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Darunavir or Raltegravir in Rescue Regimen Raises Chance of Success 3 to 4 Times
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48th ICAAC
October 25-28, 2008
Washington, DC.
Mark Mascolini
A single-center study confirmed trial results showing a good chance of viral suppression with rescue regimens incorporating darunavir or raltegravir [1]. Among people starting either of these two drugs at the University of Alabama (UAB) clinic, two thirds reached a viral load below 50 copies after 24 weeks of treatment.
The findings are encouraging because they demonstrate that clinical trial results with these potent agents can be duplicated in the clinic. The results also buttress the validity of treatment guidelines that set a viral load below 50 copies as the goal of salvage therapy.
Michael Mugavero and UAB colleagues assessed virologic response in 109 people with triple-class experience in this prospective cohort study and excluded anyone in a clinical trial. The study group included 51 people taking darunavir, 33 taking another protease inhibitor (PI), and 25 not taking a PI. In those three groups, 35 (68.6%), 11 (33.3%), and 19 (76.0%) were taking raltegravir and 8 (15.7%), 0, and 10 (40.0%) were taking etravirine, the new nonnucleoside.
All cohort members started a rescue regimen after July 1, 2006 and had a viral load above 1000 when beginning their new regimen. Follow-up lasted through April 30, 2008. The group's age averaged 46 years, half were white, and most were men.
After 24 weeks on their new regimens, 65% taking darunavir had a viral load under 50 copies, compared with 48% taking another PI. Among people starting raltegravir, 65% had a 24-week viral load under 50 copies, compared with 38% not starting raltegravir. While 66% starting 3 or 4 active antiretrovirals (according to genotypic sensitivity score) reached a sub-50-copy load by 24 weeks, only 40.5% starting 1 or 2 active drugs reached that mark. (Twelve people had an unknown genotype.)
Multivariate analysis to sort out independent predictors of 24-week success considered baseline CD4 count, baseline viral load, PIs or raltegravir in the rescue regimen, age, race, gender, and insurance status. This analysis excluded use of enfuvirtide, maraviroc, or etravirine.
A higher baseline CD4 count had no impact of 24-week virologic response. Every 10-fold higher pretreatment viral load lowered the chance of success 36%, but this finding fell short of statistical significance (adjusted odds ratio [AOR] 0.64, 95% confidence interval [CI] 0.36 to 1.06)
Compared with people who had no PI in their rescue regimen, those starting darunavir/ritonavir had more than a 4 times better shot at a sub-50 load by week 24 (AOR 4.24, 95% CI 1.28 to 14.06). In contrast, regimens including atazanavir/ritonavir (in 18 people), lopinavir/ritonavir (in 11), fosamprenavir/ritonavir (in 2), nelfinavir (in 1), or atazanavir plus lopinavir/ritonavir (in 1) did not improve chances of virologic response compared with people who did not begin a new PI. Compared with people who did not start raltegravir, those who did tripled their chance of a reaching a sub-50 load by week 24 (AOR 3.1, 95% CI 1.12 to 8.62). Starting 3 or 4 active drugs, rather than 1 or 2, doubled the chance of 24-week virologic success (AOR 2.2, 95% CI 0.79 to 6.11).
The UAB team concluded that darunavir and raltegravir appear to work as well in the clinic as they did in trials and may be "ushering in a new era for treatment-experienced patients."
Reference
1. Mugavero M, Lin H, Willig J, et al. Impact of darunavir/ritonavir and
raltegravir in the clinic: a new era for treatment-experienced patients? 48th Annual International Conference on Antimicrobial Agents and Chemotherapy (ICAAC). October 25-28, 2008. Washington, DC. Abstract H-1262.
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