In the initial CHARM study, the effect of adding nevirapine and/or hydrea to a triple NRTI regimen (trizivir i.e. abacavir, lamivudine and zidovudine) in terms of efficacy and tolerability was investigated in anti retroviral naïve patients. The primary endpoint was treatment failure and follow up was 72 weeks. A total of 229 patients were included. The use of hydrea was prematurely stopped because adding hydrea significantly contributed to treatment failure through enhancement of the toxicities associated with its use. Subjects in the nevirapine group reached a plasma HIV-1 RNA level < 50 copies/ml quicker (log rank test p = 0.011). In addition, in an as treated analysis only 16.2% of subjects adding nevirapine versus 39.5% adding no nevirapine reached the primary endpoint (p=0.027). These results resemble the findings in the ACTG A5059 study. The trizivir arm of this ACTG study was stopped, because anti-retroviral naïve subjects randomized to receive trizivir experienced virological failure earlier and more frequent than subjects who were randomized to receive either of the two other treatment regimens being evaluated in that study. The two other treatment regimens were: