Encouraging data for GSK's Lexiva

UK drug major GlaxoSmithKline presented encouraging data from a head-to-head study evaluating its drug Lexiva (fosamprenavir calcium) versus US drug major Bristol-Myers Squibb's protease inhibitor Reyataz (atazanavir) in an open-label, randomized study of 106 antiretroviral-naive patients. Findings from the ALERT study were presented at the 4th International AIDS Society Conference, held in Sydney, Australia. In the group receiving ritonavir-boosted Lexiva, 75% had viral load of less than 50 copies/mL and 79%had viral load under 400 copies/mL vs 83% (p=0.34) and 87% (p=0.30) of patients on ritonavir-boosted atazanavir, respectively.

Ritonavir inhibits the protease in the body that breaks down protease inhibitors like Lexiva that act on the HIV protease, thereby boosting the levels of these HIV protease inhibitors in the bloodstream and making them more effective in suppressing the pathogen. A separate study, also presented at the IAS meeting, showed Lexiva's favorable efficacy and impact on lipids with a lower dose of ritonavir - 100mg instead of 200mg once daily, in treatment-naive patients, GSK stated. 84% of subjects in the ritonavir 100mg arm of the 115-patient study compared with 67% of those in the 200mg cohort achieved HIV RNA of less than 400 copies/mL at week 48 (p=0.026). Fat changes in the upper limbs for patients treated with Lexiva/r 200mg (n=43) vs Lexiva/r 100mg (n=44) was 16% vs 11% lower limbs (14% vs 9%) and trunk (32% vs 18%).

Lexiva is indicated in combination with other antiretrovirals for the treatment of HIV infections and is usually boosted with 200mg of ritonavir. A regimen of Lexiva with a 100mg dose of ritonavir is not approved, although it is currently being evaluated for use by the US Food and Drug Administration, GSK noted.