc. Drug susceptibility of HIV was measured with PhenoSense™ HIV, ViroLogic's novel, rapid phenotypic drug resistance assay. The studies indicated that phenotypic drug resistance testing could detect not only high-level HIV drug resistance, but also emerging drug resistance in newly infected patients. "While the transmission of drug-resistant virus raises new public health concerns, these studies also represent a great step forward in our understanding of HIV drug resistance," said William Young, incoming CEO of ViroLogic. "I am proud that ViroLogic was able to contribute both our expertise and technology, the PhenoSense HIV assay, to these important studies." High Prevalence of Drug-Resistant HIV Detected in Newly Infected Patients According to the reports published in JAMA, a significant portion of newly infected individuals was infected with HIV that is not sensitive to one or more AIDS drugs. -- A study led by Dr. Susan Little of the University of California, San Diego examined 141 newly infected individuals in five major metropolitan areas. The scientists concluded that 28% of those studied harbored HIV exhibiting reduced susceptibility to one or more AIDS drugs (the researchers defined reduced susceptibility as a greater than 2.5-fold decrease in susceptibility). -- A study led by Dr. Martin Markowitz of the Aaron Diamond AIDS Research Center in New York reached a similar conclusion. The researchers examined 67 newly infected individuals in New York and Los Angeles and found that 26.8% were infected with virus with reduced susceptibility to one or more drugs (reduced susceptibility was defined in this study as a greater than 3-fold decrease in susceptibility). Three patients, or 4.5%, exhibited a high level of resistance to multiple drugs. The study also noted an increase in transmission of drug-resistant virus in 1999, pointing to an upward trend in these cases. The results of these two studies suggest that HIV drug resistance testing may become a key component in designing effective HIV treatment regimens for newly infected patients. Phenotypic Testing Detects Wider Range of Drug Resistance The studies also revealed a marked difference in the reliability of phenotypic assays and the other widely available form of HIV drug resistance tests, genotypic assays. According to Dr. Little's study, while both assays were effective in detecting high-level drug resistance (a 10-fold or greater drop in susceptibility), genotypic testing, which attempts to predict resistance by examining the virus' genetic mutations, failed to identify lower-level changes in susceptibility. In Dr. Markowitz's study, genotypic testing identified drug-resistant virus in only 85% of cases determined to have reduced susceptibility by phenotypic testing. According to an accompanying editorial in JAMA, "Genotypic analyses remain somewhat problematic because mutations may be 'context dependent' and because the effects of natural polymorphisms on viral replication may differ based on other amino acid changes in a specific viral protein." On the other hand, the PhenoSense HIV assay, which directly challenges a patient's virus with each of the available anti-AIDS drugs, was able to detect minor changes in drug susceptibility that may also contribute to treatment failure. "The superiority of phenotypic testing in identifying various degrees of drug resistance may prove crucial in choosing the optimal drug combination for treatment of HIV infection," noted Dr. Nicholas Hellmann, Vice President of Clinical Research at ViroLogic. About PhenoSense HIV and ViroLogic PhenoSense HIV directly measures the sensitivity or resistance of a patient's virus to each of the currently available antiretroviral drugs for HIV, providing highly accurate, reproducible, individualized drug susceptibility information in two weeks, rather than the nearly 4-6 weeks for other currently available phenotypic resistance tests. The substantial advantage in turnaround time, sensitivity and reproducibility provided by PhenoSense HIV makes phenotypic HIV resistance testing a practical tool for physicians. ViroLogic, a privately held South San Francisco-based biotechnology company, is a leader in the development of novel therapy guidance tools to enable patients, physicians and medical reimbursers to make rational treatment decisions in the management of viral diseases and cancer. The company's proprietary technology is also being used in the fields of viral pharmacogenomics to identify, analyze and select new drug candidates for treating viral diseases and cancer, and in disease management through the development of therapy guidance algorithms to guide patient therapy. Contact: Sidney Ho, Director of Public Affairs (650) 635-1100, x206 sho@virologic.com ###