Romiplostim belongs to a class of drugs called TPO (thrombopoietin) peptide mimetics. These drugs help your body to make more platelets, which are cells that help your blood to clot.

Romiplostim works by mimicking the action of your own natural TPO, which is a hormone produced by your liver and kidneys that regulates how many platelets you produce. Romiplostim binds to and activates the same receptors that your own endogenous TPO uses to increase platelet production. It is a TPO receptor agonist.

Romiplostim is a peptibody, which is a peptide fused to an antibody. It was the first fully engineered peptibody designed to stimulate platelet production and was approved by the US Food and Drug Administration (FDA) in 2008.

What is romiplostim used for?

• Romiplostim is a prescription medicine used to treat low blood platelet counts (thrombocytopenia) in:
  • adults with immune thrombocytopenia (ITP) when certain medicines or surgery to remove your spleen have not worked well enough.
  • children 1 year of age and older with ITP for at least 6 months when certain medicines or surgery to remove your spleen have not worked well enough.
• Romiplostim is a prescription medicine also used to treat people including newborns who have been exposed to high levels of radiation (acute radiation syndrome). The effectiveness of romiplostim for this use was only studied in animals, because it could not be studied in people.
• Romiplostim is not for use in people with a precancerous condition called myelodysplastic syndrome (MDS), or low platelet count caused by any condition other than ITP.
• Romiplostim is only used if your low platelet count and medical condition increase your risk of bleeding.
• Romiplostim is used to try to keep your platelet count about 50,000 per microliter in order to lower the risk for bleeding. romiplostim is not used to make your platelet count normal.
• It is not known if romiplostim is safe and effective in children under the age of 1.

Romiplostim can cause serious side effects, including:

• Worsening of a precancerous blood condition to a blood cancer (leukemia). Romiplostim is not for use in people with a precancerous condition called myelodysplastic syndromes (MDS), or for any condition other than immune thrombocytopenia (ITP). If you have MDS and receive romiplostim, your MDS condition may worsen and become an acute leukemia. If MDS worsens to become acute leukemia you may die sooner from the acute leukemia.
• Higher risk for blood clots.
  • You may have a higher risk of getting a blood clot if your platelet count becomes high during treatment with romiplostim. You may have severe complications or die from some forms of blood clots, such as clots that spread to the lungs or that cause heart attacks or strokes.
  • If you have a chronic liver disease, you may get blood clots in the veins of your liver. This may affect your liver function.
• Injection of too much romiplostim may cause a dangerous increase in your blood platelet count and serious side effects. Your healthcare provider may change your dose or stop romiplostim depending upon the change in your blood platelet count. You must have blood platelet counts done before you start, during, and after romiplostim therapy is stopped (see “How should I receive romiplostim?” below).

See “What are the side effects of romiplostim?” below for other side effects of romiplostim.

• Romiplostim for ITP is given by your healthcare provider as an injection under the skin (subcutaneous) one time each week.
• Romiplostim is given by your healthcare provider as an injection under the skin once for exposure to high levels of radiation.
• During treatment for ITP, your healthcare provider will closely monitor your romiplostim dose and platelet counts.
  • Your healthcare provider will check your platelet count every week and change your dose of romiplostim as needed. This will continue until your healthcare provider decides that your dose of romiplostim can stay the same. After that, you will need to get blood tests every month. When you stop receiving romiplostim, you will need blood tests for at least 2 weeks to check if your platelet count drops too low.
  • Tell your healthcare provider about any bruising or bleeding that occurs during treatment with romiplostim.

• In patients with ITP the recommended initial dose of romiplostim is 1 mcg/kg once weekly as a subcutaneous injection. The dose should be adjusted based on platelet response.
• In patients acutely exposed to myelosuppressive doses of radiation the recommended dose of romiplostim is 10 mcg/kg administered once as a subcutaneous injection. The dose should be administered as soon as possible after suspected or confirmed exposure to myelosuppressive doses of radiation.
• See Full Prescribing Information for instructions on reconstitution, preparation, and administration.

Before receiving romiplostim, first speak to your healthcare provider and understand the benefits and risks of romiplostim. Be sure to tell your healthcare provider about all of your medical conditions, including if you:

• have had surgery to remove your spleen (splenectomy)
• have a bone marrow problem, including a blood cancer or MDS
• have or had a blood clot
• have chronic liver disease
• have bleeding problems

If you miss a scheduled dose of romiplostim, call your healthcare provider to schedule your next dose as soon as possible.

Avoid situations or medicines that may increase your risk of bleeding.

Romiplostim may cause serious side effects.

See “Important information” above.

The most common side effects of romiplostim in adults include:

• headache
• tingling or numbness in hands and feet
• joint pain
• bronchitis
• dizziness
• inflammation of the sinuses (sinusitis)
• trouble sleeping
• vomiting
• muscle tenderness or weakness
• pain in the arms and legs
• stomach (abdomen) pain
• shoulder pain
• indigestion
• diarrhea
• upper respiratory tract infection
• cough
• nausea
• pain in mouth and throat (oropharyngeal pain)

The most common side effects of romiplostim in children 1 year of age and older include:

• bruising
• upper respiratory tract infection
• pain in mouth and throat (oropharyngeal pain)

People who take romiplostim may have an increased risk of developing new or worsening changes in the bone marrow called “increased reticulin”. These changes may improve if you stop taking romiplostim. Your healthcare provider may need to check your bone marrow for this problem during treatment with romiplostim.

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

You may also report side effects to Amgen at 1-800-77-AMGEN (1-800-772-6436).

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal products.

Know the medicines you take. Keep a list of them and show it to your healthcare provider or pharmacist when you get a new medicine.