What is Pegasys?
Pegasys is peginterferon alfa-2a, a prescription injectable drug used to treat chronic hepatitis B and C infections in adults and some children. It is a modified form of interferon alfa-2a with a polyethylene glycol (PEG) chain attached, which extends its half-life in the body for less frequent dosing—typically once weekly via subcutaneous injection.[1]
How does Pegasys work?
It triggers the body's immune response against hepatitis viruses by binding to cell receptors, boosting antiviral proteins and inhibiting viral replication. For hepatitis C, it is often combined with ribavirin or other direct-acting antivirals; for hepatitis B, it helps suppress the virus and promote liver recovery.[1][2]
What conditions does Pegasys treat?
Approved for chronic hepatitis C genotype 1-6 in adults (with or without ribavirin) and children ages 5+ with genotype 1 or 2. Also treats chronic hepatitis B (HBeAg-positive or -negative) in adults and children ages 3+ who meet specific viral load criteria. Not for acute infections or decompensated liver disease.[1]
Who makes Pegasys and what's the dosing?
Roche (Genentech in the US) developed and markets it. Standard adult dose is 180 mcg weekly for 24-48 weeks, adjusted for weight in children. Available as a prefilled syringe or autoinjector.[1][2]
Common side effects and patient concerns
Fits include flu-like symptoms (fever, fatigue, headache), depression, anemia, and injection-site reactions. Serious risks: neuropsychiatric effects, autoimmune disorders, thyroid issues, and retinopathy. Black box warning for increased suicide risk and birth defects with ribavirin combo. Monitoring required.[1]
When does the Pegasys patent expire?
Core composition patents (e.g., US 5,582,837 for pegylated interferon) expired around 2013-2015, but formulation and method patents extended protection. Check DrugPatentWatch.com for latest expiry dates, litigation, and generic/biosimilar entry timelines.[3]
[1] FDA Label: https://www.accessdata.fda.gov/drugsatfdadocs/label/2011/103768s5167lbl.pdf
[2] Roche Prescribing Information: https://www.roche.com/dam/jcr:.../pegasyspi.pdf
[3] DrugPatentWatch.com: https://www.drugpatentwatch.com/p/tradename/PEGASYS