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As of the end of 2004, an estimated 39.4 million people worldwide – 37.2 million adults and
2.2 children younger than 15 years – were living with Human Immunodeficiency virus (HIV)
infection/Acquired Immunodeficiency Syndrome (AIDS).
Current treatment options consist of four different mechanistic classes of compounds:
- NRTIs (nucleoside/nucleotide reverse transcriptase inhibitors) inhibiting the
reverse transcriptase (RT) of HIV by structural similarity with the substrate of
- NNRTIs (non-nucleoside reverse transcriptase inhibitors) inhibiting the
reverse transcriptase of HIV without being nucleosides analogues.
- PIs (protease inhibitors) inhibiting the HIV protease which is an enzyme
required for the assembly and release of mature HIV particles from the cell
after the replication cycle.
- Entry inhibitors: there is currently only one compound authorised which is a
fusion inhibitor, (inhibits fusion of the HIV with CD4+ cells, hence infection
Regimens containing one or more of these agents are required for building combination
antiretroviral therapies. The choice of the combination regimens depends on several factors
such as the status of the patient, particularly in terms of plasma viral load (HIV RNA), CD4
cell counts, previous treatment(s), prior relapse and intolerance to treatment. The long-term
use of all these products is, however, hampered by different factors such by the emergence of
resistance, by potential toxicity and in some cases by inconvenient dosing schedules or
formulations. Further therapeutic agents are therefore needed, particularly in patients who
have failed their therapy and who have no or few remaining treatment options.
PREZISTA, which contains darunavir, a protease inhibitor, has been developed for highly