Alovudine (3’ -deoxy-3’ fluorothymidine) is a nucleoside reverse transcriptase inhibitor (NRTI) initially tested in the early 1990s, before the era of combination therapy and before the availability of plasma viral load measurement. Initial toxicity studies showed that the primary target organ of toxicity was the bone marrow. A lack of clear advantages in activity over zidovudine, the only drug approved in the early 1990s, and the potential for bone marrow toxicity caused alovudine development to be stopped [6]. However, later in vitro studies found alovudine to be very effective at suppressing several NRTI-resistant HIV-1 mutants, including isolates with multiple thymidine-associated mutations (TAMs) or multi-NRTI-resistance mutations. Alovudine at a dose of 7.5 mg/day added to a failing antiretroviral combined regimen in patients with isolates resistant to other NRTIs yielded a median viral load decline after a 4-week period in patients not receiving concomitant stavudine. In July 2003, Medivir out-licensed it's HIV antiviral MIV-310 to Boehringer Ingelheim. Under the terms of the agreement, Boehringer Ingelheim will make upfront and milestone payments to Medivir totaling up to 122 million euro in the event that all development and performance milestones are met. In March 2005, Boehringer Ingelheim recently completed a clinical trial of MIV-310 (alovudine) in HIV/AIDS. The efficacy exhibited by MIV-310 at the doses tested showed antiviral activity but did not achieve the target level of efficacy which had previously been defined. Boehringer Ingelheim, therefore, decided to stop the development of this investigational drug.