July 10, 2001
Dr. Pedro Cahn of Buenos Aires previously presented preliminary 24-week data from this study last year. Dr Vibhagool of Bangkok presented the final 48-week follow-up data of this multinational study. This study is an open-label study (not blinded or placebo controlled) comparing abacavir and combivir (ABC/COM) with indinavir and combivir (IDV/COM).
The advantage of the ABC/COM regimen is simplicity and convenience: two pills twice a day. With the approval of Trizivir in the U.S. and elsewhere last year, this regimen can be given as one pill twice a day. Adherence to antiretroviral therapy is one of the major factors -- if not the major factor -- in the success of these regimens.
Nearly perfect adherence has been shown to be necessary to achieve and maintain viral suppression with antiretroviral regimens. Adherence is favorably influenced by simplicity, convenience and reduced pill counts. The major pivotal published trial of ABC/COM (CNA3005) showed treatment response equivalence between this regimen and IDV/COM except in individuals whose baseline viral loads were >100,000. This led many to consider this regimen as inappropriate for those in that category. However, the 3005 study was placebo-controlled and double blinded which diluted the advantage of ABC/COM. Every participant had to take either abacavir or indinavir placebo tablets and follow the full fluid requirements and food restrictions of indinavir. Thus much of the adherence advantage of ABC/COM may have been lost. The preliminary 24-week data from the 3014 study already demonstrated that ABC/COM performed as well as IDV/COM. Now the final 48-week data confirm this. The study enrolled 342 individuals of whom more than a third had baseline viral loads over 100,000.
ABC/COM performed as well (if not better) than IDV/COM in terms of viral suppression (at <400 and <50 copy levels) and CD4 response in the total group as well as the subset with the higher viral loads. Fewer participants discontinued therapy due to adverse effects in the ABC group than the IDV group. The time to treatment failure was longer in the ABC group as well. The authors also evaluated adherence with a self-report questionnaire. Though this is not the gold-standard in measuring adherence (indeed there is no absolute gold standard), it has substantial validity and demonstrated statistically significant greater adherence to the ABC/COM regimen.
So what does it mean? This study confirms the usefulness of a very simple and convenient HAART regimen: abacavir with combivir, which in the form of trizivir is only two pills daily. The study also addresses and answers some of the concerns of using this regimen in individuals with high (>100,000) initial viral loads. And finally the study confirms what we already suspected: adherence will improve if we can make the regimens simpler.
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