Dueling Data

With oil prices, presidential politics, and the Olympics having dominated the news this summer and fall, people may have not heard much about the International AIDS Conference, held in Mexico City in August. Here is the headline story: The controversy and confusion about the efficacy and safety of abacavir (Ziagen) that started at the retrovirus conference last winter only heated up in Mexico City. Presentation of the ongoing analysis of ACTG 5202 -- comparing abacavir to tenofovir (Viread) in combination with either efavirenz (Sustiva) or boosted atazanavir (Reyataz) -- continued to show abacavir-containing regimens failing more often than tenofovir-containing regimens in patients who have viral loads greater than 100,000. At the same time, the comparison of abacavir to tenofovir in combination with boosted lopinavir (Kaletra) in the HEAT study showed no difference. In addition, GlaxoSmithKline, the manufacturer of abacavir, reanalyzed six other abacavir studies and found no difference in virologic control with abacavir in patients with viral loads above or below 100,000. There was also continuing dueling data about the possible increased risk of cardiovascular events in patients taking abacavir compared to other nucleosides, first reported in the D:A:D study at the retrovirus conference. This time, data from the SMART study was examined. Again, those patients who were on abacavir had more cardiovascular events compared to those on other nucleosides as a whole -- but only if they already had multiple other cardiovascular risk factors. What was not presented was data on cardiovascular events specifically for those patients on tenofovir, the drug most likely to be used in place of abacavir. These data were published in the journal AIDS in September. Meanwhile, GSK reviewed 54 of its studies and found no increase in cardiovascular risk with abacavir. Now, in other news briefs: >Raltegravir (Isentress) has 96-week data comparing it to efavirenz and reports no new side effects or increased risk of malignancies. >Rilpivirine (TMC 278), the new once-a-day nonnucleoside reverse transcriptase inhibitor, continues to do well in Phase III trials. >Two new once-a-day NNRTIs with activity against resistant virus have completed Phase II trials with 1.8 log drops in viral load and good tolerability. They are moving toward Phase III trials. >Tenofovir now has seven-year follow-up data showing no significant impact on kidney function or bone mineral density. Limb fat increased by about 30%. >Tesamorelin (growth hormone releasing factor) at 26 weeks into its second Phase III trial showed about 10% decrease in abdominal fat without changing limb fat. It has been well-tolerated. Bowers is an HIV specialist and is board-certified in family medicine. He is in private practice in New York City.