From the Guidelines
Sofosbuvir and ledipasvir are antiviral medications that work together to treat hepatitis C virus (HCV) infection by targeting the NS5B RNA-dependent RNA polymerase and NS5A protein of HCV, respectively.
Mechanism of Action
The mechanism of action of sofosbuvir involves inhibiting the NS5B RNA-dependent RNA polymerase of HCV, acting as a chain terminator when incorporated into the viral RNA, preventing further RNA synthesis and viral replication 1.
- Sofosbuvir is a prodrug that requires intracellular metabolism to form its active triphosphate metabolite.
- Ledipasvir works by inhibiting the NS5A protein of HCV, which is essential for viral RNA replication and assembly of virus particles.
Combination Therapy
The dual mechanism approach of targeting two different viral proteins simultaneously increases efficacy and reduces the risk of viral resistance, as seen in the ION-1, ION-2, ION-3, and ION-4 trials 1.
- These medications are often combined in a single tablet for the treatment of HCV genotype 1, 4, 5, and 6 infections.
- This combination therapy has revolutionized HCV treatment by providing a highly effective, well-tolerated, interferon-free regimen with cure rates exceeding 95% in most patient populations, as reported in the EASL recommendations on treatment of hepatitis C 2016 1.
Clinical Evidence
The EASL recommendations are based on the results of the four Phase III trials ION-1, ION-2, ION-3, and ION-4, which demonstrated high SVR12 rates in treatment-naive and treatment-experienced patients with or without compensated cirrhosis 1.
- The presence of NS5A RASs at baseline had no impact on SVR12 in treatment-naive patients, but was associated with a lower rate of SVR12 in treatment-experienced patients without cirrhosis treated for 12 weeks without ribavirin 1.
- The combination of sofosbuvir and ledipasvir has been shown to be effective in patients with compensated cirrhosis, with SVR12 rates of 95% after 12 weeks and 98% after 24 weeks of therapy 1.
From the FDA Drug Label
Ledipasvir is an HCV NS5A inhibitor and sofosbuvir is a nucleotide analog inhibitor of HCV NS5B polymerase. The mechanisms of sofosbuvir and ledipasvir are:
- Ledipasvir: inhibition of HCV NS5A
- Sofosbuvir: inhibition of HCV NS5B polymerase, which is a nucleotide analog inhibitor 2
From the Research
Mechanisms of Sofosbuvir and Ledipasvir
- Sofosbuvir is an NS5B polymerase inhibitor, which means it works by blocking the action of the NS5B protein that the hepatitis C virus (HCV) needs to replicate its genetic material 3.
- Ledipasvir is an NS5A inhibitor, which means it works by blocking the action of the NS5A protein that HCV needs to replicate and assemble new virus particles 3.
- The combination of sofosbuvir and ledipasvir has been shown to be highly effective in treating HCV genotype 1 infection, with sustained virologic response rates of approximately 96% in treatment-naive and -experienced patients 4, 5, 6, 7, 3.
Key Findings
- The fixed-dose combination of sofosbuvir and ledipasvir has been approved for the treatment of HCV genotype 1 infection, including an 8-week regimen for treatment-naive patients without cirrhosis and a baseline level of HCV RNA <6 million IU/mL 4, 3.
- The combination of sofosbuvir and ledipasvir has been shown to be effective in treating HCV genotype 1 infection in patients with and without cirrhosis, as well as in patients co-infected with HIV 6, 3.
- Factors associated with sustained virologic response failure include older age, presence of liver cirrhosis, diabetes, higher baseline viral load, and not achieving early virological response 7.