The Food and Drug Administration (FDA) today approved Tyzeka
(telbivudine) for the treatment of adults with chronic hepatitis B (HBV), a
serious viral infection that attacks the liver and can cause lifelong infection,
scarring of the liver (cirrhosis), and eventually liver cancer, liver failure,
and death. Tyzeka is a new molecular entity, which is a term used by the FDA to
describe a medication containing an active substance that has never before been
approved for marketing in any form in the United States.
“In a typical year, an estimated 70,000 Americans become infected with
chronic HBV, and some 5,000 of them will die of the complications caused by the
disease,” said Dr. Steven Galson, Director of the Center for Drug Evaluation and
Research. “Tyzeka offers prescribers another option for treating these
patients.”
Tyzeka was studied in a year-long international clinical trial in 1,367
patients with chronic HBV. Three-quarters of the trial participants were male,
and all were 16 years of age or older. The trial produced evidence of antiviral
effectiveness, including the suppression of hepatitis B virus, and improvement
in liver inflammation comparable to Epivir-HBV (lamivudine), one of five other
medications approved to treat patients with chronic HBV.
HBV is spread when blood from an infected person enters the body of a
person who is not infected, sometimes by sexual contact or blood contamination.
Tyzeka is not a cure for hepatitis B, and long-term treatment benefits of this
drug are not known. Use of Tyzeka has not been shown to reduce the risk of
transmission of HBV to others through sexual contact or blood
contamination.
In
clinical studies Tyzeka was generally well tolerated, and most reported adverse
events were mild to moderate. The most common side effects were elevated CPK
(creatinine phosphokinase, an enzyme that is present in muscle tissue and is a
marker for breakdown of muscle tissue), upper respiratory tract infection,
fatigue, headache, abdominal pain and cough.
Also, after several weeks to months of Tyzeka use, some patients
developed symptoms ranging from transient muscle pain to muscle weakness. Those
who developed muscle weakness experienced significant improvement in their
symptoms when Tyzeka was discontinued.
Patients should only stop Tyzeka after a careful discussion with their
doctor. As has happened with other forms of treatment for hepatitis B, some
patients who discontinued Tyzeka experienced a sudden and severe worsening of
their hepatitis B. Therefore, patients who discontinue Tyzeka should be closely
monitored by their doctor for at least several months.
Among drugs in the same class as Tyzeka, some cases of lactic acidosis
(too much acid in the body due to buildup of lactic acid) and severe enlargement
and accumulation of fat in the liver, including fatal cases, have been
reported.
Tyzeka is manufactured by Novartis Pharma
Stein AG, Stein, Switzerland and marketed and distributed by Idenix
Pharmaceuticals, Inc., Cambridge, MA.
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