Treatment with two antiretroviral drugs before exposure to HIV may significantly reduce the risk of acquiring the infection. Specifically, pre-exposure prophylactic (PrEP) regimen of tenofovir and emtricitabine has the potential to substantially reduce the lifetime risk of HIV transmission in high-risk populations, a new study indicates.

While the strategy is “unlikely to confer sufficient benefits to justify the current costs of tenofovir-emtricitabine,” the researchers say, it could become cost-effective if prices were lower or efficacy higher.

A multicenter team, led by Dr. David Paltiel of Yale School of Medicine in New Haven, Connecticut, performed a computer simulation of HIV transmission, detection and care to assess the efficacy and the cost of the PrEP regimen of tenofovir and emtricitabine among men who have sex with men and who are at high risk of HIV infection.

The average patient age as 34 years and high risk was defined as a 1.6 percent average annual incidence of HIV infection. The researchers defined acceptable PrEP efficacy as 50 percent. The monthly cost of the tenofovir-emtricitabine regimen was estimated to be $753.

“PrEP reduced lifetime HIV infection risk from 44 percent to 25 percent and increased average life expectancy from 39.9 to 40.7 years, Paltiel and colleagues report in the current issue of Clinical Infectious Diseases.

The average lifetime treatment costs increased from $81,100 to $232,700, the investigators estimate, “indicating an incremental cost-effectiveness ratio of $298,000 per quality-adjusted life-year gained.”

Still, Paltiel told Reuters Health, “We find that even small improvements in efficacy, pricing, and targeting to a younger, higher-risk population would make PrEP as cost-effective as many other widely accepted public health and medical interventions.”

He continued, “I don’t think anybody believes that PrEP is ready for prime time. We’re still in the research phase. But there are significant policy steps to be taken today.” These include making sure ongoing PrEP efficacy trials succeed, and planning what to do with the trial data.

Overall, Paltiel concluded, “In the face of the many recent disappointments PrEP shows promise as a strategy that could help contain the epidemic.”

SOURCE: Clinical Infectious Diseases, March 15, 2009.