Common brand names

• Pegasys

How it is administered

Pegylated interferon alfa-2a is administered as a subcutaneous injection, typically in the thigh or abdomen. It is available as a sterile, preservative-free solution in single-use vials or prefilled syringes. The standard adult dose is 180 mcg injected once weekly. Pediatric dosing is based on body surface area (180 mcg/1.73 m² × BSA, up to a maximum of 180 mcg), also given once weekly. The medication should be injected at the same time and day each week.

How it works

Pegylated interferon alfa-2a is a modified form of interferon, a protein that helps regulate the immune system. By attaching a polyethylene glycol (PEG) molecule, the medication stays in the body longer, allowing for once-weekly dosing. It works by binding to specific receptors on cell surfaces, triggering a cascade of signals inside cells (mainly through the JAK/STAT pathway). This leads to the production of proteins that help fight viruses and regulate immune responses.

In blood cancers, especially certain leukemias and lymphomas, interferons can slow the growth of cancer cells and enhance the body's immune response against them. While pegylated interferon alfa-2a is primarily approved for viral hepatitis, its immune-modulating effects are relevant in some blood cancers, where it can help control abnormal cell growth and support the immune system's ability to target cancer cells.

Who should take it

Pegylated interferon alfa-2a is FDA-approved for the treatment of chronic hepatitis B and C, including in patients with compensated liver disease. In blood cancer care, it may be used off-label for certain types of leukemia (such as hairy cell leukemia, chronic myeloid leukemia, and some lymphomas), especially when other treatments are not suitable or have failed.

Patients who may benefit include those with blood cancers where interferon therapy has shown effectiveness, or those who cannot tolerate standard chemotherapy. The decision to use this medication in blood cancer should be made by a hematologist or oncologist familiar with the patient's specific diagnosis and medical history.

Who should not take it

Pegylated interferon alfa-2a should not be used in patients with:

• Known hypersensitivity to interferons or any component of the product
• Autoimmune hepatitis
• Hepatic decompensation (advanced liver failure)
• Neonates and infants (due to risk from benzyl alcohol in the formulation)
• Severe psychiatric disorders, such as severe depression or suicidal ideation

It is also contraindicated in pregnancy when used with ribavirin, and caution is needed in patients with severe heart, kidney, or autoimmune diseases. Always discuss your full medical history with your healthcare provider before starting this medication.

Commonly used with

For hepatitis C, pegylated interferon alfa-2a is commonly used in combination with ribavirin and other antiviral medications. In blood cancer settings, it may be used alone or with other agents depending on the specific disease and patient needs.

If used off-label for blood cancers, it is sometimes combined with other chemotherapy or targeted therapies, but this should be managed by a specialist.

Commonly tested with

Pegylated interferon alfa-2a has been tested in combination with ribavirin for hepatitis C and with lamivudine for hepatitis B. In research and clinical trials for blood cancers, it may be studied with other chemotherapy agents or targeted therapies to assess combined effectiveness and safety.

If you are participating in a clinical trial, your healthcare team will provide specific information about any combination treatments being tested.