GlaxoSmithKline (GSK) and Vertex Pharmaceuticals Incorporated announced preliminary 48-week results from a head-to-head clinical study that indicated that Lexiva (Telzir; fosamprenavir calcium) 700 mg plus ritonavir 100 mg given twice daily was comparable (non-inferior) to Kaletra (lopinavir/ritonavir fixed-dose combination) given twice daily in treatment-naïve HIV patients. All patients in the study also received a once-daily fixed-dose combination of abacavir 600 mg and lamivudine 300 mg as the backbone of antiretroviral therapy.

The results will be submitted to the FDA and other health regulatory authorities when the final analysis is concluded.

Lexiva/ritonavir was compared to Kaletra in this study due to Kaletra's position as the preferred HIV protease inhibitor in HIV treatment guidelines developed by the United States Department of Health and Human Services (DHHS) and the International AIDS Society (IAS). Based on these results from this study, researchers have concluded that Lexiva appears to be comparable to Kaletra and has met the primary endpoints of this non-inferiority trial.

GSK will present results from the study at a medical conference in 2006. Lexiva was co-discovered by Vertex and GlaxoSmithKline.