The controversy about whether use of abacavir (ABC) increases the risk for virologic failure in patients with a high viral load was given center stage in back-to-back lat

"The ACTG 5202 endpoints are unique, [and] the interim results are unexpected and inconsistent with earlier data," said Keith Pappa, MD, who presented GlaxoSmithKline's review of 6 recent trials of abacavir involving 2940 treatment-nave patients, using the ACTG 5202 endpoints. "The range of response is between 87% and 95%," and there was no significant difference by baseline viral load, he said.

Dr. Pappa focused on the HEAT trial, which included 688 patients in a 96-week comparison of the same nucleoside regimens as the ACTG study. At 48 and 96 weeks, stratifying patients by viral loads above and below HIV RNA levels of 100,000 copies/mL, there were no statistically significant differences between the groups in terms of suppressing HIV RNA to levels lower than 50 copies/mL. Nor were there significant differences in terms of adverse events.

Dr. Pappa concluded, "The ABC/3TC regimen demonstrates [that] robust results, irrespective of baseline viral loads," are safe and well tolerated.

University of North Carolina, Chapel Hill, researcher Joseph Eron, MD, took the company to task for insinuating that the ACTG study, as the outlier, was any less valid, saying, "that is a bit disingenuous."

The 6 studies the company presented showed ABC/3TC to be marginally better in patients with lower rather than higher viral loads, whereas the comparator drugs were the reverse. Dr. Eron asked, "If you did cumulative analysis across all 6 studies, would you see a significant difference" between the higher and lower viral load groups?

Dr. Pappa replied that it is difficult to combine trials that had different entry criteria and used different regimens. "What we have to look at is the consistency of response and the percentage point difference."

Cornell University researcher Roy Gulick, MD, raised the point of clinical trials being "generalizable to the patients we take care of." He asked about the sex and racial/ethnic breakdown of participants in the company trials and whether the researchers has conducted an analysis of the HEAT trial along those lines. The company has not done so., Dr. Pappa said.

Dr. Gulick later acknowledged to Medscape HIV/AIDS that as yet there is no analysis of the ACTG 5202 data by race or sex. Still, "It is remarkable that more than half of [the study participants] were people of color, and we have to generalize those results to the population we're serving," he said.

"Race and ethnicity may be a marker for other things," such as diabetes, hypertension, and higher body mass index. "Other studies have shown that black race may be correlated with not as good virologic responses," Dr. Gulick said.