Romiplostim Produces Durable Platelet Responses in Pediatric Patients with Immune Thrombocytopenia

Based on 2 randomized, placebo-controlled studies, the FDA approved romiplostim (Nplate) for pediatric patients 1 year and older with immune thrombocytopenia (ITP) for at least 6 months who do not have sufficient response to other treatments, including corticosteroids, splenectomy, and immunoglobulins.

ITP is a rare, hematologic disorder that is characterized by low platelet counts and impaired platelet production. Because of the low platelet counts, patients with ITP are at risk for spontaneous, major bleeding events, which could lead to hospitalization and death. Treatment for ITP involve maintaining a platelet count that reduces the risk of bleeding.

Some of the frequently used medications for ITP are corticosteroids, immunoglobulins, and other immune-suppressing drugs. Corticosteroids and immune-suppressing drugs, such as rituximab, have been used to prevent the immune system from damaging platelets, thus gradually increasing platelet count.

Immunoglobulins are given to increase blood counts quickly in situations where a major bleed had occurred. If these drugs are ineffective, a splenectomy is sometimes performed to remove the spleen. For children, a splenectomy is usually not done because they usually get better without treatment and not having a spleen predisposes to future infections.

Romiplostim is a thrombopoietin receptor agonist that increases platelet production. As the first platelet booster for chronic ITP in adults, romiplostim has just recently been approved by the FDA for use in pediatric patients 1 year and older with ITP for at least 6 months not responding to other treatment options. “In the 10 years since the FDA approved Nplate as the first platelet booster for adult patients with chronic ITP, it has made a difference in the lives of thousands of adults, and we're proud to bring this treatment option to children who need it most,” David M. Reese, MD, executive vice president of Research and Development at Amgen, said in a statement.¹

The approval of romiplostim was based on 2 double blind placebo-controlled trials: 1 phase 1/2 and 1 phase 3 trial. In the phase 1/2 trial (NCT00515203), 15 of the 17 patients who received romiplostim achieved a platelet count ≥50 x 10⁹/L and an increase in platelet count of ≥20 x 10⁹/L above their baseline for 2 consecutive weeks. In the phase 3 trial (NCT01444417), durable platelet response, defined as at least 6 weekly platelet counts ≥50 x 10⁹/L, occurred in 22 of the 42 patients (52%) who received romiplostim compared with 2 of the 20 patients (10%) who received placebo (P < .05). Overall platelet response occurred in 30 patients (71%) receiving romiplostim and 4 patients (20%) receiving placebo (P < .05).²

Common adverse events that occurred in ≥25% of the pediatric patients were contusion, upper respiratory tract infection, and oropharyngeal pain.^1,2

Current treatment options for pediatric patients with ITP remain limited due to the low prevalence of ITP in children. The “approval of Nplate offers new hope to the pediatric ITP community as it provides children with a new treatment option that may help to maintain safe platelet counts,” Michael D. Tarantino, MD, president of the Bleeding and Clotting Disorders Institute, said in a statement.¹

References

1. FDA approves Nplate (romiplostim) for use in pediatric patients with immune thrombocytopenia [news release]. Thousand Oaks, CA: Amgen; December 14, 2018. https://www.amgen.com/media/news-releases/2018/12/fda-approves-nplate-romiplostim-for-use-in-pediatric-patients-with-immune-thrombocytopenia/?rel=0" ?rel=0" ?rel=0" . Accessed January 16, 2018.

2. FDA approves romiplostim for pediatric patients with immune thrombocytopenia. US Food and Drug Administration. https://www.fda.gov/Drugs/InformationOnDrugs/ApprovedDrugs/ucm628525.htm?rel=0" . Published on December 14, 2018. Accessed on January 16, 2019.