Predicting Direct Costs of HIV Care During the First Year of Darunavir-Based Highly Active Antiretroviral Therapy Using CD4 Cell Counts: Evidence from POWER

Background: Given the association between CD4 cell counts and HIV-related morbidity/mortality, new antiretroviral therapies could potentially lower the direct costs of HIV care by raising CD4 cell counts. Objectives: To predict the effects of the ritonavir-boosted, HIV protease inhibitor (PI) darunavir on the direct costs of care, while accounting for CD4 cell counts, during the first year of therapy in highly treatment-experienced, HIV-infected adults in different healthcare settings. Methods: The mean annual per-patient cost of darunavir/ritonavir (DRV/r) and control PI-based highly active antiretroviral therapy (HAART) was calculated from the proportional use of antiretroviral agents in the DRV/r and control PI arms of the pooled POWER 1 and 2 trials, applying drug-acquisition costs for five healthcare settings. Non-antiretroviral-related costs by CD4 cell count, derived from non-interventional studies in the same settings, were applied to the POWER data (proportion of patients with CD4 cell counts in different strata at week 48) to estimate mean annual non-antiretroviral-related costs per patient in patients receiving DRV/r or control PI-based HAART during year 1. Results: Across all settings, the mean annual per-patient cost of DRV/r-based treatment was 2-19% higher than that of control PI-based therapy during the first year of therapy. By raising CD4 cell counts, however, DRV/r-based regimens were predicted to lower mean annual non-antiretroviral-related costs by 16-38% compared with control PI-based therapy. When combined, the total annual per-patient cost of HIV care during the first year of therapy was estimated to be 7% lower in the DRV/r compared with the control PI arm using US data, 8% lower using Swedish data, budget neutral using UK and Belgian data and 5% higher using Italian data. Conclusions: Darunavir-based HAART may lower non-antiretroviral-related costs compared with control PI-based therapy in highly treatment-experienced, HIV-infected patients during the first year of therapy by improving patients' CD4 cell counts. These costs could partly/fully offset the increased acquisition cost of DRV/r in this patient population over the same period.