Cost Effectiveness of Lopinavir/Ritonavir Compared with Atazanavir??plus Ritonavir in Antiretroviral-Experienced Patients in??the US

Abstract

To estimate the cost effectiveness and long-term combined effects of HIV disease and antiretroviral (ARV) therapy-related risk for coronary heart disease (CHD) on quality-adjusted survival and healthcare costs for ARV-experienced patients. A previously validated Markov model was updated and supplemented with the Framingham CHD risk equation. The representative patient in the model was male, aged 37 years and had a baseline 10-year CHD risk of 4.6%. Patients started with either lopinavir/ritonavir (LPV/r) or ritonavir-boosted atazanavir (ATV+RTV) as the protease inhibitor (PI). The proportions of patients with viral suppression below 400 and 50 copies/mL, respectively, at week 48 reported in clinical trials were used to estimate the differences between these two therapies. The daily ARV costs were $US 24.60 for LPV/r capsules (2005 costs) and $US 26.54 for LPV/r tablets (2006 costs), $US 29.76 for ATV and $US 8.57 for ritonavir (2005 costs). Costs of other ARV drugs were taken from average wholesale drug reports for 2005. The cost of AIDS events was estimated from Medicaid billing databases and reflected a medical care system perspective and 2005 treatment costs. Cost-effectiveness calculations assumed a lifetime time horizon. The effects of different model assumptions were tested in a multiway sensitivity analysis by combining extreme values of parameters. The model estimated a clinical and economic advantage to using LPV/r over ATV+RTV, which varied depending upon the use of LPV/r capsules or tablets. Using LPV/r capsules was comparatively beneficial for ARV-experienced patients in quality-adjusted life-months (QALMs) of 4.6 (corrected for differences in CHD risk) compared with ATV+RTV. In addition, there were 5- and 10-year overall per-patient cost savings of $US 17,995 and $US 21,298, respectively. Estimates for the LPV/r tablet formulation approved in 2005 (assuming similar efficacy) improved cost savings over 5- and 10-year periods to $US 19,598 and $US 23,126 per patient, respectively, because of a drug price differential. Sensitivity analysis tested numerous assumptions about the model cost and efficacy parameters and found that the results were robust to most changes. Model limitations were the uncertainty associated with the model parameters used. LPV/r appears to be a highly cost-effective regimen relative to ATV+RTV for the treatment of HIV. The long-term CHD risk associated with LPV/r was minimal compared with the increased risk of AIDS/death and costs projected for a less efficacious PI-based regimen.