Study AI455-099 was a 48-week, randomised, double-blind study with Zerit (40 mg twice daily), in combination with lamivudine (150 mg twice daily) plus efavirenz (600 mg once daily), in 391 treatment-naive patients, with a median CD4 cell count of 272 cells/ mm3 (range 61 to 1,215 cells/ mm3) and a median plasma HIV-1 RNA of 4.80 log10 copies/ ml (range 2.6 to 5.9 log 10 copies/ ml) at baseline.