OBJECTIVES: Darunavir (TMC114; DRV) is a novel protease inhibitor (PI) with demonstrated superior efficacy to currently available PIs for the treatment of human immunodefi ciency virus (HIV) infection in treatment-experienced adults who have failed prior antiretroviral therapy. We evaluated the cost-effectiveness of ritonavir-boosted DRV (DRV/r) plus an optimized background regimen (OBR) compared to currently available PIs plus OBR (control), from a Canadian provincial Ministry of Health perspective.
METHODS: A Markov model with 3-month cycles was developed to follow patients through six possible health states defined by CD4+ cell-count ranges. Costs (in 2006 Canadian dollars) were assumed to accrue based on estimates of health care services used during each health state. Each health state also had an associated utility value. Cost, utility, and mortality data were estimated from published Canadian sources. Transition probabilities were calculated from clinical trials. Both costs and outcomes were discounted at 5% per year. Two analyses were conducted: 1) incremental cost per additional person with viral load <50 copies/ mL at 48 weeks; 2) incremental lifetime cost per quality-adjusted life-year (QALY) gained. Extensive sensitivity analysis and variability (assessing the impact of practice patterns, population and model characteristics) analyses were performed.
RESULTS: In clinical trials, DRV/r is associated with a 36% absolute increase in probability of achieving viral load <50 copies/mL at 48 weeks and a gain of 1.27 QALYs over a lifetime. The incremental cost per additional person with viral load <50 copies/mL was $9,897; the incremental cost per QALY gained was $30,907. Sensitivity and variability analyses showed results were robust. For most of the credible uncertainty ranges, the cost-effectiveness ratio remained <$50,000 per QALY gained. Variability analyses showed cost-effectiveness ratios ranged from $23,283 to $34,135, depending most heavily on the assumed amount of tipranavir use in the model control arm and of enfuvirtide use in the OBR.
CONCLUSION: When compared to current standard of care, DRV/r plus OBR is cost effective in treatmentexperienced adults who have failed prior antiretroviral therapy.
