Direct-acting Antivirals
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Direct-acting Antivirals
Direct-acting antivirals (DAA) are drugs used to treat hepatitis C infections. They are a combination of antiviral drugs that target stages of the hepatitis C virus reproductive cycle. They are more effective than older treatments such as ribavirin and interferon. The DAA drugs are taken orally, as tablets, for 8 to 12 weeks. The treatment depends on the type or types (genotypes) of hepatitis C virus that are causing the infection. Both during and at the end of treatment, blood tests are used to monitor the effectiveness of the treatment and subsequent cure. The DAA combination drugs used include: * Harvoni (sofosbuvir and ledipasvir) * Epclusa (sofosbuvir and velpatasvir) * Vosevi (sofosbuvir, velpatasvir, and voxilaprevir) * Zepatier (elbasvir and grazoprevir) * Mavyret (glecaprevir and pibrentasvir) DAAs were approved on the basis of a surrogate endpoint In clinical trials, a surrogate endpoint (or surrogate marker) is a measure of effect of a specific treatment that may corre ...
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Hepatitis C
Hepatitis C is an infectious disease caused by the hepatitis C virus (HCV) that primarily affects the liver; it is a type of viral hepatitis. During the initial infection people often have mild or no symptoms. Occasionally a fever, dark urine, abdominal pain, and yellow tinged skin occurs. The virus persists in the liver in about 75% to 85% of those initially infected. Early on, chronic infection typically has no symptoms. Over many years however, it often leads to liver disease and occasionally cirrhosis. In some cases, those with cirrhosis will develop serious complications such as liver failure, liver cancer, or dilated blood vessels in the esophagus and stomach. HCV is spread primarily by blood-to-blood contact associated with injection drug use, poorly sterilized medical equipment, needlestick injuries in healthcare, and transfusions. Using blood screening, the risk from a transfusion is less than one per two million. It may also be spread from an infected mother to her ...
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Antiviral Drug
Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Unlike most antibiotics, antiviral drugs do not destroy their target pathogen; instead they inhibit its development. Antiviral drugs are one class of antimicrobials, a larger group which also includes antibiotic (also termed antibacterial), antifungal and antiparasitic drugs, or antiviral drugs based on monoclonal antibodies. Most antivirals are considered relatively harmless to the host, and therefore can be used to treat infections. They should be distinguished from viricides, which are not medication but deactivate or destroy virus particles, either inside or outside the body. Natural viricides are produced by some plants such as eucalyptus and Australian tea trees. Medical uses Most of the antiviral drugs now available are designed to help deal with HIV, herpes viruses, th ...
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Hepatitis C Virus
The hepatitis C virus (HCV) is a small (55–65 nm in size), enveloped, positive-sense single-stranded RNA virus of the family ''Flaviviridae''. The hepatitis C virus is the cause of hepatitis C and some cancers such as liver cancer ( hepatocellular carcinoma, abbreviated HCC) and lymphomas in humans. Taxonomy The hepatitis C virus belongs to the genus ''Hepacivirus'', a member of the family ''Flaviviridae''. Before 2011, it was considered to be the only member of this genus. However a member of this genus has been discovered in dogs: canine hepacivirus. There is also at least one virus in this genus that infects horses. Several additional viruses in the genus have been described in bats and rodents. Structure The hepatitis C virus particle consists of a lipid membrane envelope that is 55 to 65 nm in diameter. Two viral envelope glycoproteins, E1 and E2, are embedded in the lipid envelope. They take part in viral attachment and entry into the cell. Within the envel ...
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Ribavirin
Ribavirin, also known as tribavirin, is an antiviral medication used to treat RSV infection, hepatitis C and some viral hemorrhagic fevers. For hepatitis C, it is used in combination with other medications such as simeprevir, sofosbuvir, peginterferon alfa-2b or peginterferon alfa-2a. Among the viral hemorrhagic fevers it is used for Lassa fever, Crimean–Congo hemorrhagic fever, and Hantavirus infection but should not be used for Ebola or Marburg infections. Ribavirin is taken by mouth or inhaled. Common side effects include feeling tired, headache, nausea, fever, muscle pains, and an irritable mood. Serious side effects include red blood cell breakdown, liver problems, and allergic reactions. Use during pregnancy results in harm to the baby. Effective birth control is recommended for both males and females for at least seven months during and after use. The mechanism of action of ribavirin is not entirely clear. Ribavirin was patented in 1971 and approved for medical us ...
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Interferon
Interferons (IFNs, ) are a group of signaling proteins made and released by host cells in response to the presence of several viruses. In a typical scenario, a virus-infected cell will release interferons causing nearby cells to heighten their anti-viral defenses. IFNs belong to the large class of proteins known as cytokines, molecules used for communication between cells to trigger the protective defenses of the immune system that help eradicate pathogens. Interferons are named for their ability to "interfere" with viral replication by protecting cells from virus infections. However, virus-encoded genetic elements have the ability to antagonize the IFN response contributing to viral pathogenesis and viral diseases. IFNs also have various other functions: they activate immune cells, such as natural killer cells and macrophages, and they increase host defenses by up-regulating antigen presentation by virtue of increasing the expression of major histocompatibility complex (M ...
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Genotype
The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a specific gene depends on the number of copies of each chromosome found in that species, also referred to as ploidy. In diploid species like humans, two full sets of chromosomes are present, meaning each individual has two alleles for any given gene. If both alleles are the same, the genotype is referred to as homozygous. If the alleles are different, the genotype is referred to as heterozygous. Genotype contributes to phenotype, the observable traits and characteristics in an individual or organism. The degree to which genotype affects phenotype depends on the trait. For example, the petal color in a pea plant is exclusively determined by genotype. The petals can be purple or white depending on the alleles present in the pea plant. Howev ...
