On October 18, the U.S. Food and Drug Administration (FDA) approved a supplemental biologics license application (sBLA) for romiplostim (Nplate) to include new data in its U.S. prescribing information showing sustained platelet responses in adults with immune thrombocytopenia. The updated indication expands treatment with romiplostim to newly diagnosed and persistent adult patients with immune thrombocytopenia who have had an insufficient response to corticosteroids, immunoglobulins, or splenectomy. In December of last year, the FDA approved another sBLA for romiplostim in the treatment of pediatric patients with immune thrombocytopenia.
Immune thrombocytopenia is an autoimmune disease characterized by low platelet counts in the blood and impaired platelet production. In the United States, the estimated incidence of immune thrombocytopenia is 6.1 per 100,000 adults annually, and nearly 20,000 people are newly diagnosed with immune thrombocytopenia each year.
Romiplostim is a thrombopoietin receptor agonist that mimics the body's natural thrombopoietin and is designed to increase platelet counts in patients with immune thrombocytopenia.
The sBLA was based on an open-label, single-arm phase II trial of adults with immune thrombocytopenia diagnosed ≤ 6 months prior who had an insufficient response to first-line treatment, including corticosteroids (n = 75). The median time from immune thrombocytopenia diagnosis to study enrollment was 2.2 months. On the primary endpoint, the median number of months with platelet response (≥ 50 x 109/L) was 11 months during the 12-month treatment period (95% confidence interval [CI] = 10–11), with a median time to first platelet response of 2.1 weeks (95% CI = 1.1–3.0). Additionally, 93% of patients achieved one or more platelet responses during the 12-month treatment period. Thirty-two percent of patients achieved remission for at least 6 months, defined by maintaining a platelet count ≥ 50 x 109/L in the absence of romiplostim and any medication for immune thrombocytopenia (concomitant or rescue).
The safety profile of romiplostim was similar across patients, regardless of immune thrombocytopenia duration. The following adverse reactions (at least 5% incidence and at least 5% more frequent with romiplostim compared with placebo or standard of care) occurred in patients with immune thrombocytopenia duration up to 12 months treated with romiplostim: bronchitis, sinusitis, vomiting, arthralgia, myalgia, headache, dizziness, diarrhea, upper respiratory tract infection, cough, nausea, and oropharyngeal pain. Thrombocytosis occurred in 2% of adults with immune thrombocytopenia duration up to 12 months.