Budget Impact Analysis of Switching to Darunavir/Ritonavir Monotherapy for HIV-Infected People in Spain

Article excerpt

In an article from a previous issue of this journal, the potential economic impact of using darunavir/ritonavir (DRV/r) as monotherapy for treatment of HIV-1 infection was estimated, using UK prices.[1] In this analysis, we have adapted the scenario to Spain, a country with a larger HIV epidemic and a different system of HIV drug pricing. In addition, we have used updated 3-year results from the MONET trial[2] (MONotherapy in Europe with TMC114) as a basis for the analysis.

In Spain, 120 000-150 000 people are estimated to be infected with HIV, of whom 65 000 are currently receiving antiretrovirals.[3] Given the current economic crisis, there are pressures to lower costs in the Spanish National Health System across a wide range of conditions. In addition, new treatment guidelines recommend starting antiretroviral treatment at higher CD4 counts.[4-6]

The normal clinical practice is to start treatment for HIV infection with three antiretrovirals - typically two nucleoside analogues plus either a ritonavir-boosted protease inhibitor (PI) or a non-nucleoside reverse-transcriptase inhibitor (NNRTI).[4-6] with the aim of long-term suppression of HIV RNA and no accumulation of HIV drug resistance. Two randomized clinical trials have evaluated a subsequent switch to DRV/r as monotherapy, compared with DRV/r plus two nucleoside analogues. These trials recruited patients with HIV RNA suppression below 50 copies/mL for at least 6 months on current treatment, with no history of virological failure.

In the MONET trial,[2] 256 patients with HIV RNA <50 copies/mL on current highly active antiretroviral therapy (HAART) for over 24 weeks (NNRTI based [43%] or PI based [57%]), switched to DRV/r 800/100 mg once daily, either as monotherapy (n = 127) or with two nucleoside reverse-transcriptase inhibitors (NRTIs).[n = 129]. In the switch included analysis, the rate of HIV RNA <50 copies/mL by week 144 was 86.1% versus 84.3% in the DRV/r monotherapy and triple therapy arm, respectively. A parallel French study with a similar design - MONOI[7] - showed consistent results after 96 weeks of treatment.

The use of DRV/r monotherapy is included as a switch option in European treatment guidelines, for patients with HIV RNA suppression and no history of virological failure.[5] The Spanish GESIDA (Grupo de Estudio de Sida) guidelines also include DRV/r as an option for simplification in patients with no history of virological failure and with symptoms of NRTI toxicity with nucleoside analogue treatment.[6]

Using Spanish published prices from March 2011,[8] the annual cost of antiretroviral treatment was calculated for each patient in the MONET trial, both before and during the trial. The antiretrovirals used at the screening visit were used to calculate the cost of treatment before the trial. The sum of all antiretrovirals used during the trial was used to calculate the cost of treatment during the trial. For example, if a patient used DRV/r monotherapy for 8 months, and then intensified with NRTIs, the total cost of these antiretrovirals was calculated.

For the budget impact analysis, we used an estimate of at least 65 000 people in Spain currently being treated for HIV infection.[3] Based on analysis of a Spanish cohort[9] we assumed that at least 15% of these patients (n = 9750) have stable HIV RNA levels below 50 copies/mL on current treatment, and no history of virological failure. These 9750 patients would therefore be eligible to switch to DRV/r monotherapy, according to the 2009 European HIV treatment guidelines.[5] We assumed that 50% of these patients would be currently receiving NNRTI-based HAART, and 50% taking PI-based HAART, based on a recent study.[9]

At the week 144 visit, the percentage of patients with HIV RNA suppressed below 50 copies/mL was 86.1% in the DRV/r monotherapy arm and 84.3% in the DRV/r + two NRTIs arm. This analysis included the data from patients who had switched off their randomized treatment, either because of adverse events or elevations in HIV RNA. …