New Hepatitis C Treatments (cont.)
Melissa Conrad Stöppler, MD
Melissa Conrad Stöppler, MD
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
There have been several problems with combination treatment with interferon and ribavirin. Treatment is effective in no more than 50% of patients who are eligible for treatment, and many patients have not been eligible for treatment due to concerns about side effects. There are many subgroups of patients for whom treatment is not very effective, for example, patients with cirrhosis. Both interferon and ribavirin target systems in the body that are important to everyday health--the immune system and the production of new cells (which is the same system that hepatitis C virus uses to reproduce in the body). As a result, serious, even life-threatening side effects have occurred with treatment. Finally, treatment frequently has required 24 to 48 weeks.
The types of drugs available for treating chronic hepatitis C virus are undergoing a radical change. The genetic material of hepatitis C virus (its RNA) has been sequenced, and most of the virus' genes are now known. Some genes direct the manufacture of enzymes that are crucial to the production of new hepatitis C virus. Others are crucial for production of new hepatitis C virus, but their exact functions are unknown. Knowing the nature of the hepatitis C virus genetic material and its products, it has been possible to develop drugs that target portions of the genetic material or its products and prevent their actions. These drugs are referred to as direct acting anti-viral drugs. The newer drugs target systems that are unique to hepatitis C virus, in contrast to interferon and ribavirin that target systems that are important to everyday health as well as to production of new hepatitis C virus. This shift in focus of treatment to systems that are necessary for survival of the virus, but unimportant to patients results in fewer side effects. In addition, it turns out that the direct acting antiviral drugs are much more effective in eradicating hepatitis C virus - in upwards of 85% of patients - in even those patients who have had poor responses to interferon and ribavirin. There are also hints that treatment is likely to be shorter.
Drugs for treating hepatitis C of a second type, referred to as host-targeted agents, also are being developed. These drugs target proteins that are part of healthy liver cells' machinery but are used by hepatitis C virus to survive and reproduce. It is possible to prevent the virus from using the liver cells' machinery without seriously affecting the health of the liver cell.
The first of the new, direct acting antiviral drugs - telaprevir (Incivek) and boceprevir (Victrelis) - still are used in combination with interferon and ribavirin. The exciting news is that drugs even newer than telaprevir and boceprevir are being approved for use that eliminate the need for interferon and, in some cases, ribavirin. Ultimately, they likely will be used as combinations of two or even three direct acting drugs without interferon or ribavirin. This eliminates the side effects of interferon and ribavirin. In addition, by using several drugs that act by blocking different parts of the hepatitis C virus genetic material or the liver cells' machinery, the combinations become more effective, and the development of resistance to any one drug is reduced. Approved drugs of the new class of direct acting antivirals include simeprevir (Olysio) and sofosbuvir (Sovaldi).
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