Cost effectiveness of lopinavir/ritonavir compared with atazanavir in antiretroviral-naive patients: modelling the combined effects of HIV and heart disease.

BACKGROUND AND
OBJECTIVE: The choice of initial highly active antiretroviral therapy (HAART) should take into account the need to balance efficacy, adverse event risk, resistance concerns for the treatment of HIV and treatment costs. Increased risk of coronary heart disease (CHD) may be of special concern in the selection of HAART therapy, because differences in potential CHD risk have been reported for different regimens. This study aimed to estimate the long-term combined effects of HIV disease and antiretroviral (ARV)-related risk for CHD on quality-adjusted survival and healthcare costs for ARV-naive patients.
METHODS: A previously validated Markov model was updated and supplemented with the Framingham CHD risk equation. In the model, the average patient was male, aged 37 years and had a baseline 10-year CHD risk of 4.6%. Patients started with either lopinavir/ritonavir or unboosted atazanavir as the first protease inhibitor (PI). Clinical trial data were used to estimate the differences between these two therapies. The daily PI costs were $US18.52 for lopinavir/ritonavir and $US22.08 for atazanavir. Other costs were estimated from Medicaid billing databases and average wholesale drug price reports. All model costs were reported as the 2004 present value in US currency. The model's time horizon reflected a patient's lifetime, and the perspective of the analysis was that of the healthcare system and did not include indirect costs in the model cost estimates. Various CHD risk levels were tested in the sensitivity analysis.
RESULTS: In the base case, the model predicted a median duration of initial PI regimen of 5.6 years for lopinavir/ritonavir and 3.8 years for atazanavir. Over 10 years, patients who started on atazanavir had 30 additional AIDS events per 100 patients. Only 0.7 additional CHD events per 100 patients occurred for those who started on lopinavir/ritonavir. The model estimated 10-year total healthcare cost savings of $US12,543 per patient in the lopinavir/ritonavir group. The lifetime incremental cost effectiveness of lopinavir/ritonavir versus atazanavir was $US6797 per quality-adjusted life-year gained.
CONCLUSION: Lopinavir/ritonavir is a highly cost-effective regimen relative to atazanavir for the treatment of HIV. The effect of lopinavir/ritonavir on long-term CHD risk was minimal compared with the increased risk of AIDS/death projected for a less efficacious first PI regimen. The cost of lipid-lowering drugs and treatment of CHD for patients taking the lopinavir/ritonavir regimen was only 1.2% of the cost of AIDS care per person, which was too small to have a significant effect on the overall cost savings with lopinavir/ritonavir therapy. Thus, a decision to forgo potency and durability in an ARV regimen for an ARV-naive patient in favour of a less potent regimen with an improved lipid profile may prove to be costly over time, in terms of both budget impact and life expectancy.