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Dolutegravir in Treatment-Experienced People Who Have Not Previously Used an Integrase Inhibitor

August 2013

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Researchers in Australia, Latin America, North America, Europe, South Africa and Taiwan recruited 715 HIV-positive people for a double-blind, placebo-controlled study comparing regimens containing dolutegravir to regimens containing raltegravir. All participants had previously used anti-HIV therapy (commonly called ART or HAART) and nearly half of participants had a history of AIDS. Moreover, according to researchers, nearly half of participants had HIV that was resistant to "at least one drug in each of three or more [classes of drugs]."

After one year, researchers found that, in general, a dolutegravir-containing regimen was statistically superior to a raltegravir-containing regimen. This finding was driven by virologic results with fewer dolutegravir users developing treatment failure.

The average profile of participants at the start of the study was as follows:

  • gender: 32% women, 68% men
  • age: 43 years
  • 70% of participants had a viral load of 50,000 copies or less
  • CD4+ count: 200 cells
  • history of AIDS: 46%
  • 79% had HIV that was significantly resistant to protease inhibitors or did not use the powerful protease inhibitor darunavir (Prezista)
  • HIV resistant to three or more classes of drugs: nearly 50%
  • duration of previous HIV therapy: 6 years
  • co-infection with hepatitis B virus (HBV): 5%
  • co-infection with hepatitis C virus (HCV): 11%
  • co-infection with both HBV and HCV: 1%

Researchers referred to the drugs used in addition to dolutegravir or raltegravir as the "background" regimens. Drugs commonly used as background regimens in this study were as follows:

  • darunavir (Prezista) + ritonavir (Norvir) + tenofovir (Viread)
  • lopinavir-ritonavir (Kaletra) + tenofovir
  • darunavir + ritonavir + etravirine (Intelence)
  • lopinavir-ritonavir
  • atazanavir (Reyataz) + ritonavir + tenofovir
  • darunavir + ritonavir + maraviroc (Celsentri)

Participants were randomly assigned to receive dolutegravir or raltegravir, so that their regimens were as follows:

  • dolutegravir + background regimen + placebo
  • raltegravir + background regimen + placebo

The double-blind, placebo-controlled part of the study lasted for 48 weeks. After this, participants who received dolutegravir and who completed the first 48 weeks of the study were told which drug they received. They were also offered continued treatment with dolutegravir and will be monitored every 12 weeks.

Results -- Changes in Viral load

In both study groups the proportion of participants with a viral load less than 50 copies/ml rose sharply during the first four weeks, then less so over the subsequent four weeks. After the eighth week of the study, the proportion of participants with a low viral load (less than 50 copies/ml) remained relatively stable. The swiftness of the initial decline in viral load is something that is associated with integrase inhibitors.

The proportion of participants with a viral load less than 50 copies/ml at the 48th week of the study was distributed as follows:

  • dolutegravir-based regimens: 71%
  • raltegravir-based regimens: 64%

Researchers performed calculations and concluded that dolutegravir's anti-HIV effect was "statistically superior" to that of raltegravir.

Why the Difference?

Both dolutegravir and raltegravir are good drugs when used as part of combination therapy. However, the finding of statistical superiority favouring dolutegravir arose according to the researchers because virologic failure "occurred earlier and more frequently in [participants who took raltegravir (12%) compared to participants who took dolutegravir (6%)]."

Furthermore, 42% of 45 participants who took raltegravir and who developed virologic failure were termed "non-responders" by researchers. Essentially, non-responders did not have a major decrease in viral load and were not able to have their viral load fall below the 400-copies/ml mark. This contrasts with only 10% of 21 participants who took dolutegravir and who developed virologic failure and who were also virologic non-responders.

Darunavir Plays a Role

Darunavir is a powerful protease inhibitor. When taken with a small dose of ritonavir, darunavir can be taken once daily. When researchers analysed the data from Sailing among participants who took darunavir-ritonavir with dolutegravir or raltegravir, dolutegravir's anti-HIV effect was found to be roughly equivalent in potency to raltegravir. However, bear in mind that the majority of participants did not use darunavir.

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This article was provided by Canadian AIDS Treatment Information Exchange. It is a part of the publication TreatmentUpdate. Visit CATIE's Web site to find out more about their activities, publications and services.

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