Drugs & Medication

Protease inhibitors (PIs) are a class of medication used to treat or prevent infection by viruses, including HIV and Hepatitis C. PIs prevent viral replication by inhibiting the activity of protease, an enzyme used by the viruses to cleave nascent proteins for final assembly of new virons.

Protease inhibitors have been developed or are presently undergoing testing for treating various viruses:

• HIV/AIDS: antiretroviral protease inhibitors (saquinavir, ritonavir, indinavir, nelfinavir etc.)
  Hepatitis C: experimental agents: BILN 2061, VX 950.

Given the specificity of the target of these drugs there is the risk, as in antibiotics, of the development of drug-resistant mutated viruses. To reduce this risk it is common to use together different drugs aimed at different targets.

Antiretrovirals

Protease inhibitors were the second class of antiretroviral drugs developed. In all cases, patents remain in force until 2010 or beyond.

Saquinavir 

Saquinavir has trade names Fortovase® (soft gel capsule) and Invirase® (hard gel capsule).

Ritonavir 

Ritonavir has the trade name: Norvir®.

Indinavir 

Indinavir has the trade name: Crixivan®.

Nelfinavir 

Nelfinavir has the trade name Viracept®.

Amprenavir 

Amprenavir has the trade name Agenerase®. The FDA approved it April 15, 1999, making it the sixteenth FDA-approved antiretroviral. It was the first protease inhibitor approved for twice-a-day dosing instead of needing to be taken every eight hours. The convenient dosing came at a price, as the dose required is 1,200mg, delivered in eight very large gel capsules. Production of Agenerase® was discontinued by the manufacturer December 31, 2004, as it has been superseded by fosamprenavir.

Lopinavir 

Lopinavir is only marketed as a combination. See Kaletra® below.

Atazanavir

Atazanavir has the trade name Reyataz®.

Fosamprenavir 

Fosamprenavir, with the trade name Lexiva®, is a pro-drug of amprenavir. The FDA approved it October 20, 2003. The human body metabolizes fosamprenavir in order to form amprenavir, which is the active ingredient. That metabolization increases the duration that amprenavir is available, making fosamprenavir a slow-release version of amprenavir and thus reduces the amount of pills required versus standard amprenavir.

Tipranavir 

Tipranavir, also known as tipranavir disodium, has the trade name Aptivus®.

References

A brief history of the development of protease inhibitors by Hoffman La Roche, Abbott, and Merck: http://inventors.about.com/library/inventors/bl_protease_inhibitors.htm