The three-in-one pill anti-HIV medication Trizivir has been approved for use in Europe, the European Medicines Agency announced yesterday. The drug is likely to be available on prescription by the end of November. Trizivir is a combination of the three nucleoside analogues AZT, 3TC and abacavir, and is a Glaxo-Wellcome product.
However, the agency's scientific committee, the CPMP, has warned that use of Trizivir needs special consideration in patients with viral load above 100,000 copies/ml, following the results of the CNAA3007 study which compared AZT, 3TC and abacavir to AZT, 3TC and indinavir. This study found that in the subset of individuals with viral load above 100,000 copies, the indinavir-containing arm performed better than the abacavir-containing arm. This finding has led to concerns that triple nucleoside therapy might not be suitable for people with high viral load.
At the Thirteenth International AIDS Conference last week in Durban, results from two further comparative studies were presented, suggesting that an abacavir-containing triple nucleoside regimen may be just as potent as a PI-containing regimen.
The French Ecureuil, or Squirrel, trial compared Combivir/abacavir with Combivir/nelfinavir three times daily, the standard dose at the time the trial was designed. Investigator Sophie Matheron offered no explanation for the name of the trial, presumably named to make it sound more cuddly, but did report that after 24 weeks of follow-up, there was no difference in the proportions of individuals in each arm with viral load below 50 copies (67% vs 66%: ITT: switch=failure). Ninety-eight patients have been recruited to the abacavir arm, and 97 to the nelfinavir arm. However, only 5.6% of those analysed had viral load above 100,000 copies/ml when they joined the study, because the protocol was not amended to admit people with high viral load until halfway through the study. This makes it impossible to judge whether abacavir is a potent substitute for a PI in people with high viral load, and more robust results are unlikely to be available until early next year. Four abacavir hypersensitivity reactions were reported.
CNAB3014 is an open label study conducted in Argentina that is comparing Combivir/abacavir with Combivir/indinavir (three times a day dosing). In this study, 36% of the 342 participants had viral load above 100,000 copies/ml at baseline. After 24 weeks on treatment, those with viral load above 100,000 copies/ml were just as likely to have viral load below 50 copies on abacavir as on indinavir (55% vs 54%) using an intention to treat: missing=failure analysis. There was no difference in the rate of adverse events leading to discontinuation, but grade 3 or 4 adverse events were more common in the indinavir arm (12% vs 4%). No specific information on the number of abacavir hypersensitivity reactions was presented.
References
Cahn P et al. Preliminary efficacy, adherence and satisfaction with COM/ABC versus COM/IDV, an open-label randomised comparative study (CNAB3014). XIII International AIDS Conference, Durban, abstract WeOrB606, 2000
Matheron S et al. An open label study to compare efficacy and safety of the triple nucleoside analog combination Combivir/abacavir versus a protease inhibitor containing regimen in antiretroviral naïve adults. CNAF3007/Ecureuil. XIII International AIDS Conference, Durban, abstract WeOrB605, 2000.