Idenix Pharmaceuticals and Novartis Pharmaceuticals' Tyzeka

Monica Holmberg, PharmD
Published Online: Thursday, February 1, 2007

The FDA has approved Tyzeka (telbivudine) for the treatment of chronic hepatitis B in adults. Tyzeka will be available as a once-a-day regimen to be taken orally without regard to food or meals.1 Tyzeka is marketed by Idenix Pharmaceuticals Inc and Novartis Pharmaceuticals.2

Liver cancer is the fifth most frequent cancer worldwide, and ~80% of primary liver cancer is associated with hepatitis B virus (HBV). Approximately 1.25 million Americans currently have HBV.3 An estimated 70,000 more Americans will become infected each year, and 5000 will die from HBV complications.4 Worldwide, about 350 million people are infected with HBV.3

Patients infected with HBV may have nonspecific symptoms, such as jaundice, fatigue, abdominal pain, loss of appetite, nausea, vomiting, and joint pain. Sometimes HBV presents without any symptoms at all. Because the physical manifestations of the disease may be vague, patients may be unaware that they are infected with HBV, putting themselves at risk for disease progression and complications and putting others at risk for catching the disease.3 HBV is transmitted through blood.4

HBV can be prevented with immunization. Although HBV cannot be cured, new treatment regimens aim to improve response rates, provide long-term efficacy, reduce drug resistance, improve safety and tolerability, and provide a convenient route of administration.3

Clinical Trials

Tyzeka was compared with lamivudine in a clinical trial involving 1367 patients. Therapeutic response was evaluated by an end point of viral suppression. Viral suppression was measured by serum HBV DNA suppression below 100,000 copies/mL, along with either an improvement in liver disease markers, such as alanine aminotransferase normalization, or loss of detectable hepatitis B e-antigen (HbeAg).

At the end of 1 year of treatment, 75% of HbeAg-positive patients using Tyzeka achieved therapeutic response, compared with 67% of the lamivudine group.

Similar efficacy rates were noted in the HbeAg-negative group; 75% of Tyzeka patients and 77% of lamivudine patients responded.1

Additional results from the study showed therapeutic response after 2 years. In patients who were initially HbeAg-positive, 56% of the Tyzeka group had undetectable levels, compared with 39% of the lamivudine group, and 82% of Tyzeka patients who were initially HbeAg-negative achieved undetectable virus levels and 57% of the lamivudine group responded. It was noted that the antiviral response at 24 weeks was associated with better clinical outcomes after 2 years.5

Dosage

Tyzeka will be available as 600-mg once-daily tablets. Dose adjustments are necessary in patients with creatinine clearance (CrCl) less than 50 mL/min. Patients with CrCl between 30 and 49 mL/min should receive 600 mg every 48 hours, and patients with CrCl less than 30 mL/min should receive 600 mg every 72 hours. In patients receiving hemodialysis, the 600-mg dose should be administered every 96 hours after hemodialysis.2

Safety

Lactic acidosis and severe hepatomegaly with steatosis have been reported in patients using nucleoside analogues with or without retroviral agents. As with other HBV therapies, some patients may experience an acute exacerbation of hepatitis B on discontinuation of therapy. Close monitoring of liver function is recommended for several months after stopping treatment with Tyzeka.

Myopathy has been reported weeks to months after initiating therapy with Tyzeka. Patients experiencing muscle pain or weakness should contact their prescriber immediately.

Tyzeka is eliminated renally; the dose should be adjusted appropriately in patients with CrCl less than 50 mL/min. Tyzeka is not approved for use in pediatric patients. In clinical trials, 9% of patients using Tyzeka had grade 3/4 creatine kinase elevations.

Tyzeka is not a cure for HBV, nor will it prevent the transmission of the virus.1 The most common side effects included creatine phosphokinase elevation, upper respiratory tract infection, fatigue, headache, abdominal pain, and cough.4

Dr. Holmberg is a pharmacist with Phoenix Children's Hospital, Phoenix, Ariz.


References

1. Press Release: TYZEKA (telbivudine) approved in the U.S. as a new treatment for patients with chronic hepatitis B. Available at: www.pharma.us.novartis.com/newsroom/pressReleases/releaseDetail.jsp?PRID=2005. Accessed December 2006.

2. Waknine Y. FDA Approvals: Tyzeka and Humira. Available at: www.medscape.com/viewarticle/548958. Accessed December 2006.

3. Hepatitis B. Available at: www.idenix.com/markets/hbv.html. Accessed December 2006.

4. FDA approves new treatment for chronic hepatitis B in adults. Available at: www.fda.gov/bbs/topics/NEWS/2006/NEW01498.html. Accessed December 2006.

5. Press Release: New telbivudine data from three clinical trials to be presented this week at the American Association for the Study of Liver Diseases (AASLD). Available at: www.pharma.us.novartis.com/newsroom/pressReleases/releaseDetail.jsp?PRID=2006. Accessed December 2006.




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