Canadian cohort shows viral suppression most likely with atazanavir/ritonavir-based HIV treatment after 6 months

Atazanavir/ritonavir strongest among people with a history of injecting drug use

Antiretroviral therapy based on the ritonavir-boosted protease inhibitor atazanavir (Reyataz) was more likely to achieve virological suppression after six months than treatment containing the non-nucleoside reverse transcriptase inhibitor (NNRTI) efavirenz (Sustiva, also in the combination pill Atripla) among people with HIV starting treatment in the Canadian province of British Columbia, investigators report in the online edition of AIDS.

The study also showed that people with a history of injecting drug use (IDU) could achieve good virological outcomes at month six, most especially with regimens containing atazanavir.

“This observational study has shown that individuals, regardless of having or not a history of IDU, had better virologic outcomes if they initiated atazanavir/ritonavir-based HAART [highly active antiretroviral therapy] than those who initiated on efavirenz,” comment the investigators. They suggest that their findings should be tested in further research and that atazanavir/ritonavir may be an especially valuable first-line option for individuals with potential adherence issues.

Clinical trials investigating the safety and efficacy of antiretroviral drugs routinely exclude people who inject drugs. This is because of concerns that injecting drug users will not achieve the high levels of adherence needed to achieve and sustain virologic suppression. However, studies examining the virologic effectiveness of first-line HIV therapy for injecting drug users have produced conflicting results and optimum treatment strategies for this population have yet to be established.

Canadian investigators therefore compared six-month outcomes in 1163 individuals starting HIV therapy for the first time between 2000 and 2009. The investigators compared the chances of achieving a viral load below 50 copies/ml at month six according to history of injecting drug use and according to whether their therapy was based on atazanavir/ritonavir or efavirenz.The analysis employed was intention-to-treat: in other words, viral suppression at month 6 was analysed according to the starting regimen, regardless of any switches due to poor toleration of the initial treatment.

Individuals with a history of injecting drug use were more likely than those without a history of this behaviour to be female (p < 0.0001) and to have adherence below the optimum level of 95% (p < 0.0001). Their baseline CD4 cell count was also lower (170 vs 200 cells/mm³; p < 0.0001).

Type of HIV therapy did not differ by drug use status.

Six months after starting treatment, 68% of patients had a viral load below 50 copies/ml. This included 68% of patients who did not inject drugs and 32% of individuals with history of injecting drugs.

For individuals with no history of injecting drug use, a regimen based on atazanavir/ritonavir was approximately 50% more likely to achieve virologic suppression than an efavirenz-containing regimen (OR = 1.51; 95% CI, 1.04-2.18).

Therapy with atazanavir/ritonavir was almost twice as likely to suppress viral load than treatment with efavirenz for those with a history of injecting drug use (OR = 1.95; 95% CI, 1.25-3.04).

“Among IDUs…efavirenz-based HAART was associated with inferior short-term outcomes,” write the authors. They believe their findings could have important implications for the choice of first-line therapy for drug users and the use of HIV treatment as prevention.

“The higher barrier to resistance posed by…atazanavir/ritonavir, offers an advantage in a setting where less than perfect adherence may be more frequent. Given the increased recognition of the added secondary preventative value of HAART in decreasing the rate of HIV transmission, these findings are also of potential relevance for the roll out of ‘Treatment as Prevention” strategies.”