Vertex Pharmaceuticals Incorporated reported preliminary 48-week data from the CONTEXT study conducted by GlaxoSmithKline of the investigational HIV protease inhibitor (PI) 433908 (908).

The CONTEXT study, an open-label Phase III clinical trial, enrolled 320 treatment-experienced patients with prior virologic failure. The study was designed to assess the safety and efficacy of once daily (QD) or twice daily (BID) dosing of 908 boosted with ritonavir compared to a third treatment arm with the PI lopinavir/ritonavir (LPV/r) BID, all in combination with two nucleoside reverse transcriptase inhibitors, in patients with prior HIV PI treatment experience. The primary objectives of the CONTEXT study were to assess antiviral efficacy and safety of the three study regimens at 24 and 48 weeks.

Top-line results of the study indicate that 908 exhibited antiviral activity in treatment-experienced patients. In an evaluation of time-averaged change in viral load (AAUCMB), which was the primary endpoint of the study, non-inferiority of 908/r BID and 908/r QD compared to LPV/r BID could not be established at 48 weeks. However, in an analysis of the proportion of patients with viral load below 400 copies/mL, 908/r BID (58%) and LPV/r BID (61%) demonstrated comparable levels of antiviral activity. The proportion of patients who achieved vRNA below 50 copies/mL at 48 weeks was also similar in the 908/r BID (46%) and LPV/r BID (50%) arms.

Vertex anticipates that 908 can be approved and launched in the United States in the fourth quarter of 2003 and in European countries beginning in 2004.