Study of Tests to Evaluate Effectiveness of Anti-HIV Drugs
The purpose of this study is to determine how laboratory tests called genotyping and phenotyping assess the effectiveness of antiretroviral drugs used to treat HIV infection. Some HIV-infected patients have measurable levels of virus in their blood even though they are taking combination drug therapy-including didanosine, stavudine, or efavirenz-against HIV. Genotyping and phenotyping can be used to test for resistance to a specific drug, thereby providing information that can help doctors decide on optimal drug treatment for a given patient. Genotyping identifies mutations, or changes, the virus undergoes that allow it to continue to grow despite drug treatment. Phenotyping involves growing the virus in test tubes with different amounts of drug and then calculating how much drug is required to stop its growth.
Patients 18 years of age and older with HIV infection and viral levels between 5000 and 100,000 copies per milliliter of blood who have been taking antiretroviral therapy for at least 6 months may be eligible for this study. Candidates will be screened with a urine test and various blood tests, including genotyping and phenotyping.
Participants will have a series of tests to determine whether or not a drug is active against HIV. This involves temporarily stopping the drug under study (i.e., either efavirenz or didanosine or stavudine). The study procedure is as follows:
- Patients will have six blood tests over 10 days to measure viral load while on all current anti-HIV medications. On one of those days two blood tests will be done to measure levels of didanosine or stavudine. Efavirenz will also be measured if this drug is to be stopped.
- The patient will temporarily stop the drug under while continuing to take the other drugs. (Efavirenz will be stopped for 3 weeks; stavudine and didanosine will be stopped for 2 weeks.) Seven blood tests will be done at the following intervals to measure viral load: For patients who stop efavirenz, blood will be drawn on days 13, 18, 20, 22, 24,28 and 30. (Day 0 is the first day of the study.) Patients who stop stavudine or didanosine will have blood drawn on days 11, 13, 15, 17, 19, 22 and 24. Repeat genotype and phenotype testing will also be done during this time, and a CD4 count (measurement of a certain type of white blood cell) will be done at the end of this 2- or 3-week period.
- The drug that was stopped will be restarted and viral load tests will be repeated. For pati...
|Official Title:||An Assessment of the Relationship Between Antiretroviral Drug Genotype/Phenotype (IC50) and Antiretroviral Activity in HIV-Infected, Drug-Experienced Patients With Suboptimal Suppression of Plasma Viral Load|
|Study Start Date:||November 2000|
|Estimated Study Completion Date:||September 2011|
The efficacy of highly active antiretroviral therapy (HAART) is limited by the emergence of drug-resistant virus strains. Development of resistance to one or more antiretroviral drugs in a HAART regimen may result in substantial rebound viremia and require a new drug regimen. The use of virus genotyping or phenotyping to identify drugs likely to be active in an anti-retroviral experienced patient is now recommended, but these tests have limitations and their clinical utility has not yet been established. The goal of this project is to investigate the correlation between phenotype/genotype to selected antiretroviral agents and short-term change in viral load upon discontinuation of a single antiretroviral agent from a failing regimen. For the nucleoside reverse transcriptase inhibitors (NRTIs) and the protease inhibitors, resistance is poorly understood; thus, we plan to determine whether a change in viral load occurs after discontinuing these drugs. If so, we plan to correlate those changes with phenotypic and genotypic characteristics. Study participants must have a stable viral load of at least 1000 copies/ml by bDNA assay despite HAART and must be receiving one of the anti-retroviral agents designated for study:. Baseline viral load will be established by multiple bDNA sampling over a 10-day period. Next, the drug of interest will be withdrawn and the rest of the regimen maintained for either a two week (NRTIs except 3TC, protease inhibitor) or four week (3TC) discontinuation to assess for change in viral load. Finally, the withdrawn agent will be re-instituted, and serial sampling for change in viral load, genotype or phenotype will follow.
|United States, Maryland|
|National Naval Medical Center|
|Bethesda, Maryland, United States, 20889|
|National Institutes of Health Clinical Center, 9000 Rockville Pike|
|Bethesda, Maryland, United States, 20892|