Besremi Is a Prescription Interferon Injection Used to Treat Polycythemia Vera in Adults

Besremi (Ropeginterferon Alfa-2b-njft) is the only FDA-approved interferon specifically designed to treat polycythemia vera (PV), a rare blood cancer where your body makes too many red blood cells. It was approved by the FDA in November 2021 and is manufactured by PharmaEssentia Corporation.

If you've recently been prescribed Besremi or are researching treatment options for PV, this guide covers everything you need to know — from what it's used for to how it's taken, who shouldn't take it, and how much it costs.

What Is Besremi?

Here are the key facts:

• Brand name: Besremi (also written as BESREMi)
• Generic name: Ropeginterferon Alfa-2b-njft
• Drug class: Pegylated Interferon Alfa-2b
• Manufacturer: PharmaEssentia Corporation
• FDA approval: November 2021
• Controlled substance: No
• Form: 500 mcg/mL solution in a prefilled syringe for subcutaneous injection

Besremi belongs to a class of medications called interferons. These are proteins that your body naturally produces to fight infections and regulate your immune system. Besremi is a synthetic, long-acting (pegylated) version that's been engineered specifically for treating PV. For more on how it works at the cellular level, read our mechanism of action guide.

What Is Besremi Used For?

FDA-Approved Use: Polycythemia Vera

Besremi is approved to treat polycythemia vera in adults. PV is a myeloproliferative neoplasm — a type of slow-growing blood cancer driven by a mutation in the JAK2 gene (present in about 95% of PV patients). In PV, your bone marrow makes too many red blood cells, which thickens your blood and increases the risk of dangerous blood clots, stroke, and heart attack.

Besremi helps by:

• Reducing red blood cell, white blood cell, and platelet counts
• Targeting and reducing the JAK2 mutant clone — the abnormal cells driving the disease
• Lowering the risk of blood clots and other PV complications

Off-Label Use

Some doctors also use Besremi off-label for essential thrombocythemia (ET), another myeloproliferative neoplasm. The NCCN guidelines include it as a Category 1 preferred regimen for ET, and FDA review for this indication is ongoing.

How Is Besremi Taken?

Besremi is a self-administered subcutaneous injection given every two weeks. Here's what the dosing schedule looks like:

• Starting dose: 100 mcg every two weeks (or 50 mcg if you're transitioning from Hydroxyurea)
• Dose titration: Your doctor increases the dose by 50 mcg increments every two weeks, based on your blood counts
• Maximum dose: 500 mcg every two weeks
• Injection sites: Abdomen, thigh, or upper arm — rotate sites with each injection

The medication comes in a prefilled syringe and must be stored in the refrigerator. Your doctor's office or specialty pharmacy will train you on how to give yourself the injection. Most patients find it becomes routine after a few doses.

Important Dosing Notes

• Your dose is individualized based on your blood work. There's no one-size-fits-all dose.
• Blood work is typically done every 2-4 weeks during dose titration, then less frequently once you're stable.
• Don't change your dose without talking to your doctor.
• If you miss a dose, contact your doctor for instructions.

Who Should Not Take Besremi?

Besremi is not appropriate for everyone. You should not take Besremi if you have:

• A history of severe psychiatric disorders, especially depression or suicidal ideation
• Serious or untreated autoimmune disease
• An allergy to interferon or any ingredient in Besremi
• Decompensated liver disease
• An organ transplant requiring immunosuppressive therapy
• Uncontrolled high blood pressure
• Congestive heart failure
• Serious abnormal heart rhythm
• Severe coronary artery disease
• Recent stroke or heart attack

Besremi is also contraindicated in pregnancy. Women must use effective birth control during treatment and for at least 8 weeks after the last dose.

For a complete list of side effects and warnings, see our Besremi side effects guide.

How Much Does Besremi Cost?

Without insurance, Besremi costs approximately $9,700 to $11,000 per injection (per 1 mL prefilled syringe). Since it's given every two weeks, the annual cost can exceed $250,000 at cash price.

However, most patients don't pay anything close to that:

• Commercial insurance: Most plans cover Besremi with prior authorization. The PharmaEssentia SOURCE Copay Assistance Program can reduce your out-of-pocket cost to as little as $0 per month. Enroll at BESREMiCopay.com.
• Medicare and Medicaid: Coverage is available but copay assistance programs are not (federal law prohibits it). The PharmaEssentia SOURCE Patient Assistance Program may help if you're underinsured.
• Uninsured patients: The PharmaEssentia SOURCE Patient Assistance Program (PAP) provides Besremi at no cost to eligible patients. Call 1-833-546-7473 to apply.

There is currently no generic version of Besremi available.

How Does Besremi Compare to Other PV Treatments?

Besremi isn't the only option for PV. Here's how it stacks up against the main alternatives:

• Hydroxyurea (Hydrea, Droxia) — The most commonly used first-line treatment. Taken as a daily oral capsule. Much less expensive but carries a small long-term risk of leukemia transformation and requires ongoing monitoring.
• Ruxolitinib (Jakafi) — An oral JAK inhibitor approved for PV patients who don't respond to or can't tolerate Hydroxyurea. Effective for symptom control and spleen reduction.
• Pegasys (Peginterferon Alfa-2a) — Another interferon used off-label for PV, but it's been in shortage since 2024. Besremi is now the preferred interferon option per NCCN guidelines.

Besremi's main advantages are its ability to reduce the JAK2 mutant clone burden (potentially modifying the disease course) and its convenient every-two-week dosing schedule.

Final Thoughts

Besremi represents a significant advance in PV treatment. It's the first interferon specifically approved for the condition, and its ability to target the underlying JAK2 mutation sets it apart from older treatments. While the injection schedule and specialty pharmacy process take some getting used to, most patients find it manageable — and the clinical benefits can be substantial.

If you're considering Besremi, talk to your hematologist about whether it's right for your specific situation. And if you've already been prescribed it, make sure you're enrolled in the copay assistance program to keep costs down.

Need help finding Besremi? Search on Medfinder to check pharmacy availability near you.