A HAART combination comprising abacavir, 3TC and efavirenz is just as effective as AZT, 3TC and efavirenz at suppressing HIV viral load, but is much better at boosting the immune system in treatment-naive individuals, according to data presented to the 43rd Interscience Conference on Antimicrobial Agents and Chemotherapy in Chicago on September 14th.
Investigators presented data from the CNA30024 study. This study was a 48 week double-blind, randomised multi-centre investigation, the primary purpose of which was to compare the virological potency of a regimen including abacavir, 3TC, and efavirenz, versus AZT, 3TC, and efavirenz. The AZT-containing regimen has already been shown to be an effective, safe and well tolerated combination for treatment-naive individuals, and is one of the initial HAART regimens recommended by the British HIV Association. However, some patients find AZT difficult to tolerate, and an abacavir-containing regimen may be better tolerated in the long-term amongst those who do not experience the initial hypersensitivity reaction.
Secondary end-points of the study included an evaluation of the regimens’ immunological effects, and a comparison of their safety and tolerability.
A total of 649 patients were recruited to the study. Median baseline viral load was 4.79 log10, with 39% of individuals having a viral load above 100,000 copies/mL. The median CD4 cell count was 264 cells/mm3.
By week 48, 70% of patients in the abacavir arm had achieved a viral load below 50 copies/mL compared to 69% of patients in the AZT arm. When the investigators compared the immunological effect of the two regimens, they established that the abacavir-treated patients gained an average of 209 cell/mm3 compared to 155 cells/mm3 in the AZT arm. This difference was significant (p=0.05). The investigators were surprised by the extent of the difference in CD4 cell gain between the two arms of the study, and further analysed these data, checking for CD4 - CD8 ratio and CD4 cell percentage. This further analysis did not change their findings.
The safety and tolerability of the two regimens were comparable, although 9% of patients were suspected to have experienced an abacavir hypersensitivity reaction. Even though rigorous checking reduced the incidence to 7% it is still significantly higher than the rate of 3%-5% seen in previous studies reported by GlaxoSmithKline. However, the investigators note that 3% of patients in the AZT arm were reported as experiencing a reaction to abacavir. They suggested that since a very cautious approach is taken to the side-effect by both doctors and patients, this possibly leads to the reaction being over-reported.
The investigators concluded that the two study regimens showed a comparable virological response, but that patients treated with abacavir showed a significantly better immunological response by the end of the study.
Further information on this website
Abacavir - key research - summary of key studies
Abacavir - overview - summary of use of abacavir in HIV treatment
Choosing a nucleoside analogue backbone - includes a discussion of previously reported evidence on the abacavir/3TC combination.
De Jesus E et al. Efficacy and safety of abacavir versus zidovudine in antiretrovrial therapy naive adults with HIV-1 infection (study CNA30024). 43rd ICAAC, abstract H-446, Chicago September 14 - 17th, 2003.