HIV-1-infected, clinically stable, treatment-naïve adults who have completed 96-weeks of elvucitabine therapy in protocol ACH443-015 and whose HIV RNA levels remain below 50 copies/mL from the 92-week assessment in protocol ACH443-015 or subjects who have completed 48-weeks of elvucitabine therapy in protocol ACH443-018 and continue to maintain a HIV-1 RNA viral load below their baseline level upon entry into protocol ACH443-018