Tenofovir (top) and tenofovir disoproxil fumarate (bottom)
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Tenofovir disoproxil, marketed by Gilead Sciences under the trade name Viread (as the fumarate, TDF), belongs to a class of antiretroviral drugs known as nucleotide analogue reverse transcriptase inhibitors (NRTIs), which block reverse transcriptase, a crucial viral enzyme in human immunodeficiency virus 1 (HIV-1) and hepatitis B virus infections.
It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.
- HIV-1 infection: Tenofovir is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection in adults and pediatric patients 2 years of age and older. This indication is based on analyses of plasma HIV-1 RNA levels and CD4 cell counts in controlled studies of tenofovir in treatment-naive and treatment-experienced adults.
- Tenofovir is indicated for the treatment of chronic hepatitis B in adults and pediatric patients 12 years of age and older.
HIV risk reduction
A Cochrane review examined the use of tenofovir as a pre-exposure prophylaxis against HIV infection. It found that both tenofovir alone and the tenofovir/emtricitabine combination significantly decreased the risk of contracting HIV.
The U. S. Centers for Disease Control and Prevention (CDC) conducted a study in partnership with the Thailand Ministry of Public Health to ascertain the effectiveness of providing people who inject drugs illicitly with daily doses of the antiretroviral drug tenofovir as a prevention measure. The results of the study were released in mid-June 2013 and revealed a 48.9%-reduced incidence of the virus among the group of subjects who received the drug, in comparison to the control group who received a placebo. The principal investigator of the study stated: "We now know that pre-exposure prophylaxis can be a potentially vital option for HIV prevention in people at very high risk for infection, whether through sexual transmission or injecting drug use."
The most common side effects associated with tenofovir include nausea, vomiting, diarrhea, and asthenia. Less frequent side effects include hepatotoxicity, abdominal pain, and flatulence. Tenofovir has also been implicated in causing renal toxicity, particularly at elevated concentrations.
Tenofovir can cause acute renal failure, Fanconi syndrome, proteinuria, or tubular necrosis. These side effects are due to accumulation of the drug in proximal tubules. Tenofovir can interact with didanosine by increasing didanosine's concentration. It also decreases the concentration of atazanavir sulfate.
Tenofovir was initially synthesized by Antonín Holý at the Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic in Prague. The patent filed by Holý in 1984 makes no mention of the potential use of the compound for the treatment of HIV infection, which had only been discovered one year earlier.
In 1985, De Clercq and Holy described the activity of PMPA against HIV in cell culture. Shortly thereafter, a collaboration with the biotechnology company Gilead Sciences led to the investigation of PMPA's potential as a treatment for HIV infected patients. In 1997 researchers from Gilead and the University of California, San Francisco demonstrated that tenofovir exhibits anti-HIV effects in humans when dosed by subcutaneous injection.
The initial form of tenofovir used in these studies had limited potential for widespread use because it was not absorbed when administered orally. A medicinal chemistry team at Gilead developed a modified version of tenofovir, tenofovir disoproxil fumarate. This version of tenofovir, which is the only version used clinically today, is often referred to simply as "tenofovir". In this version of the drug, the two negative charges of the tenofovir phosphonic acid group are masked, thus enhancing oral absorption.
Tenofovir disoproxil is a prodrug form of tenofovir. It is also marketed under the brand name Reviro by Dr. Reddy's Laboratories. Tenofovir is also available in a fixed-dose combination with emtricitabine in a product with the brand name Truvada for once-a-day dosing. Atripla, a fixed-dose triple combination of tenofovir, emtricitabine, and efavirenz, was approved by the FDA on 12 July 2006 and is now available, providing a single daily dose for the treatment of HIV.
Therapeutic drug monitoring
Tenofovir may be measured in plasma by liquid chromatography. Such testing is useful for monitoring therapy and to prevent drug accumulation and toxicity in patients with renal or hepatic impairment.
- Emau P; Jiang Y; Agy MB et al. (2006). "Post-exposure prophylaxis for SIV revisited: Animal model for HIV infection". AIDS Res Ther 3: 29. doi:10.1186/1742-6405-3-29. PMC 1687192. PMID 17132170.
- Gilead Sciences, Inc. Prescribing Information. Revised: November 2012.
- "WHO Model List of EssentialMedicines" (PDF). World Health Organization. October 2013. Retrieved 22 April 2014.
- Guidelines for the prevention, care and treatment of persons with chronic hepatitis B infection, WHO, Publication details:Pages: 166 Publication date: March 2015 Languages: English ISBN 978 92 4 154905 9
- Okwundu CI, Uthman OA, Okoromah CAN (2012). "Antiretroviral pre-exposure prophylaxis (PrEP) for preventing HIV in high-risk individuals". Cochrane Database Syst Rev 7 (7): CD007189. doi:10.1002/14651858.CD007189.pub3. PMID 22786505.
- Emma Bourke (14 June 2013). "Preventive drug could reduce HIV transmission among injecting drug users". The Conversation Australia. The Conversation Media Group. Retrieved 17 June 2013.
- USPDI. Thompson. 2005. pp. 2741–2.
- "Viread Prescribing Guidelines" (PDF). U.S. Food and Drug Administration. March 2006. Archived from the original (PDF) on 2007-09-30. Retrieved 2007-02-12.
- "Patent US4808716 - 9-(phosponylmethoxyalkyl) adenines, the method of preparation and ... - Google Patents".
- A US 4724233 A, De Clercq, Erik; Antonin Holy & Ivan Rosenberg, "Therapeutical application of phosphonylmethoxyalkyl adenines", published 1985-04-25
- Deeks SG, Barditch-Crovo P, Lietman PS et al. (September 1998). "Safety, pharmacokinetics, and antiretroviral activity of intravenous 9-[2-(R)-(Phosphonomethoxy)propyl]adenine, a novel anti-human immunodeficiency virus (HIV) therapy, in HIV-infected adults". Antimicrob. Agents Chemother. 42 (9): 2380–4. PMC 105837. PMID 9736567.
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- FDA letter of approval (regarding treatment of hepatitis B)
- FDA Clears Viread for Hepatitis B
- Delahunty T, Bushman L, Robbins B, Fletcher CV (2009). "The simultaneous assay of tenofovir and emtricitabine in plasma using LC/MS/MS and isotopically labeled internal standards". J. Chrom. B 877 (20–21): 1907–1914. doi:10.1016/j.jchromb.2009.05.029.
- Kearney BP, Yale K, Shah J, Zhong L, Flaherty JF (2006). "Pharmacokinetics and dosing recommendations of tenofovir disoproxil fumarate in hepatic or renal impairment". Clin. Pharmacokinet. 45 (11): 1115–24. doi:10.2165/00003088-200645110-00005. PMID 17048975.
- R. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 8th edition, Biomedical Publications, Foster City, California, 2008, pp. 1490–1492.