How Does It Work?Pegasys is a manufactured version of interferon and is almost identical to a naturally occurring human interferon. Interferons are naturally occurring proteins or glycoproteins (proteins attached to carbohydrates). In humans, interferons are produced by cells in response to certain situations, such as viral infections, and often play a key role in the immune system.
When given as medications, interferons do not last very long in the body. To get around this problem, Pegasys was made by attaching each interferon to a molecule of polyethylene glycol. This makes the medication last much longer, allowing for once-a-week dosing. Because Pegasys is a protein, it would be broken down and destroyed by the digestive system if taken by mouth. For this reason, the drug must be injected to bypass the digestive tract.
Pegasys works to fight hepatitis B and C by activating the body's own response to viruses.