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Nplate (Romiplostim) 250mkg.jpg
Trade namesNplate, Romiplate
Other namesAMG531
  • L-methionyl[human immunogloblin heavy constant gamma 1-(227 C-terminal residues)-peptide (Fc fragment)] fusion protein with 41 amino acids peptide, (7-7′:10,10′)-bisdisulfide dimer
Clinical data
Drug classColony-stimulating factor[1]
Main usesImmune thrombocytopenic purpura (ITP), acute radiation syndrome[1][2]
Side effectsJoint pain, trouble sleeping, abdominal pain, headache, tiredness[1]
  • AU: B3
Routes of
External links
License data
Legal status
  • AU: S4 (Prescription only)
  • US: ℞-only
  • EU: Rx-only
Elimination half-life1 to 34 days
Chemical and physical data
Molar mass59085.01 g·mol−1

Romiplostim, sold under the brand name Nplate among others, is a medication used to treat immune thrombocytopenic purpura (ITP) and acute radiation syndrome.[1][2] In ITP it may be used when corticosteroids, immunoglobulins, or splenectomy are not effective.[2] It is given by injection under the skin.[2]

Common side effects include joint pain, trouble sleeping, abdominal pain, headache, and tiredness.[1] Other side effects include blood cancer, blood clots, and bone marrow fibrosis.[1] Safety in pregnancy is unclear.[3] It works to stimulate platelet production by activating the thrombopoietin receptor.[4]

Romiplostim was approved for medical use in the United States in 2008 and Europe in 2009.[4][1] In the United Kingdom a 125 mcg vial costs the NHS about £240 as of 2021.[5] This amount in the United States costs about 1,100 USD.[6]

Medical uses

Romiplostim is indicated as a potential treatment for chronic idiopathic (immune) thrombocytopenic purpura (ITP).[7] Romiplostim was designated an orphan drug by the U.S. Food and Drug Administration (FDA) in 2003, as the chronic ITP population in the USA is under 200,000 (the chronic adult ITP population in the USA is thought to be around 60,000, with women outnumbering men by a factor of two).[8] The wholesale cost of romiplostim if administered weekly is currently estimated at US$55,250 per year.[9]

On August 22, 2008, the FDA approved romiplostim as a long-term treatment for chronic ITP in adults who have not responded to other treatments, such as corticosteroids, intravenous immunoglobulin, Rho(D) immune globulin or splenectomy.[10][11]


In a, 24-week, Phase III trials, romiplostim was more effective than placebo in achieving the primary endpoint of a durable platelet response in nonsplenectomized or splenectomized adults with chronic immune thrombocytopenic purpura.[12]


Romiplostim treatment is generally administered at weekly intervals via subcutaneous injection.[2] Often an initial dose of 1 mcg/kg is used for ITP.[2][5] For radiation sickness a dose of 10 mcg/kg may be used.[2]

Prior to injection, a complete blood count (CBC) is obtained, as the dosage is dependent on the individual's body weight and platelet count at the time of treatment. The goal of treatment is to maintain the count above 50,000 per cubic millimeter (mm3) of blood, not to achieve a normal count—defined as 150,000–450,000 per mm3 in most healthy individuals. If a count of 200,000 or higher is achieved for two consecutive weeks a reduced dose is administered or treatment is suspended until the count decreases below 200,000. Discontinuation of romiplostim must be approached with great caution, as a rapid decrease in the platelet count may occur, possibly leading to bleeding diathesis.

Side effects

Romiplostim's effect is to stimulate the patient's megakaryocytes to produce platelets at a more rapid than normal rate, thus overwhelming the immune system's ability to destroy them. As doing so involves changes to the bone marrow chemistry, a number of potentially serious side-effects may develop, including death, myalgia, joint and extremity discomfort, insomnia, thrombocytosis, which may lead to potentially fatal clots, and bone marrow fibrosis, the latter of which may result in an unsafe decrease in the red blood count.


The drug was developed by Amgen through a restricted usage program called NEXUS.[10] During development and clinical trials the drug was called AMG531.


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 "Romiplostim Monograph for Professionals". Archived from the original on 16 September 2021. Retrieved 18 October 2021.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 "DailyMed - NPLATE- romiplostim injection, powder, lyophilized, for solution". Archived from the original on 16 September 2021. Retrieved 18 October 2021.
  3. "Romiplostim (Nplate) Use During Pregnancy". Archived from the original on 4 December 2020. Retrieved 18 October 2021.
  4. 4.0 4.1 "Nplate". Archived from the original on 3 March 2021. Retrieved 18 October 2021.
  5. 5.0 5.1 BNF (80 ed.). BMJ Group and the Pharmaceutical Press. September 2020 – March 2021. p. 1096. ISBN 978-0-85711-369-6.
  6. "Nplate Prices, Coupons & Patient Assistance Programs". Retrieved 18 October 2021.
  7. Kuter DJ, Bussel JB, Lyons RM, et al. (February 2008). "Efficacy of romiplostim in patients with chronic immune thrombocytopenic purpura: a double-blind randomised controlled trial". Lancet. 371 (9610): 395–403. doi:10.1016/S0140-6736(08)60203-2. PMID 18242413. S2CID 23827197.
  8. "Amgen to Discuss Romiplostim BLA". 12 March 2008. Archived from the original on 3 March 2016. Retrieved 4 November 2008.
  9. Perreault, S; Burzynski, J (2009). "Romiplostim: a novel thrombopoiesis-stimulating agent". Am J Health Syst Pharm. 66 (9): 817–24. doi:10.2146/ajhp080524. PMID 19386944.
  10. 10.0 10.1 Waknine, Yael (4 September 2008). "FDA Approvals: Nplate, Aloxi, Vidaza". Medscape. Archived from the original on 2 December 2008. Retrieved 4 September 2008. Freely available with registration.
  11. "FDA Approves Nplate(TM) for Long-Term Treatment of Adult Chronic ITP" (Press release). Amgen. 22 August 2008. Archived from the original on 15 September 2008. Retrieved 4 September 2008.
  12. Frampton J. E., Lyseng-Williamson K. A. (2009). "Romiplostim". Drugs. 69 (3): 307–317. doi:10.2165/00003495-200969030-00006. PMID 19275274.

External links

External sites: