New amprenavir formulation equal to nelfinavir

The NEAT study compared the use of a new formulation of amprenavir (GW433908), taken as two pills twice daily, to the widely prescribed protease inhibitor nelfinavir (five pills twice a day). All participants took abacavir and 3TC twice daily. 166 people were randomized to the GW-908 group and 83 to the nelfinavir group. Median CD4 count and baseline viral load in the two groups were 214 and 212, 4.82 and 4.85 log copies/ml (approximately 65,000 copies/ml). Forty-five per cent had viral load above 100,000 copies/ml at baseline, and 20% already had an AIDS diagnosis at baseline.

After 48 weeks, 54% of the GW-908 group and 40% of the nelfinavir group had viral load below 50 copies/ml (non-significant difference); in those with baseline viral load above 100,000 copies/ml, 71% of the GW-908 group and 35% of the nelfinavir group had viral load below 400 copies/ml. In those with baseline viral load above 100,000 copies/ml, 42% of the GW-908 group and 11% of the nelfinavir group. Of note in tis study is the fact that GW-908 achieved these results without ritonavir boosting, and in strong contrast to the pivotal study of amprenavir in treatment-naïve patients, PROAB3003, in which amprenavir performed miserably.

The only significant difference in adverse events was the greater frequency of grade 2-4 diarrhoea in the nelfinavir group (17% vs 5%, p=0.003). The low level of diarrhoea seen in this study is in contrast to previous studies of the licensed amprenavir formulation (see Amprenavir - key research on this website for further details). Overall, the drugs were relatively well tolerated; 31% of the nelfinavir group and 28% of the GW-908 group experienced grade 2-4 adverse events. Metabolic parameters did not differ between the two groups, and median levels remained within the upper range of normal (HDL cholesterol recovered towards normal levels by week 24). Triglyceride and total cholesterol levels did not increase significantly in either group, but LDL cholesterol increased by approximately 20mg/dL in both groups by week 24.