ViroLogic First to Report Clinically Derived HIV Drug Resistance Cutoffs Cutoff Data to be Provided in PhenoSense(TM) HIV Resistance Test Report, Will Improve Physicians' Ability to Guide Patient Therapy
SOUTH SAN FRANCISCO, Calif., Nov 16, 2000 (BW HealthWire) -- ViroLogic, Inc. (NASDAQ: VLGC) today announced that researchers have identified the first-ever clinically relevant HIV drug resistance cutoffs.
The clinical cutoff information will be incorporated into the Company's PhenoSense HIV resistance test report. This represents a major advance in the use of phenotypic resistance testing data to manage HIV patients and will improve physicians' ability to optimize patient therapy.
A clinical cutoff defines the maximum level of reduced drug susceptibility at which a patient still has a high probability of successful response to treatment with a particular drug. At resistance levels above the cutoff, patients are unlikely to respond to treatment. These cutoffs, developed by ViroLogic, were determined by using clinical trial data to evaluate the impact of changes in drug susceptibility on treatment outcomes.
"PhenoSense HIV is the first resistance test to provide clinically derived drug susceptibility cutoffs for HIV antiretrovirals," noted Dr. David D. Ho of the Aaron Diamond AIDS Research Center in New York. "This important achievement in the management of HIV drug resistance will provide doctors with more informed insight into the clinical significance of resistance test results."
For example, if an HIV drug demonstrates reduced clinical benefit when the virus becomes five times less susceptible to the drug than normal, then the clinical cutoff for that drug is 5-fold. Used in conjunction with a phenotypic drug resistance profile, which quantitatively measures resistance to each drug, cutoffs allow physicians to pinpoint, with greater precision than before, which drugs have reduced activity or are no longer working in a patient's treatment regimen.
Before today, it was difficult to know what level of reduced susceptibility corresponded to decreased treatment response or failure of a particular drug. Earlier phenotypic resistance tests employed cutoff values based on test sensitivity (e.g., 4-fold and 10-fold). Recently, these have been replaced with "biological" cutoffs based on the natural variability of HIV in untreated patients, but these also do not necessarily correlate with clinical response.
"We expect that a phenotypic resistance report incorporating clinical cutoffs for all antiretroviral drugs will become the standard in resistance testing," said Dr. Nicholas Hellmann, ViroLogic's Vice President of Clinical Research. "Today's announcement marks the first step toward that goal. By using these new cutoff values in our PhenoSense HIV report, we hope to further enhance the value and superiority of phenotypic resistance testing."
The new PhenoSense HIV report will include clinically relevant cutoffs for the recently approved drug lopinavir (Kaletra), produced by Abbott Laboratories, and abacavir (Ziagen), produced by Glaxo Wellcome. Reduced susceptibility to lopinavir becomes clinically significant at 10-fold, and reduced susceptibility to abacavir becomes clinically significant at 4.5-fold. Clinical cutoffs for the remaining HIV drugs will be added as additional clinical trial data become available. |
