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Accession NumberDB05332

Romiplostim is a thrombopoiesis stimulating dimer Fc-peptide fusion protein (peptibody) to increase platelet production through activation of the thrombopoietin receptor. The peptibody molecule has two identical single-chain subunits, each one is made up of 269 amino acid residues. Each subunit consists of an IgG1 Fc carrier domain that is covalently attached to a polypeptide sequence that contains two binding domains to interact with thrombopoietin receptor c-Mpl. Each domain consists of 14 amino acids. Interestingly, romiplostim’s amino acid sequence is not similar to that of endogenous thrombopoietin. Romiplostim is produced by recombinant DNA technology in Escherichia coli. FDA approved on August 22, 2008.

Protein structureNo structure small
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Protein chemical formulaC2634H4086N722O790S18
Protein average weight59000.0 Da
>Thrombopoietin receptor binding domain amino acid sequence 
>Amino acid sequence for Fc fusion compound
Download FASTA Format
External Identifiers
  • AMG 531
Approved Prescription Products
NameDosageStrengthRouteLabellerMarketing StartMarketing End
Nplateinjection, powder, lyophilized, for solution250 ug/.5mLsubcutaneousAmgen Inc2008-08-25Not applicableUs
Nplatepowder for solution500 mcgsubcutaneousAmgen Canada Inc2009-04-15Not applicableCanada
Nplatepowder for solution250 mcgsubcutaneousAmgen Canada Inc2009-04-15Not applicableCanada
Nplateinjection, powder, lyophilized, for solution500 ug/mLsubcutaneousAmgen Inc2008-08-25Not applicableUs
Approved Generic Prescription ProductsNot Available
Approved Over the Counter ProductsNot Available
Unapproved/Other Products Not Available
International BrandsNot Available
Brand mixturesNot Available
SaltsNot Available
CAS number267639-76-9
DescriptionNot Available
KingdomOrganic Compounds
Super ClassOrganic Acids
ClassCarboxylic Acids and Derivatives
Sub ClassAmino Acids, Peptides, and Analogues
Direct ParentPeptides
Alternative ParentsNot Available
SubstituentsNot Available
Molecular FrameworkNot Available
External DescriptorsNot Available
IndicationTreatment of chronic immune thrombocytopenic purpura.
PharmacodynamicsResponses to platelet increase varies between patients thus indicating a need for individualization of dose. However, a dose dependent-increase in platelet counts have been observed in clinical trials. Does not affect platelet destruction.
Mechanism of actionRomiplostim is a thrombopoietin receptor agonist that activates intracellular transcriptional pathways via c-Mpl to increase production of platelets. It also works similarly to thrombopoietin (TPO), an endogenous glycoprotein hormone that regulates the production of platelets in the bone marrow.
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AbsorptionCmax, healthy volunteers, subQ = 24-36 hours; Cmax, immune thrombocytopenia patients, subQ = 7-50 hours (median = 14 hours). Not affected by age, weight, or gender. Accumulation does not occur after six weekly doses of 3 mcg/kg romiplostim.
Volume of distribution

In healthy volunteers, non-linear decrease in Vd with increase IV dose of romiplostim which indicates saturation of c-Mpl receptors.
Vd, 0.3 μg/kg = 122 mL/kg
Vd, 10 μg/kg = 48.2 mL/kg

Protein bindingNot Available
MetabolismNot Available
Route of eliminationRenal clearance (more dominant mode of clearance as dose increases) and binding to c-Mpl receptors (dominant mode of clearance at low doses)
Half lifeImmune thrombocytopenia patients, subQ = 3.5 days (median) (range 1-34 days)
ClearanceNot Available
ToxicityThe most common adverse reactions (≥ 5% higher patient incidence in Nplate versus placebo) are arthralgia, dizziness, insomnia, myalgia, pain in extremity, abdominal pain, shoulder pain, dyspepsia, and paresthesia. Headache was the most commonly reported adverse reaction that did not occur at ≥ 5% higher patient incidence in Nplate versus placebo. LD50 = 980 mg/kg.
Affected organisms
  • Humans and other mammals
PathwaysNot Available
SNP Mediated EffectsNot Available
SNP Mediated Adverse Drug ReactionsNot Available
ManufacturersNot Available
PackagersNot Available
Dosage forms
Injection, powder, lyophilized, for solutionsubcutaneous250 ug/.5mL
Injection, powder, lyophilized, for solutionsubcutaneous500 ug/mL
Powder for solutionsubcutaneous250 mcg
Powder for solutionsubcutaneous500 mcg
PricesNot Available
PatentsNot Available
Experimental PropertiesNot Available
Synthesis ReferenceNot Available
General References
  1. Kumagai Y, Fujita T, Ozaki M, Sahashi K, Ohkura M, Ohtsu T, Arai Y, Sonehara Y, Nichol JL: Pharmacodynamics and pharmacokinetics of AMG 531, a thrombopoiesis-stimulating peptibody, in healthy Japanese subjects: a randomized, placebo-controlled study. J Clin Pharmacol. 2007 Dec;47(12):1489-97. Epub 2007 Oct 9. [PubMed:17925591 ]
  2. Rice L: Drug evaluation: AMG-531 for the treatment of thrombocytopenias. Curr Opin Investig Drugs. 2006 Sep;7(9):834-41. [PubMed:17002262 ]
  3. Keating GM: Romiplostim: a review of its use in immune thrombocytopenia. Drugs. 2012 Feb 12;72(3):415-35. doi: 10.2165/11208260-000000000-00000. [PubMed:22316355 ]
  4. Link [Link]
External Links
ATC CodesB02BX04
AHFS CodesNot Available
PDB EntriesNot Available
FDA labelDownload (232 KB)
MSDSDownload (479 KB)
Drug InteractionsNo interactions found.
Food InteractionsNot Available


Pharmacological action
General Function:
Transmembrane signaling receptor activity
Specific Function:
Receptor for thrombopoietin. May represent a regulatory molecule specific for TPO-R-dependent immune responses.
Gene Name:
Uniprot ID:
Molecular Weight:
71244.08 Da
  1. Krzyzanski W, Sutjandra L, Perez-Ruixo JJ, Sloey B, Chow AT, Wang YM: Pharmacokinetic and pharmacodynamic modeling of romiplostim in animals. Pharm Res. 2013 Mar;30(3):655-69. doi: 10.1007/s11095-012-0894-2. Epub 2012 Dec 19. [PubMed:23250851 ]
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Drug created on November 18, 2007 11:23 / Updated on August 17, 2016 12:24