Cost of switching darunavir+ritonavir (DRV+RTV) to lopinavir/ritonavir (LPV/r) in HIV-1-infected treatment-na ve women of child-bearing age (WOCBA)

Guidelines consider LPV/r a preferred protease inhibitor for use during pregnancy. When an HIV-infected woman receiving DRV+RTV becomes pregnant, a switch to LPV/r may be warranted. The budget implications of proactively initiating LPV/r versus initiating DRV+RTV and then switching has not been examined. A cost-minimization analysis was performed from the US healthcare perspective for HIV-1-infected, treatment-na ve WOCBA comparing: initiating LPV/r in all patients versus initiating DRV+RTV and switching to LPV/r when pregnant. A discrete event simulation was employed to represent antiretroviral (ARV) therapy management. Healthcare utilization and clinical trial data [1] were used to model pregnancy rates [2], ARV regimen switch rates, and impact of treatment as a function of CD4-cell count and viral load, adherence, treatment response, acquired resistance mutations, and ensuing treatment changes. Five- and 10-year costs incurred due to ARV therapy, clinician visits and management of AIDS-related, non-AIDS related, and cardiovascular events were estimated. Base-case analysis assumptions: switching to LPV/r can occur only once at first pregnancy, 30% of WOBCA switch to LPV/r circa time of pregnancy, and women's adherence to medication improves by 15% when becoming pregnant. Sensitivity analyses varied the rate of switching to LPV/r at time of pregnancy, pregnancy rates, adherence improvement, and healthcare costs. Daily drug cost of LPV/r + TDF/FTC was $56.59 while DRV+RTV+TDF/FTC was $73.89. Costs were discounted at 3% per annum. Survival was similar in both groups. Five- and 10-year total healthcare costs of ARV-na ve HIV-positive WOCBA who initiate LPV/r were $108,200 and $192,600 per patient, respectively, compared to $132,200 and $234,400 when women initiated DRV+RTV and then 30% switched to LPV/r. Initiating with LPV/r resulted in 5- and 10-year savings of $24,000 and $41,800 per patient, respectively. If 100% of patients who initiated with DRV+RTV switched to LPV/r upon pregnancy, the savings per patient were $21,300 at 5 years or $33,140 at 10 years, since a greater number of patients switch to the less expensive LPV/r. Sensitivity analyses showed that initiating with LPV/r was always cost-saving relative to DRV+RTV. Initiating HIV-infected, treatment-na ve WOCBA on LPV/r was cost-saving compared to initiating DRV+RTV. Limitations of the analysis include the uncertainty of long-term outcomes projections driven by short-term clinical trial endpoints.