Quad versus Atripla
Currently, there is only one option available for people who would like to take their entire antiretroviral (ARV) regimen in a single pill: Atripla. Two other all-in-one pills are following closely behind, however. One of those is Gilead’s Quad pill, which contains the company’s integrase inhibitor, elvitegravir, boosted by cobicistat, and paired with tenofovir and emtricitabine. Early news on the Quad pill from a phase II study—reported in early 2010 at the 17th Conference on Retroviruses and Opportunistic Infections (CROI) in San Francisco—was favorable.
At this year’s ICAAC, Richard Elion, MD, from the Whitman Walker Clinic in Washington, DC, presented 48-week data from the same study (Study 236-0104), which compared the Quad pill with Atripla in 71 people living with HIV who were starting ARV treatment for the first time. Forty-eight people were randomized to take the Quad pill, and 23 were randomized to take Atripla.
Elion’s team found that the Quad pill was similar in efficacy to Atripla. When he and his colleagues included people who dropped out of the study or discontinued treatment, 90 percent of those taking the Quad pill and 83 percent of those on Atripla achieved and maintained a viral load of less than 50 copies over 48 weeks.
When the team excluded the dropouts and discontinuations, 96 percent of those in the Quad arm had treatment success compared with 95 percent of those in the Atripla arm. Those taking the Quad pill had better CD4 responses than those on Atripla, with the Quad group seeing an average 240-cell increase, and those on Atripla seeing a 162-cell increase. There were a similar number of treatment discontinuations and side effects with both treatments.
Cobicistat versus Norvir
Just as Atripla is the only approved all-in-one regimen, Norvir (ritonavir) is the only approved drug to boost the blood levels of other ARVs, a process known as pharmacokinetic (PK) enhancement. Though Norvir, which is a protease inhibitor, was actually approved as an ARV, it is most commonly used now as a PK enhancer. Gilead is the first company to develop an alternative to Norvir for this purpose. That treatment, cobicistat, has no direct HIV activity. It was designed only as a PK enhancer.
Early data from a phase II study (Study 216-0105)—comparing cobicistat with Norvir—were reported earlier this year at CROI. In that study, 79 people were randomized to either cobicistat or Norvir, as a PK enhancer for the protease inhibitor Reyataz. People in both arms—50 who were randomized to take cobicistat and 29 who were randomized to take Norvir—also took Truvada (tenofovir plus emtricitabine).
At ICAAC, Elion presented 48-week data on this study. Elion’s team found that 84 percent of those in the cobicistat group achieved a viral load of less than 50 copies at 48 weeks compared with 86 percent of those in the Norvir group. When dropouts and discontinuations were excluded from the analysis, 91 percent of those on cobicistat and 96 percent of those on Norvir had an undetectable viral load at 48 weeks.
Discontinuation rates were similar between both groups. Overall, the most common side effects in both groups were diarrhea, nausea, fatigue and flatulence. Two people in the cobicistat arm had a more serious side effect, elevated bilirubin and rash. There were no serious side effects in those taking Norvir. CD4 cell increases were similar in both groups.