In addition to interferon-based therapies, a variety of other drugs for possible use in treating hepatitis B and C are in various stages of research or clinical trials.
Protease inhibitor therapy
A protease inhibitor would be any substance that partially or completely blocks the ability of an enzyme to carry out its activity. Protease inhibitors (similar to those used for HIV) are under investigation for hepatitis C patients who fail other treatments.
Ribozyme therapy or Heptazyme (Ribozyme Pharmaceuticals)
Ribozymes are RNA molecules that when directed against hepatitis C RNA have the ability to destroy the virus' replicative material. Preclinical studies have shown Heptazyme to have antiviral activity. Currently in phase 2 clinical trials for the treatment of chronic hepatitis C, Ribozyme therapy (Hepbzyme) may also offer a way to treat patients with hepatitis B virus that are resistant to conventional forms of therapy.
Colchicine is an alkaloid extracted from the bulb of the meadow saffron or Colchicum. It has been used for centuries as an anti-inflammatory agent in the treatment of gouty arthritis. Colchicine, a drug that inhibits collagen (a protein in the body the makes up scar tissue) has produced some improvement in liver function and survival. Colchicine can have severe side effects. Colchicine was combined with interferon in one clinical trial.
Albuferon (Human Genome Sciences)
Albuferon is created by fusing the gene for a human protein, interferon alpha, to the gene of another human protein, albumin. It currently is in phase 1 trials in hepatitis C patients.
Ursodeoxycholic acid or ursodiol or Actigall
One of the bile acids produced by the Chinese black bear, ursodiol has been used in the treatment of liver disease for centuries. It is now produced in the laboratory and is used in the treatment of gallstone disease. It is taken to dissolve the gallstones. It also has immune modulating factors. It is an approved drug that may limit liver injury and the effect of hepatitis C, although these uses are not included in product labeling. It is the standard drug used to treat primary biliary cirrhosis, but studies are questioning its effectiveness. It may be useful in combination with interferon.
Interleukin is the generic name for a group of proteins (cytokines) that are important in regulating inflammatory and immune responses. Some have specific anti-hepatitis C activity, and, therefore, have been studied as potential treatments for chronic hepatitis C. Studies have questioned their effectiveness, but scientists continue trying to develop interleukin compounds against hepatitis C.
Civacir is a human antibody product derived from screened donors. It contains antibodies that are neutralizing to hepatitis C virus. Nabi intends to develop the product for the prevention of hepatitis C reinfection of transplanted livers, post-exposure prophylaxis of hepatitis C, and ultimately for the treatment of certain stages of chronic hepatitis C infections.
Thymosin alpha 1 or thymalfasin or Zadaxin (SciClone)
Zadaxin is the synthetic version of thymosin alpha 1, originally isolated from the thymus gland. It stimulates the immune system and is able to act as an immunomodulator. Research indicates that it may be useful in treating a number of other diseases including hepatitis C. Thymosin alpha 1 has an excellent safety record with virtually no drug-related side effects.
For treatment of chronic hepatitis B or as a vaccine adjuvant, Zadaxin is approved for sale and available in 25 countries including China and Mexico.
For hepatitis C, Zadaxin has been most efficacious when used in combination with interferon and has shown significantly better results than interferon alone. Phase 3 trials in the U.S. and Europe are underway.
The internal ribosome initiation site (IRES) is a part of the hepatitis C virus that is found in different genotypes. It is an essential part of the replication process, so scientists believe that, by finding an IRES inhibitor, there will be a decreased production of the virus. Several companies are working with possible IRES inhibitors.
Antisense Based Therapies
Antisense inhibitor or ISIS 14803 (ISIS) is currently in phase 2 trials for hepatitis C.
HepDirect is a platform technology that enables the delivery of certain drugs to the liver with high specificity. The "HepDirect prodrug" will begin phase 1 trials in 2002 for treatment of hepatitis B.
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