Saquinavir soft-gel capsule: An updated review of its use in the management of HIV infection

Saquinavir is a potent and highly selective HIV protease inhibitor. Initially formulated as a hard-gel capsule (HGC), saquinavir was the first protease inhibitor available commercially for the treatment of patients with HIV infection. The limited oral bioavailability of saquinavir HGC has been improved significantly with the introduction of a soft-gel capsule (SGC) formulation. Saquinavir SGC displays greater than dose-proportional pharmacokinetics and mean area under the plasma concentration-time curve (AUC) values are 8- to 10-fold higher with saquinavir SGC 1200mg 3 times daily than with the HGC formulation 600mg 3 times daily, the recommended dosages of the 2 formulations. In combination with other protease inhibitors (particularly 'low dose' ritonavir), the oral bioavailability of saquinavir (as either the HGC or SGC formulation) is markedly increased, allowing for reduced dosing frequency and/or dosage. The efficacy and tolerability of once- or twice-daily saquinavir SGC/'low dose' ritonavir combinations are currently being evaluated in patients with HIV infection. Data (up to 48 weeks) from noncomparative and comparative clinical trials evaluating saquinavir SGC-containing combination regimens in adult patients with HIV infection, support and strengthen the clinical efficacy profile of the drug that was demonstrated in initial trials. In antiretroviral therapy-naive and - experienced patients, saquinavir SGC combined with ≥2 nucleoside reverse transcriptase inhibitors (NRTIs), or nelfinavir, or nelfinavir plus 2 NRTIs or non-nucleoside reverse transcriptase inhibitors (NNRTIs), markedly improved immunological and virological surrogate markers (increased mean CD4+ cell counts and decreased mean plasma HIV RNA levels) of HIV infection. Saquinavir SGC demonstrated a trend to greater antiviral efficacy (measured by improvements in surrogate markers) than the HGC formulation (not statistically significant); a significantly greater proportion of patients treated with saquinavir SGC had plasma HIV RNA levels <400 copies/ml than patients receiving the HGC formulation. In the first direct comparison of 2 protease inhibitors, saquinavir SGC plus 2 NRTIs demonstrated similar antiviral efficacy to indinavir plus 2 NRTIs in patients with HIV infection (almost all of whom were antiretroviral therapy-naive); at 24 weeks, a significantly greater increase in CD4+cell count from baseline was obtained in the saquinavir SGC group compared with the indinavir group, although this difference was not apparent at week 32. Triple therapy with saquinavir SGC plus 2 NRTIs was as effective as nelfinavir-containing triple therapy, or quadruple therapy (saquinavir SGC plus 2 NRTIs plus nelfinavir) in markedly suppressing HIV RNA levels in antiretroviral therapy-experienced or -naive patients. Saquinavir SGC is generally well tolerated. Gastrointestinal disturbances (generally nausea, diarrhoea, abdominal pain, vomiting and dyspepsia of moderate or greater intensity) are the most common adverse events associated with saquinavir SGC-containing therapy. In comparative trials, saquinavir SGC-containing therapy was as well tolerated as indinavir- and nelfinavir-containing therapy; although there were no statistical differences between treatment groups, the incidence of diarrhoea was lower in patients receiving saquinavir SGC compared with nelfinavir, saquinavir SGC plus nelfinavir (all combined with 2 NRTIs) or saquinavir SGC plus nelfinavir without additional therapy. Compared with the HGC formulation, saquinavir SGC appears to be associated with a higher overall incidence of adverse events. Conclusions: Clinical trial data have shown that as part of triple or quadruple combination therapy, saquinavir SGC is an effective and generally well tolerated protease inhibitor in antiretroviral therapy-naive or -experienced patients with HIV infection. All treatment guidelines include protease inhibitor-containing regimens as a first-line option, although tolerability, resistance, drug interactions and patient compliance/adherence issues remain a concern. There is little doubt that protease inhibitors such as saquinavir SGC currently play a significant role as part of antiretroviral combination therapy. Given the evidence gained to date, saquinavir SGC represents an important component of antiretroviral treatment strategies in the management of patients with HIV infection; in combination with 'low dose' ritonavir, once-daily saquinavir SGC has the potential to form the cornerstone of dual protease inhibitor therapy.