HEALTH-SYSTEM EDITION
CLINICAL PRACTICE

Meet Pegasys, a new drug to treat hepatitis C

Named after the winged horse in Greek mythology, Pegasus, Hoffmann-La Roche's new drug for hepatitis C, Pegasys, is a pegylated version of interferon alfa-2a. Pegylated, Gary C. Yee, Pharm.D., explained, means that polyethylene glycol (PEG) has been added to the molecule. By doing this, researchers increase both the water solubility of the drug and its clearance, thereby converting it into a longer-acting version of the drug.

Another advantage of pegylation, said Yee, who is professor and chair of the department of pharmacy practice at the University of Nebraska's College of Pharmacy, is it sometimes makes drugs less immunologic. That means patients may show less hypersensitivity to the pegylated version of a certain drug. Whether this is the case with interferon alfa-2a remains to be seen. According to prescribing information, such reactions "have been rarely observed during alpha interferon therapy."

PEG-Intron (interferon alfa-2b, Schering-Plough) is another pegylated version of interferon already on the market. It has been shown to be more effective than the conventional interferon alfa-2b in clinical studies, said Yee. This is unexpected because other pegylated drugs have not been much more effective than their nonpegylated counterparts.

Approved by the Food & Drug Administration in October, Pegasys has also proven to be better than its nonpegylated counterpart (interferon alfa-2a) in clinical trials. It has been tested and proven effective in hepatitis C patients, including patients with cirrhosis, and in patients with the most common form of hepatitis C, genotype 1.

Yee said it's hard to say what differences there will be between PEG-Intron and Pegasys. With the nonpegylated versions of both drugs, "most experts would say that they are similar and would be considered as therapeutically equivalent." It's not likely a head-to-head trial will ever be done, Yee continued, because the differences between the two drugs are likely to be very small. A large study would be needed to measure the differences, and it would be quite expensive.

One advantage Pegasys may have is availability. In order to receive PEG-Intron patients have to sign up with Schering and receive an identification number. Pharmacists must call Schering with this number every time they need to fill a PEG-Intron prescription for a patient. They will then receive another number to use when call- ing their wholesalers to receive a shipment of the drug. According to Pam Van Houten, a Roche spokeswoman, this will not be the case with Pegasys.

Also, Roche has teamed up with Priority Healthcare Corp. to distribute samples to physicians. Roche will be providing 12 weeks of Pegasys therapy for 15,000 patients. The 12-week supply was selected for a reason. During trials, researchers found that most patients who will have a positive response to Pegasys will demonstrate this by the 12-week point in therapy. At press time, Van Houten said, the sampling program was still open to new patients.

As with other interferon products, Pegasys carries significant warnings. The labeling warns that alpha interferon products may contribute to life-threatening or fatal disorders. These include autoimmune, ischemic, and neuropsychiatric disorders, as well as infections. Pegasys suppresses bone marrow function, and it may cause cardiac problems such as arrhythmias, myocardial infarction, and hypertension.

Pegasys interferes with endocrine function. It can cause or worsen both hyper- and hypothyroidism. It can do the same for blood sugar, resulting in hyper- and hypoglycemia, and some patients may develop diabetes.

Patients, physicians, and pharmacists can call 1-(877) PEGASYS for information about the product.

Jillene Magill-Lewis, R.Ph.

The author is a clinical writer in the Seattle area.

TIPS TO REMEMBER: Pegasys

• Pegasys is a subcutaneous injection dosed at 180 mcg (for most patients) once weekly, usually for 48 weeks. Doses should be adjusted for patients with renal impairment.

• Pegasys is contraindicated in infants and in patients with decompensated hepatic disease or autoimmune hepatitis.

• Pegasys should be used with extreme caution in patients with a history of depression.

• Blood cell counts should be obtained routinely, as Pegasys suppresses bone marrow function.

• In clinical studies, the most common side effects of Pegasys were fatigue, fever, nausea, headache, muscle and joint pain, and neutropenia. Hair loss, diarrhea, anorexia, dizziness, and depression were frequent also, occurring in more than 10% of study participants.

 

Jillene Lewis. Meet Pegasys, a new drug to treat hepatitis C. Drug Topics 2002;22:HSE8.