Emtricitabine (commonly called FTC, systematic name 2',3'-dideoxy-5-fluoro-3'-thiacytidine), with trade name Emtriva (formerly Coviracil), is a nucleoside reverse-transcriptase inhibitor (NRTI) for the prevention and treatment of HIV infection in adults and children. In 2019, it was the 494th most commonly prescribed medication in the United States, with more than 3thousand prescriptions. Emtricitabine makes up one fourth of the Quad pill (brand names: Stribild and Genvoya). It is also marketed in a fixed-dose combination with tenofovir disoproxil (Viread) under the brand name Truvada, and with

tenofovir alafenamide Tenofovir alafenamide, sold under the brand name Vemlidy, is an antiviral medication used against hepatitis B and HIV. It is used for the treatment of chronic hepatitis B virus (HBV) infection in adults with compensated liver disease an ...

(Vemlidy) under the brand name Descovy. In fixed-dose combinations with tenofovir or with efavirenz and tenofovir it is on the World Health Organization's List of Essential Medicines. A fixed-dose triple combination of emtricitabine, tenofovir and efavirenz (Sustiva, marketed by Bristol-Myers Squibb) was approved by the U.S. Food and Drug Administration (FDA) on July 12, 2006, under the brand name Atripla.

Medical uses

HIV infection

Emtricitabine is indicated in combination with other antiretroviral agents for the prevention and treatment of HIV-1 infection.

HBV infection

Emtricitabine exhibits clinical activity against the hepatitis B virus (HBV), but is not approved by the U.S.

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(FDA) for the treatment of HBV infection. Among individuals with chronic HBV infection, emtricitabine treatment results in significant histologic, virologic, and biochemical improvement. The safety profile of emtricitabine during treatment is similar to that of a placebo. Emtricitabine, like all other FDA approved drugs, cures neither HIV nor HBV infection. In a study involving individuals with HBV infection, symptoms of infection returned in 23% of emtricitabine-treated individuals who were taken off therapy. In studies involving individuals with ''chronic'' HIV infection, viral replication also resumes when study subjects are taken off therapy. As with drugs used to treat HIV infection, drugs used to treat HBV infection may have to be used in combination to prevent the evolution of drug resistant strains. The effectiveness of emtricitabine in combination with other anti-HBV drugs has not been established.

Side effects

In clinical practice,

toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect o ...

with emtricitabine is unusual. The most common treatment-related adverse events are

diarrhea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

headache A headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of Depression (mood), depression in those with severe ...

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat. Over 30 d ...

, and rash. These symptoms are generally mild to moderate in severity, but they caused 1% of clinical trial patients to give up treatment. Skin discoloration, which is typically reported as

hyperpigmentation Hyperpigmentation, also known as the dark spots or circles on the skin, is the darkening of an area of Human skin, skin or nail (anatomy), nails caused by increased melanin. Causes Hyperpigmentation can be caused by sun damage, inflammation, or ...

and usually affects either the palms of the hands or the soles of the feet, is reported in less than 2% of individuals and is almost exclusive to patients of African origin. Among the more severe side effects patients may experience are a hepatotoxicity or a lactic acidosis.

Mechanism of action

Emtricitabine is an analogue of cytidine. The drug works by inhibiting

reverse transcriptase A reverse transcriptase (RT) is an enzyme used to convert RNA genome to DNA, a process termed reverse transcription. Reverse transcriptases are used by viruses such as HIV and hepatitis B to replicate their genomes, by retrotransposon mobi ...

, the enzyme that copies HIV RNA into new viral DNA. By interfering with this process, which is central to the replication of HIV, emtricitabine can help to lower the amount of HIV, or " viral load", in a patient's body and can indirectly increase the number of

immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...

cells (namely

T cell T cells (also known as T lymphocytes) are an important part of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell ...

s/ CD4+ T-cells). Both of these changes are associated with healthier immune systems and decreased likelihood of serious illness.

History

Emtricitabine was discovered by Dennis C. Liotta, Raymond F. Schinazi, and Woo-Baeg Choi of

Emory University Emory University is a private university, private research university in Atlanta, Georgia, United States. It was founded in 1836 as Emory College by the Methodist Episcopal Church and named in honor of Methodist bishop John Emory. Its main campu ...

and licensed to Triangle Pharmaceuticals by Emory in 1996 in a collaboration with Dr. Yung-Chi Cheng at

Yale University Yale University is a Private university, private Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the List of Colonial Colleges, third-oldest institution of higher education in the United Stat ...

. Triangle Pharmaceuticals was acquired in 2003 by Gilead Sciences, which completed development and now markets the product with the brand name Emtriva. It was approved by the FDA July 2, 2003.Standard & Poor's 500 Guide
. Standard & Poor's, McGraw-Hill, (2004), p. 83. It is very similar to lamivudine (3TC) and cross-resistance between the two is near-universal.

References

External links

* {{Portal bar , Medicine , Viruses Gilead Sciences Hepatotoxins Nucleoside analog reverse transcriptase inhibitors Oxathiolanes Organofluorides Pyrimidones Hydroxymethyl compounds