Romiplostim for the treatment of chronic immune (idiopathic) thrombocytopenic purpura.

PURPOSE: On August 22, 2008, Romiplostim (Nplate for Injection) received approval from the US Food and Drug Administration (FDA) for the treatment of thrombocytopenia in patients with chronic immune (idiopathic) thrombocytopenic purpura (ITP) who have had an insufficient response to corticosteroids, immunoglobulins, or splenectomy. This report summarizes the FDA analyses of the clinical data supporting this approval.

EXPERIMENTAL DESIGN: The FDA reviewed data from two double-blind, placebo-controlled clinical studies, an uncontrolled extension study, and supportive studies. In the controlled studies, enrolled patients had completed at least one prior treatment for chronic ITP and had a platelet count < or = 30 x 10(9)/L. One study enrolled patients who had undergone splenectomy; the other enrolled patients who had not undergone splenectomy. The primary endpoint in both controlled studies was durable platelet response.

RESULTS: Overall, 125 patients were randomized in the controlled studies. A durable platelet response was observed in 61% of nonsplenectomized patients and 38% of patients who had undergone splenectomy. One placebo group patient achieved a durable platelet response. Serious hemorrhage events were reported in 10% of placebo recipients and 6% of romiplostim recipients. In the extension study, patients received romiplostim for a median of 60 weeks and a maximum of 96 weeks; the majority of patients maintained platelet counts > or = 50 x 10(9)/L throughout the study. Major safety findings pertained to a risk for bone marrow reticulin formation and worsened thrombocytopenia following romiplostim discontinuation.

CONCLUSIONS: The FDA approved romiplostim for use among certain patients with chronic ITP. This approval included a Risk Evaluation and Mitigation Strategy to ensure that the benefits of the drug outweigh its risks.