Title: Reduction in Costs over two years when Treating with Darunavir/Ritonavir Compared to Atazanavir/Ritonavir in the UK
Abstract: Darunavir and atazanavir are currently the only protease inhibitors (PIs) recommended by the British HIV Association (BHIVA) treatment guidelines. The Office of AIDS Research Advisory Council (OARAC) reviewed the US HIV guidelines in April 2015 and delisted atazanavir/ritonavir (ATV/r) from the preferred PI options as a result of better tolerability (primarily due to discontinuations caused by adverse events (AEs)) of darunavir/ritonavir (DRV/r) compared to ATV/r based on findings from the ARDENT trial. The objective of this analysis was to quantify the economic impact of treating patients with DRV/r compared to ATV/r for two years in the UK based on drug costs, AEs and discontinuation due to AEs. A simple Markov model was built in MS Excel with two health states and 6-month cycles (4 cycles in total): on treatment with DRV/r or ATV/r and on subsequent treatment. All patients start on DRV/r or ATV/r and some discontinue and move to a subsequent therapy (weighted average of 3rd agents in treatment experienced patients, £11.10/day at list price). Discontinuation rates from ARDENT were converted to 6-month rates (4.60% for DRV/r and 8.78% for ATV/r) using the method from Miller et al. Patients were assumed to attend 6 further consultant appointments (£325/visit) in the first three months after switching as advised in the BHIVA guidelines for monitoring. AEs from ARDENT were also included. Using a list price of £10.57/day for DRV/r and £10.76/day for ATV/r), treatment with DRV/r saved £116 per patient in 6 months, £219 in one year and £393 over two years. Drivers of savings were the cost of consultant appointments and of subsequent treatment. Sensitivity analyses showed how DRV/r was cost saving even when the drug cost of DRV/r and ATV/r was assumed equal. In conclusion DRV/r has proven to be a highly tolerable and cost saving PI.