Scottsdale, Arizona: According to two research groups, supervised treatment interruptions (STIs) in people taking 3TC-containing regimens, can result in the emergence of 3TC resistance. These data were presented at the Fifth Resistance Workshop in Arizona today.
The first study, from Bruce Walker’s lab at Massachusetts General Hospital and Havard Medical School, found the 3TC signature mutation M184V emerged during periods off therapy in one of fourteen people undergoing STIs after beginning anti-HIV therapy in acute infection. M184V was not detected in this person prior to treatment, nor when sequenced at day 3 of the first STI, but had emerged by day 21 (Tremblay).
A team from Badalona, Spain, similarly detected the 3TC mutation in two of twelve people participating in a study of STIs in chronically infected patients. M184V emerged at the end of the second and third STIs (Morales-Lopetegi).
Both groups hypothesise that 3TC’s long half-life may have been the cause of the problem. After stopping treatment, the drug remains at tapering levels in the blood for some time. These low levels create the right climate for selection of 3TC resistance mutations.
Tremblay C et al. HIV evolution during repeated supervised treatment interruptions following early antiretroviral treatment of acute infection. Antiviral Therapy 2001; 6(Supplement 1):17.
Morales-Lopetegi K et al. Selection of M184V mutation during repetitive cycles of structured antiretroviral treatment interruptions. Antiviral Therapy 2001; 6(Supplement 1):28.