The results are from the KLEAN study, a randomized, open-label study of the safety and efficacy of Lexiva (fosamprenavir; 700mg twice daily), in combination with Norvir (ritonavir; 100mg twice daily), versus Kaletra (400mg lopinavir plus 100mg ritonavir twice daily). Patients also received once-daily Epzicom (a tablet containing 600mg abacavir and 300mg lamivudine). The study enrolled 887 HIV-positive patients beginning treatment for the first time and followed them on therapy for 48 weeks.

The press release indicates that 73% of patients in the Lexiva/Norvir group maintained viral loads below 400 copies/mL after 48 weeks, compared with 71% of patients in the Kaletra group. The press release did not report the percentage of patients in either group who had viral loads below 50 copies/mL after 48 weeks – the best viral load result that can be achieved using anti-HIV treatment. Neither was there a mention of T-cell comparisons between the two groups.

Both regimens were generally well-tolerated. A total of 6% of patients withdrew due to adverse events. While the press release did not describe the adverse events, it did say that they were consistent with those already known to occur with Lexiva/Norvir and Kaletra.

According to GlaxoSmithKline and Vertex, Lexiva/Norvir was compared to Kaletra due to Kaletra's position as the preferred HIV protease inhibitor for HIV-positive patients beginning treatment for the first time in HIV treatment guidelines developed by the United States Department of Health and Human Services (DHHS) and the International AIDS Society (IAS).

The validity of these preliminary results have not yet been publicly reviewed by HIV experts not associated with the study. GlaxoSmithKline will present these and other data at a medical conference in 2006.

Sources:

GlaxoSmithKline and Vertex Pharmaceuticals