When Pegasys Isn't Available, What Are Your Options?

If you've been trying to fill a Pegasys (Peginterferon Alfa-2a) prescription and keep hearing "out of stock," you're not alone. The ongoing Pegasys shortage has left thousands of patients scrambling for alternatives.

The good news: depending on why you take Pegasys, there are real alternatives your doctor can consider. The right option depends on whether you're being treated for hepatitis B, hepatitis C, or a myeloproliferative blood disorder like polycythemia vera.

Let's break it down.

What Is Pegasys and How Does It Work?

Pegasys is the brand name for Peginterferon Alfa-2a, a pegylated interferon. It works by binding to interferon receptors on your cells and activating your immune system's natural antiviral and antiproliferative pathways. The "pegylated" part means it has a polyethylene glycol (PEG) chain attached, which slows down how fast your body breaks it down — allowing once-weekly dosing instead of multiple injections per week.

Pegasys is FDA-approved for chronic hepatitis B and hepatitis C, and it's widely used off-label for blood disorders like polycythemia vera (PV) and essential thrombocythemia (ET).

Alternatives for Polycythemia Vera and Essential Thrombocythemia

BESREMi (Ropeginterferon Alfa-2b)

BESREMi is the closest alternative to Pegasys for patients with polycythemia vera. It's another pegylated interferon, but it's a newer formulation (Ropeginterferon Alfa-2b) that is FDA-approved specifically for polycythemia vera in adults. The NCCN guidelines (Version 1.2025) explicitly recommend BESREMi as a substitute for patients affected by the Pegasys shortage.

Key differences from Pegasys:

• BESREMi is dosed every two weeks (vs. weekly for Pegasys) once stable
• It's FDA-approved for PV, while Pegasys is used off-label for this condition in the US
• Side effect profile is similar but may be better tolerated in some patients
• Cost is comparable — both are expensive specialty biologics

If you're on Pegasys for PV or ET, ask your hematologist about transitioning to BESREMi. Published guidance exists for how to switch between these medications safely.

Hydroxyurea

Hydroxyurea is an oral medication commonly used for polycythemia vera and essential thrombocythemia. It works differently from interferons — it directly reduces blood cell production in the bone marrow. While it's effective and much cheaper (often under $50/month), it's generally considered a different class of therapy and may not be appropriate for all patients, particularly younger patients or those seeking molecular remission.

Anagrelide (Agrylin)

For essential thrombocythemia specifically, Anagrelide is an option that reduces platelet counts. It's an oral medication taken daily. However, it doesn't reduce white blood cells or address the underlying disease biology the way interferons do.

Alternatives for Chronic Hepatitis C

If you were prescribed Pegasys for hepatitis C, the landscape has changed dramatically. Direct-acting antivirals (DAAs) have largely replaced interferon-based therapy and offer cure rates above 95% with far fewer side effects:

Harvoni (Ledipasvir/Sofosbuvir)

An oral tablet taken once daily for 8–12 weeks. Highly effective for hepatitis C genotypes 1, 4, 5, and 6. No injections needed.

Epclusa (Sofosbuvir/Velpatasvir)

A pan-genotypic oral treatment effective against all hepatitis C genotypes. Taken once daily for 12 weeks.

Mavyret (Glecaprevir/Pibrentasvir)

Another pan-genotypic option, taken as three tablets once daily for 8–16 weeks depending on treatment history. Often preferred for its shorter treatment duration.

For most hepatitis C patients today, these oral DAAs are actually preferred over Pegasys — they're more effective, better tolerated, and don't require weekly injections. Talk to your hepatologist or gastroenterologist about making the switch.

Alternatives for Chronic Hepatitis B

For hepatitis B, alternatives to Pegasys include:

• Entecavir (Baraclude) — an oral antiviral taken daily
• Tenofovir disoproxil (Viread) — another oral antiviral option
• Tenofovir alafenamide (Vemlidy) — a newer formulation with fewer kidney and bone side effects

These oral antivirals are effective at suppressing hepatitis B virus but typically require long-term (sometimes indefinite) treatment, unlike the finite course of Pegasys. Your doctor can help you weigh the pros and cons based on your specific situation.

Final Thoughts

Not being able to find your medication is stressful, but you have options. The right alternative depends entirely on your diagnosis and medical history — never switch medications on your own.

Talk to your doctor, and in the meantime, use Medfinder to check if Pegasys is available near you. The shortage is temporary, but your health can't wait.