Mimrylo (Rusfertide)

Mimrylo (rusfertide) is a prescription medication approved by the U.S. Food and Drug Administration (FDA) to treat erythrocytosis (too many red blood cells) in adults with polycythemia vera (PV).

How Mimrylo Works and How It’s Taken

Mimrylo is a type of medicine called a hepcidin mimetic. It works like hepcidin, a hormone the body makes naturally. Mimrylo blocks a protein called ferroportin, which helps move iron in the body.

This lowers the amount of iron available to make red blood cells and helps lower hematocrit. Hematocrit is the percentage of your blood made up of red blood cells.

Doctors prescribe Mimrylo when adults with PV have erythrocytosis.

Mimrylo is given as an injection under the skin. With training from a healthcare provider, people or caregivers may give the injections at home.

Injection sites include the stomach area, the front of the thigh, or the outer upper arm. The outer upper arm should only be used when a caregiver gives the injection. Do not inject into the same spot twice in a row.

Typical Dosing for PV

The recommended starting dose of Mimrylo is 19 milligrams once a week. The recommended weekly dosage range is 9.5 milligrams to 108 milligrams.

If needed, your healthcare provider may increase your dose after you have been on your current weekly dose for at least two weeks. Dose increases may be used to reduce or keep your hematocrit below 45 percent.

Your healthcare provider may also lower your dose or stop treatment if certain side effects occur. Your healthcare provider will check your complete blood count every two to four weeks during dose changes, or as needed, to help make sure the dose remains safe and effective.

Weekly doses above 54 milligrams require two injections. If your weekly dose is greater than 82 milligrams, the first injection is given on day 1 and the second injection is given on day 4 or 5.

This information is based on prescribing information, but your healthcare provider may tailor your treatment plan. Always follow their guidance.

Mimrylo Side Effects

In a clinical study of Mimrylo in adults with PV, the most common side effects occurred in 16 percent to 56 percent of people. They included:

Injection site reactions (such as itching, pain, swelling, bruising, hardening, discoloration, or irritation)
Anemia (low red blood cell count)

Serious Side Effects and Warnings

Mimrylo has serious side effects and warnings, including:

New or worsening thrombocytosis (high platelet counts) — This can raise the risk of blood-clotting problems.
Embryo-fetal toxicity (potential harm to a fetus during pregnancy) — Mimrylo may cause fetal harm.

Get medical help right away if you think you are having a serious reaction.

How To Save on Mimrylo

Takeda Pharmaceuticals America, the manufacturer of Mimrylo, offers the Takeda Oncology Co-Pay Assistance Program. Eligible people with commercial insurance may pay as little as $0 per prescription.

The program is part of Takeda Oncology Here2Assist, which offers help working with your insurance company, filling and shipping prescriptions through a network of specialty pharmacies, and one-on-one nurse-led self-injection training with Nurse Navigators.

To learn more, visit the Mimrylo Patient Support page or call 844-817-6468.

What To Know Before Taking Mimrylo

Before starting Mimrylo and during dose changes, your doctor will check your complete blood count (CBC). This blood test checks your red blood cells, white blood cells, and platelets.

If you can become pregnant, your healthcare provider may do a pregnancy test before you start Mimrylo.

Tell your doctor if you have any allergies to Mimrylo or any of its ingredients.

Tell your doctor about all medicines you take, including prescription drugs, over-the-counter medicines, vitamins, and herbal supplements.

If you miss a dose, what you should do depends on your dosing schedule:

Once-weekly dosing, one to four days late — Take the missed injection as soon as you remember. Then return to your regular weekly schedule.
Once-weekly dosing, more than four days late — Take the missed injection as soon as you remember. Take your next injection three days later, then return to your regular weekly schedule.
Twice-weekly dosing, one to two days late — Take the missed injection as soon as you remember. Take your next injection three days later, then return to your regular schedule.
Twice-weekly dosing, more than two days late — Skip the missed injection and continue your regular schedule.

Mimrylo may harm a fetus during pregnancy. If you can become pregnant, use effective birth control during treatment and for at least 30 days after your final dose. Tell your healthcare provider right away if you become pregnant or think you may be pregnant, and stop taking Mimrylo if you become pregnant.

Do not breastfeed while taking Mimrylo or for 30 days after your final dose.

Community FAQs

These answers are fact-checked by our editorial staff.

How effective is Mimrylo for PV?

In a 32-week study of adults with PV, 76.9 percent of people taking Mimrylo met the study’s response goal between weeks 20 and 32. This meant they did not meet the study’s criteria for needing a phlebotomy, a procedure that removes some blood to help lower red blood cell levels. This compared with 32.9 percent of people taking a placebo (an inactive treatment).

People taking Mimrylo also needed fewer phlebotomies on average from the start of the study through week 32. The average was 0.53 with Mimrylo compared with 1.82 with placebo.

During the 32-week study, 62.6 percent of people taking Mimrylo maintained hematocrit below 45 percent, compared with 14.4 percent taking placebo. The study also found a greater average improvement in fatigue scores with Mimrylo at week 32.

When were effects seen in the Mimrylo study?

The study measured the main treatment response between weeks 20 and 32. It does not say exactly how long Mimrylo takes to start working.

From week 0 through week 32, average hematocrit stayed about the same or decreased in people taking Mimrylo, while it increased in the placebo group. When people in the placebo group switched to Mimrylo at week 32, their average hematocrit decreased rapidly.

What tests or monitoring are needed with Mimrylo for PV?

Your healthcare provider will check your complete blood count every two to four weeks after you start Mimrylo and during dose changes, or as needed.

These blood tests help check your platelet count and look for anemia. Mimrylo may increase platelet levels, and your dose may need to be changed if you develop anemia or certain serious side effects.