In a letter sent Tuesday to health care providers around the country, drugmaker Gilead Sciences warns that an anti-HIV drug regimen that contains Videx EC (ddI) and Epivir (3TC), both manufactured by GlaxoSmithKline, and Gilead's medication Viread can result in poor virologic control and the development of drug-resistant virus. The letter says a study of the triple-drug regimen was halted because of a high rate of early virologic failure and the emergence of genetic mutations conveying resistance to nucleoside reverse transcriptase inhibitors. Based on the study results, Gilead does not recommend the use of Viread with ddI and 3TC for either patients newly starting antiretroviral therapy or for treatment-experienced patients. Patients currently taking that regimen should be considered for a change to a different drug cocktail, the company suggests.
The Gilead letter was prompted by clinical trial data showing a 91% virologic failure rate as observed by low reductions in HIV viral loads after 12 weeks of treatment. About 95% of trial participants had virus that developed a particular genetic mutation conveying drug resistance during the clinical trial, while the virus in about half the study volunteers developed two such genetic mutations. Other studies have shown similar results when evaluating triple-NRTI anti-HIV regimens. Studies of the Glaxo combination drug Trizivir, which contains AZT, 3TC, and Ziagen, and of a Ziagen-ddI-d4T combination also showed poor virologic response to the medications.