Failure of Combination Abacavir + Tenofovir + Lamivudine (3TC)
In late July 2003 GlaxoSmithKline warned physicians that a three-drug combination of lamivudine (EpivirŽ), abacavir (ZiagenŽ) and tenofovir (Viread?) had failed to control HIV effectively in about half the treatment-naive patients in a clinical trial. The cause of the reduced response to this particular regimen is not known, but it may involve mutations causing cross-resistance to the drugs; Glaxo is also checking for chemical interactions inside the cell. The problem is not due to any one of the drugs; rather, for some reason this particular combination turned out not to work well.
The company advised:
"Abacavir and lamivudine in combination with tenofovir should not be used as a triple antiretroviral therapy when considering a new treatment regimen for naive or pre-treated patients;
"Any patient currently controlled on therapy with this combination should be closely monitored and considered for modification of therapy; and
"Any usage of this triple combination with other antiretroviral agents should be closely monitored for signs of treatment failure."
