NPLATE

What it is

Nplate contains the active ingredient, romiplostim. It is supplied as a sterile, preservative-free, lyophilised white powder in single dose glass vials for reconstitution and subcutaneous (SC) injection. Romiplostim increases platelet production through binding and activation of the thrombopoietin receptor, a mechanism analogous to endogenous thrombopoietin.

Approved indications

Adults: Nplate is indicated for treatment of thrombocytopenia in adult patients with primary immune thrombocytopenia (ITP) who are non-splenectomised and have had an inadequate response, or are intolerant, to corticosteroids and immunoglobulins, or who are splenectomised and have had an inadequate response to splenectomy. Paediatrics: Nplate is indicated for treatment of thrombocytopenia in paediatric patients aged 1 year and older with primary immune thrombocytopenia for at least 6 months who are non-splenectomised and have had an insufficient response, or are intolerant, to corticosteroids and immunoglobulins, or who are splenectomised and have had an inadequate response to splenectomy.

Dosing overview

Use the lowest dose of Nplate necessary to achieve and maintain a platelet count ≥50×10⁹/L. Administer Nplate as a weekly subcutaneous injection, with dose adjustments based upon the platelet count response. The recommended initial dose for Nplate is 1 μg/kg, based on actual patient's body weight. Adjust the weekly dose of Nplate in increments of 1 μg/kg until the patient achieves a platelet count between 50×10⁹/L to ≤200×10⁹/L. Do not exceed a maximum weekly dose of 10 μg/kg.

Key safety warnings

Thrombocytopenia is likely to recur upon discontinuation of Nplate; some patients may develop thrombocytopenia of greater severity than was present prior to Nplate. There is increased risk for bleeding if Nplate is discontinued in the presence of anticoagulants or anti-platelet agents. Patients should be closely monitored for a decrease in platelet count and medically managed to avoid bleeding upon discontinuation of Nplate. Serious life-threatening or fatal bleeding events after discontinuation of Nplate have been reported. Reticulin has been observed in the bone marrow of some ITP patients prior to treatment with Nplate and appeared to increase in some patients treated with Nplate. Increased bone marrow reticulin is believed to be due to the increased number of megakaryocytes in the bone marrow which may subsequently release cytokines. Thrombotic/thromboembolic events including deep vein thrombosis, pulmonary embolism, and myocardial infarction have been observed with the use of romiplostim in the ITP population. These events have occurred regardless of platelet count. Cases of thromboembolic events including portal vein thrombosis have been reported in patients with chronic liver disease receiving Nplate. Nplate should be used with caution in this population. There is a theoretical concern that romiplostim may stimulate the progression of existing myeloid malignancies or MDS. In clinical studies of treatment with Nplate in adult patients with MDS, cases of progression to acute myeloid leukaemia (AML), a potential clinical outcome of MDS, were reported. In addition, there were cases of transient blast cell increases, which did not progress to AML.

Contraindications

Nplate is contraindicated in patients with known hypersensitivity to E. coli-derived products, romiplostim, or any other product ingredient.

PBS listing

Nplate is listed on the PBS in two strengths: powder for injection 375 micrograms and powder for injection 625 micrograms. Both strengths have authority required restriction, with ex-manufacturer prices of A$494.12 and A$988.24 respectively.

Regulatory history

Nplate was first registered on the ARTG on 8 August 2008, with registration of the 375 microgram and 625 microgram powder for injection vials. The 230 microgram powder for injection vial was registered on 23 October 2017. Nplate is subject to additional monitoring in Australia. This will allow quick identification of new safety information.