Clinical Trial of ViroLogic's PhenoSense HIV Demonstrates Benefits of Phenotypic Drug Resistance Testing Trial Also Uncovers Ways to Improve Interpretation of Drug Resistance Tests
SAN FRANCISCO, Jan 19, 2001 (BUSINESS WIRE) -- ViroLogic, Inc. (NASDAQ: VLGC) today announced preliminary results from a clinical trial of its PhenoSense(TM) HIV drug resistance test.
While the trial results showed no difference in the primary endpoints of the study, the trial uncovered significant new information that will improve the use of the assay in guiding patient therapy. In addition, when used to measure the number of sensitive drugs in an HIV patient's treatment regimen at baseline, PhenoSense HIV was a significant predictor of a patient's response to therapy. The trial also showed that the test provided a clinical benefit when used to direct therapy for key HIV patient populations, including those with extensive antiretroviral drug treatment history.
"Our findings demonstrate the benefits of phenotypic resistance testing for patients with extensive prior antiretroviral treatment history, as well as the ability of PhenoSense HIV to predict a patient's response to therapy," said lead investigator Dr. Richard Haubrich of the University of California, San Diego. "Overall, patients in the study had better outcomes than those in previous studies of resistance testing. Since increasing the number of phenotypically sensitive drugs in a treatment regimen improves suppression of HIV, I believe this study supports the continued use of phenotypic resistance testing to guide patient therapy. In addition, the preliminary analysis of the trial results indicate that resetting clinical cutoffs for NRTIs could improve the benefits of phenotypic testing."
In explaining the lack of difference in the primary endpoints, Dr. Haubrich indicated that a key finding of the study is that resistance to two nucleoside reverse transcriptase inhibitors (NRTIs), ddI and d4T, may be present at lower levels of susceptibility than previously recognized. Also, resistance to a third NRTI, abacavir, may have been present at higher levels than previously believed. Thus, patients in the PhenoSense arm of the trial may have been disproportionately treated with less effective drugs, masking the potential benefit of the test's utility in this study. To date, genotypic and phenotypic drug resistance tests have been limited in their ability to detect resistance to these drugs. This study for the first time provides clarification of appropriate clinical cutoff values for ddI and d4T.
The prospective study was conducted by researchers from the California Collaborative Treatment Group (CCTG) and ViroLogic. The trial, dubbed CCTG 575, was the longest prospective study of HIV drug resistance testing to date. Nine academic centers in the U.S. participated in the study. The study involved 238 patients, equally divided between those who received phenotypic drug resistance testing and those who did not. The researchers tracked the patients for 12 months. The data analysis evaluated the primary clinical endpoints: the average change in viral load from baseline to 12 months and the percentage of patients with undetectable viral load at 12 months.
The trial results demonstrated that the PhenoSense HIV drug resistance test was a significant predictor of patient response to therapy. Researchers found that the greater the number of sensitive drugs in a patient's initial regimen, the more likely a patient would have a substantial reduction in viral load. In addition, the study showed a clinical benefit from the use of PhenoSense HIV in selecting new treatment regimens for patients with five or more years treatment experience and those showing protease inhibitor resistance.
"The data from CCTG 575 add a great deal to our knowledge about drug resistance testing in HIV," said Dr. Douglas Richman, of the University of California, San Diego and the San Diego VA Healthcare System, and a senior investigator in the study. "The trial was quite remarkable in that both arms of the study reported much greater patient responses than have been seen in any of the previous prospective clinical studies of resistance testing."
New Clinical Cutoffs Established
ViroLogic is implementing appropriate changes in the clinical cutoff values for ddI and d4T based on the clinical study results. These new cutoffs will be used in PhenoSense HIV for samples sent to the ViroLogic clinical laboratory beginning next week. Clinically relevant cutoffs for another NRTI, abacavir, were introduced late last year, but were not in place during the study.
"We expect that the reassigning of clinical cutoff values for ddI and d4T will enhance the clinical application of PhenoSense HIV test results," said Dr. Nicholas Hellmann, ViroLogic's Vice President of Clinical Research. "Researchers and companies working on drug resistance have long had difficulty detecting resistance to ddI and d4T. We're pleased that the sensitivity of PhenoSense HIV has allowed us to identify more accurate cutoffs for these useful drugs."
"While the results of the trial were not statistically significant for the primary endpoint, we are encouraged by the amount of detailed data that the trial produced," said Bill Young, Chairman and CEO of ViroLogic. "We are also pleased that the study confirmed PhenoSense HIV's ability to successfully predict patient outcomes in some key patient populations. We now have a more sophisticated understanding of all of the trial variables and will continue to apply this knowledge to increase the effectiveness of the PhenoSense test."
About ViroLogic
ViroLogic is a biotechnology company developing and marketing innovative products to guide and improve treatment of viral diseases. The Company's proprietary technology, called PhenoSense(TM), tests for drug resistance and susceptibility in viruses that cause serious diseases such as AIDS, hepatitis B and hepatitis C.
ViroLogic's first product, PhenoSense HIV, is a test that directly and quantitatively measures resistance of a patient's HIV to antiviral drugs. The test results provide physicians with important information to help select appropriate drugs for their HIV patients. The Company is also developing PhenoSense products for other viral diseases and intends to use the results of its PhenoSense tests and other clinical data to develop its Therapy Guidance System(TM) (TGS(TM)), an interactive database to help physicians guide patient therapy. |
