The nucleotide analogue, tenofovir (Viread) appears to be as effective as the NRTI d4T (stavudine, Zerit) at suppressing viral load and boosting CD4 count when taken in combination with 3TC and efavirenz. In addition, tenofovir appears to cause similar levels of moderate to serious side effects as d4T.
Preliminary 48 week-study data from an ongoing three year double blind placebo controlled phase III clinical trial released by tenofovir manufacturer , Gilead, shows comparable efficacy between combinations containing tenofovir or d4T in previously untreated HIV-positive people. Data from the planned preliminary analysis must be released by the company as soon as it is completed in order to comply with US regulations designed to combat insider trading.
The safety and efficacy study is being conducted at 81 sites across the US and Europe and has enrolled 600 people, who have been randomised into two study arms to receive either tenofovir, 3TC and efavirenz or d4T, 3TC and efavirenz. At the start of the trial, the average viral load in the two groups approximately 90,000 copies/mL and average CD4 count was 279 cells/mm3.
After 48 weeks of treatment with either tenofovir, 3TC and efavirenz, or d4T, 3TC and efavirenz, an identical proportion of people in the two study arms, 87%, had achieved a fall in their viral load to below 400 copies/mL, and the proportion of patients experiencing a fall to below 50 copies/mL was almost identical, at 82% for the tenofovir arm and 81% for the d4T arm.
Similar increases in CD4 count were seen in the tenofovir and d4T groups, with an average increase of 169 cells/mm3 in the tenofovir arm and 167 cells/mm3 in the d4T group.
Overall, 9% of study participants withdrew because of side effects. Similar levels of moderately serious, or serious adverse effects were reported in the two study groups at 19% for those receiving tenofovir and 17% for the d4T arm. Moderately serious or serious lab abnormalities were seen in 28% of those receiving tenofovir and 31% of people receiving d4T.
It is expected that further data on side effects will be presented to the World AIDS Conference in Barcelona this July, and particular attention is likely to focus on levels of lipoatrophy reported between the two study arms, at 48 weeks and at the completion of the trial.
Gilead will now submit the data to regulatory authorities in Europe in order to gain a license for the use of tenofovir in first line therapy.