During the last stage of the virus replication, the protease enzyme is necessary for the final assembly of the new HIV viruses. The protease inhibitors block the protease enzyme, interfering with the replication process. In this way, these drugs are able to limit the spread of the HIV viruses.

These drugs have not been approved by the Food and Drug Administration(FDA) for use against HIV.

GW640385 by GlaxoSmithKline (Phase I)

GW640385 is effective aginast both the HIV virus without any antibiotic-resistance gene and virus that already has resistance to existing protease inhibitors. Its relatively low dose could mean less side effects, but it will probably be boosted with ritonavir.

RO033-4649 by Roche (Phase I)

R0033-4649 was selected for its good activity against HIV that is already very resistant to existing protease inhibitors.

For more information, please visit R0033-4649.

Tipranavir (PNU-140690) by Boehringer Ingelheim

Tipranavir appears to work against HIV that is already resistant to current protease inhibitors. It is being studied in twice-daily dosing combined with ritonavir and seems to have a high rate of side effects such as diarrhea, nausea and vomiting.

TMC114 by Tibotec

TMC114 shows very rapid drops in viral load, but its side effects include diarrhea, gas, headache and dizziness.