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Harvoni
Ledipasvir/sofosbuvir, sold under the trade name Harvoni among others, is a medication used to treat hepatitis C. It is a fixed-dose combination of ledipasvir and sofosbuvir. Cure rates are 94% to 99% in people infected with hepatitis C virus (HCV) genotype 1. Some evidence also supports use in HCV genotype 3 and 4. It is taken daily by mouth for 8–24 weeks. It is generally well tolerated. Common side effects include muscle pains, headache, nausea, rash, and cough. It is unclear if use in pregnancy is safe for the baby. Ledipasvir works by decreasing the activity of NS5A and sofosbuvir works by decreasing the activity of NS5B polymerase. Ledipasvir/sofosbuvir was approved for medical use in the United States, in the European Union, and in Canada in 2014. It is on the World Health Organization's List of Essential Medicines. Medical uses Cure rates are 94% to 99% in people infected with genotype 1 (46% of HCV cases). It has also been evaluated for the treatment of infection ...
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Epclusa
Sofosbuvir/velpatasvir, sold under the brand name Epclusa among others, is a fixed-dose combination medication for the treatment of hepatitis C in adults. It combines sofosbuvir and velpatasvir. It is more than 90% effective for hepatitis C genotypes one through six. It also works for hepatitis C in those who also have cirrhosis or HIV/AIDS. It is taken by mouth. In March 2020, sofosbuvir/velpatasvir was approved for use in the United States to treat hepatitis C virus (HCV) in children ages six years and older or weighing at least 37 pounds (17 kilograms) with any of the six HCV genotypes—or strains—without cirrhosis (liver disease) or with mild cirrhosis. Sofosbuvir/velpatasvir in combination with ribavirin is indicated for the treatment of children six years and older or weighing at least 37 pounds with severe cirrhosis. The combination is generally well tolerated. Common side effects include headaches, fatigue, trouble sleeping, and nausea. The combination has not been ...
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Vosevi
Sofosbuvir/velpatasvir/voxilaprevir, sold under the brand name Vosevi, is a fixed-dose combination medication for the treatment of hepatitis C. It combines three drugs that each act by a different mechanism of action against the hepatitis C virus: sofosbuvir, velpatasvir, and voxilaprevir.Vosevi was approved for medical use in the United States and in the European Union in July 2017. Vosevi is sold by Gilead Sciences Gilead Sciences, Inc. () is an American biopharmaceutical company headquartered in Foster City, California, that focuses on researching and developing antiviral drugs used in the treatment of HIV/AIDS, hepatitis B, hepatitis C, influenza, and CO .... References External links * Combination drugs NS3/4A protease inhibitors NS5B (polymerase) inhibitors NS5A inhibitors {{antiinfective-drug-stub ...
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Zepatier
Elbasvir/grazoprevir (trade name Zepatier ) is a fixed-dose combination for the treatment of hepatitis C, containing elbasvir (an inhibitor of hepatitis C virus's NS5A protein) and grazoprevir (an NS3 (HCV), NS3/NS4A, 4A inhibitor). It is used to treat chronic hepatitis C virus (HCV) genotypes 1 or 4 infection in both treatment-naïve and treatment-experienced patients. Both elbasvir and grazoprevir were developed by Merck & Co. The US Food and Drug Administration (FDA) approved the drug on 28 January 2016. Medical uses Elbasvir/grazoprevir received FDA approval in January 2016. Its indication is for treatment of chronic hepatitis C of the genotypes 1 and 4 for adults. Hepatitis C is a global disease that infects upwards of 150 million people worldwide, especially in older generations. Hepatitis C causes inflammation of the liver that eventually leads to diminished liver function or even failure. Zepatier is indicated for treatment with or without use of ribavirin, as well. Zepa ...
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Mavyret
Glecaprevir/pibrentasvir (G/P), sold under the brand names Mavyret and Maviret, is a fixed-dose combination medication used to treat hepatitis C. It contains glecaprevir and pibrentasvir. It works against all six types of hepatitis C. At twelve weeks following treatment between 81% and 100% of people have no evidence of hepatitis C. It is taken once a day by mouth with food. The most common side effects are headache, diarrhea, and tiredness. In those with a history of hepatitis B reactivation may occur. It is not recommended in people with moderate to severe liver disease. Glecaprevir works by blocking the protein NS3/ 4A protease, while pibrentasvir works by blocking NS5A. The combination was approved for medical use in the United States and Europe in 2017. It is on the World Health Organization's List of Essential Medicines. Medical uses In the United States, G/P is used to treat adults and children aged 12 years and older or weighing at least 99 pounds with chronic hepa ...
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Surrogate Endpoint
In clinical trials, a surrogate endpoint (or surrogate marker) is a measure of effect of a specific treatment that may correlate with a ''real'' clinical endpoint but does not necessarily have a guaranteed relationship. The National Institutes of Health (USA) defines surrogate endpoint as "a biomarker intended to substitute for a clinical endpoint". Surrogate markers are used when the primary endpoint is undesired (e.g., death), or when the number of events is very small, thus making it impractical to conduct a clinical trial to gather a statistically significant number of endpoints. The FDA and other regulatory agencies will often accept evidence from clinical trials that show a direct clinical benefit to surrogate markers. Surrogate endpoints can be obtained from different modalities, such as, behavioural or cognitive scores, or biomarkers from Electroencephalography ( qEEG), MRI, PET, or biochemical biomarkers. A correlate does not make a surrogate. It is a common misconception ...
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