Nplate (romiplostim) Phase III study in children with symptomatic immune thrombocytopenia.-Amgen

Amgen has announced that The Lancet published results from a Phase III randomized, double-blind, placebo-controlled study of Nplate (romiplostim) in children with symptomatic immune thrombocytopenia (ITP). The study showed that 52 percent of Nplate patients achieved a durable platelet response, compared with 10 percent of placebo-treated patients (p=0.002, odds ratio 9.1, 95 percent CI: 1.9, 43.2). The study met the primary endpoint of durable platelet response and showed that children who were treated with Nplate had increased rates of overall platelet response, and patients who responded to Nplate maintained consistently elevated platelet counts.

These findings demonstrate that Nplate may be a potential treatment option for children with symptomatic ITP of more than six months duration. The most frequently reported adverse events (AEs) included contusion, epistaxis, headache and upper respiratory tract infections. The overall safety profile observed in the Nplate arm was similar to the known safety profile of Nplate. The treatment goal for children with ITP is to promote a platelet count that maintains appropriate control of bleeding,1 improve symptoms and increase the number of platelets.

This Phase III double-blind study randomized 62 children who have had ITP for more than six months to weekly Nplate or placebo (2:1) for 24 weeks. Durable platelet response, the primary endpoint of the study, was defined as achieving weekly platelet responses (increased platelets) without rescue medication in at least six of the final eight weeks. Secondary endpoints of the study included the evaluation of overall platelet response, the total number of weekly platelet responses, the use of ITP rescue medications, composite bleeding episodes and the overall safety of Nplate. Exploratory endpoints included the evaluation of bleeding incidence and changes in patient reported outcomes. Rescue medication was defined as any medication intended to increase platelet counts or prevent bleeding, and any increase in dose, frequency or additional therapy was categorized as rescue medication. Patients entering the study were permitted to use the same standard-of-care therapy, dose and schedule from when screening platelet counts were measured. By the final eight weeks of the study, noncutaneous bleeding had decreased with Nplate, and rates of durable platelet response were 52 percent compared to 10 percent with placebo (p=0.002, odds ratio 9.1, 95 percent CI: 1.9, 43.2). Rates of overall platelet response with Nplate were 71 percent (30/42) compared with 20 percent with placebo (p=0.0002, odds ratio 9.0, 95 percent CI: 2.5, 32.3), and rates of any platelet response were 81 percent (34/42) with Nplate compared to 55 percent (11/20) with placebo (p=0.0313).

Comment: Nplate was approved to treat thrombocytopenia in adults in the US in August 2008 and in the EU in February 2009.