Nplate is the trade name for Romiplostim (rINN, USAN) which is a fusion protein analogue of thrombopoietin, a hormone that regulates platelet production. The drug was developed by Amgen and is marketed under the trade name Nplate through a restricted usage program called NEXUS. During development and clinical trials, the drug was called AMG531.
Romiplostim is indicated as a potential treatment for chronic idiopathic (immune) thrombocytopenic purpura (ITP). 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). The wholesale cost of romiplostim if administered weekly is currently estimated at US $55,250 per year.
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 following side effects are common (occurring in greater than 30%) for patients taking romiplostim: Headache fatigue Coughing up blood
These side effects are less common side effects (occurring in about 10-29%) of patients receiving romiplostim: Joint pain (arthralgia) Dizziness Insomnia Muscle pain (myalgia) Pain in extremity Abdominal pain Nausea Upper respiratory infection