Protease inhibitors

For natural protease inhibitors, please see protease inhibitor (biology)

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 HIV-1 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

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

Name | Trade name | Company | Patent | Notes

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Saquinavir | Fortovase, Invirase | Hoffmann–La Roche | U.S. Patent 5,196,438 | It was the first protease inhibitor approved by the FDA (December 6, 1995).
Ritonavir | Norvir | Abbott Laboratories | U.S. Patent 5,541,206 | \-
Indinavir | Crixivan | Merck & Co. | U.S. Patent 5,413,999 | \-
Nelfinavir | Viracept | Japan Tobacco | U.S. Patent 5,484,926 | \-
Amprenavir | Agenerase | GlaxoSmithKline | U.S. Patent 5,585,397 | 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 Production was discontinued by the manufacturer December 31, 2004, as it has been superseded by fosamprenavir.
Lopinavir | Kaletra | Abbott | - | Is only marketed as a combination, with ritonavir.
Atazanavir | Reyataz | - | - | \-
Fosamprenavir | Lexiva | GlaxoSmithKline | - | 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 number of pills required versus standard amprenavir.
Tipranavir | Aptivus | Boehringer-Ingelheim | - | Also known as tipranavir disodium
Darunavir | Prezista | Tibotec | - | It was approved by the Food and Drug Administration (FDA) on June 23, 2006. Several ongoing  phase III trials are showing a high efficiency for the PREZISTA/rtv combination being superior to the lopinavir/rtv combination for first-line therapy[1]. Darunavir is the first drug in a long time that didn't come with a price increase. It leapfrogged two other approved drugs of its type, and is matching the price of a third [2][3][4].

## References

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1. ↑ Darunavir-ritonavir more effective than Lopinavir-ritonavir in HIV infected, treatment-experienced patients,The Lancet, Volume 370, Number 9581, 07 July 2007, http://www.thelancet.com/journals/lancet/issue?volume=370&issue=9581
2. ↑ Liz Highleyman, Patient Advocates Commend Pricing of New PI Darunavir, http://www.hivandhepatitis.com/recent/2006/ad1/063006_a.html
3. ↑ [Darunavir - first molecule to treat drug-resistant HIV, http://www.news-medical.net/?id=19211]
4. ↑ [Retaining Efficacy Against Evasive HIV, http://pubs.acs.org/cen/news/84/i34/8434drugdesign.html]

* A brief history of the development of protease inhibitors by Hoffman La Roche, Abbott, and Merck

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Antivirals, other than for HIV (primarily J05, also S01AD and D06BB)

Anti-herpesvirus (DNA, I)|

guanine analogues (Aciclovir, Famciclovir, Ganciclovir, Penciclovir, Valaciclovir, Valganciclovir) • nucleoside analogues (Idoxuridine, Trifluridine, Vidarabine) • Cidofovir • Docosanol • Fomivirsen • Foscarnet • Tromantadine

HPV/MC (DNA, I)|

Imiquimod • Podophyllotoxin

Hepatitis B (DNA, VII)|

Adefovir • Interferon alfa-2b • Pegylated interferon alfa-2a • Entecavir • Lamivudine • Telbivudine • Tenofovir†

Hepatitis C (RNA, IV)|

Pegylated interferon alpha • Ribavirin • Taribavirin† • Boceprevir†

Picornavirus (RNA, IV)|

Pleconaril†

Anti-influenza agents (RNA, V)|

Arbidol

adamantane derivatives/M2 inhibitors (Amantadine, Rimantadine)

neuraminidase inhibitors (Oseltamivir, Zanamivir, Peramivir†)

HIV (Reverse, VI)|

See HIV pharm

Other antiviral agents|

general (Inosine, Interferon)

†Undergoing clinical trials, not FDA approved.

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