October 18, 2019
The U.S. FDA has approved an update to the label for Amgen’s Nplate® (romiplostim). The label now includes new data demonstrating sustained platelet responses in adults who have immune thrombocytopenia (ITP). In addition, the FDA has approved an expanded indication for Nplate to treat adult patients with newly diagnosed or persistent ITP that has had an insufficient response to treatment with corticosteroids, immunoglobulins, or splenectomy (surgical removal of the spleen).
ITP is a rare disorder in which the body’s immune system creates antibodies that attack and destroy healthy blood platelets required for normal blood clotting. At the same time, the body may produce antibodies that affect the bone marrow and cause it to produce fewer platelets than normal. The result is a shortage of blood platelets (thrombocytopenia), which can lead to abnormal bleeding. ITP can occur on its own, following viral or bacterial infection, or as a complication of other immune or blood disorders.
In a clinical trial, 32% of patients who received Nplate shortly after demonstrating an insufficient response to first-line steroid therapy remained in remission for at least six months without any further ITP therapy. The ability to administer Nplate earlier in the course of disease may reduce the need for prolonged steroid use. In addition, patients treated with Nplate experienced a median 11 months with platelet response during a 12-month treatment period, and a median time to first platelet response of 2.1 weeks. Almost all patients (93%) achieved one or more platelet responses during the treatment period.
Recommended dosing for adult and pediatric patients with ITP is 1mcg/kg of body weight once weekly to begin, administered via subcutaneous (SC) injection. Dosing should be adjusted as necessary until the patient achieves a platelet count of at least 50×109/L, which reduces the risk of bleeding. The weekly dose should not exceed 10mcg/kg. In pediatric patients, body weight should be reassessed for dose adjustment once every 12 weeks. Nplate should be discontinued in patients of any age if the platelet count does not increase to a level sufficient to avoid clinically important bleeding after four weeks of therapy at the maximum weekly dose of 10mcg/kg. The product must be administered by a healthcare professional.
First FDA approved in 2008, Nplate was originally indicated for later stage treatment of ITP, and receive an additional indication to treat pediatric patients in 2018. The drug must be obtained through a Risk Evaluation and Mitigation Strategy (REMS) program known as Nplate NEXUS (Network of Experts Understanding and Supporting Nplate and Patients) due to a risk of severe side effects.