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Information about Sofosbuvir
Sofosbuvir is an oral nucleoside analogue and potent inhibitor of the hepatitis C virus (HCV) RNA polymerase that is used in combination with other antiviral agents to treat chronic hepatitis C. Elevations in serum enzyme levels during sofosbuvir therapy are uncommon, and it has not been implicated convincingly in cases of clinically apparent liver injury with jaundice. Nevertheless, and for unknown reasons, successful antiviral therapy of hepatitis C with sofosbuvir and other direct acting agents in patients with cirrhosis is occasionally complicated by hepatic decompensation; furthermore, treatment can cause reactivation of hepatitis B in susceptible patients coinfected with the hepatitis B virus (HBV).
Mechanism of action of Sofosbuvir
Sofosbuvir (soe fos' bue vir) is an orally available nucleotide analogue that has potent activity against the RNA-dependent RNA polymerase of the hepatitis C virus (HCV). Sofosbuvir is a monophosphorylated uracil derivative whose single phosphate is protected by an alaninate cap that allows for the absorption and uptake of the molecule by hepatocytes where it is hydrolyzed to sofosbuvir monophosphate. Intracellular host kinases then convert it to the active triphosphate moiety. In multiple clinical trials, sofosbuvir has been shown to cause a rapid and marked decline in serum HCV RNA levels and, in combination with other antiviral agents and with more prolonged therapy, to result in sustained clearance of HCV (sustained virological response: SVR) in a high proportion of patients.
FDA approval information for Sofosbuvir
Sofosbuvir was approved for use in the United States in 2013 to be used in combination with ribavirin or with both peginterferon and ribavirin in patients with chronic hepatitis C, genotypes 1, 2, 3 or 4. Sofosbuvir is available in tablets of 400 mg under the brand name Solvaldi, the recommended dose being 400 mg once daily in combination with either ribavirin alone (1000 or 1200 mg daily for 12 weeks for genotype 2 and 24 weeks for genotype 3) or in combination with both ribavirin and peginterferon for 12 weeks for patients with genotype 1.
Subsequently, a fixed combination of sofosbuvir (400 mg) and the HCV NS5A replication complex inhibitor ledipasvir (le dip' as vir: 90 mg) was approved for use in patients with chronic hepatitis C, genotype 1 in 2014 and for genotype 4 in 2015. This combination is available as a fixed dose, single tablet under the brand name Harvoni and the recommended dose is one tablet daily for 12 weeks, which can be shortened to 8 weeks in selected patients.
In addition, sofosbuvir combined with NS5A inhibitors with broader activity against HCV genotypes, daclatasvir [dak lat' as vir: 2015] and velpatasvir [vel pat' as vir: 2016], has been shown to be effective in treating almost all HCV genotypes with sustained response rates of 95% or greater in response to 12 weeks of treatment in genotypes 1, 2, 4, 5 and 6. In 2016, the fixed combination of sofosbuvir (400 mg) and velpatasvir (100 mg) was approved for use in patients with all 6 genotypes of hepatitis C. This combination is available as a fixed dose, single tablet under the brand name Epclusa. The recommended dose is one tablet daily for 12 weeks. For patients with decompensated cirrhosis (Childs-Pugh Class B or C), ribavirin (1000 to 1200 mg in two divided doses daily) should be added to Epclusa for 12 weeks. Finally, the combination of sofosbuvir with an HCV specific NS3/4 protease inhibitor (such as simeprevir ) was also shown to be highly effective in patients with genotype 1 infection generally in 12 week courses.
FDA approval information for Sofosbuvir
For patients who fail to respond to a two or three drug combination of direct acting antiviral agents, combinations of potent agents active against the three major HCV poiypeptide products have been developed and have shown excellent activity in these refractory patients. The first such regimen was a single tablet formulation of sofosbuvir (400 mg), velpatasvir (100 mg) and a potent, broad spectrum (pangenomic) HCV protease inhibitor, voxilaprevir (100 mg).
This combination was approved for use in the United States in 2017 and is available under the brand name Vosevi. The recommended dosing regimen is 1 tablet daily for 12 weeks. This regimen is not recommended for patients with decompensated cirrhosis (Childs-Pugh Class B or C).
As such, sofosbuvir transformed the therapy of chronic hepatitis C and became the most commonly used HCV-specific antiviral agent, replacing peginterferon and combinations of peginterferon, ribavirin and protease inhibitors. Sofosbuvir has few side effects and in placebo controlled trials adverse events occurred at a similar rate with sofosbuvir as placebo.
Side effects of Sofosbuvir
The following are drugs for Hepatitis C:
HCV NS5A Inhibitors
HCV NS5B (Polymerase) Inhibitors
HCV Protease Inhibitors
- Asunaprevir, Boceprevir, Glecaprevir, Grazoprevir, Paritaprevir, Simeprevir, Telaprevir, Voxilaprevir