Amgen Inc. (Nasdaq: AMGN) today announced results from its first Phase 1/2 study evaluating the safety and efficacy of Nplate
® (romiplostim) in children with chronic immune thrombocytopenic purpura (ITP). Chronic ITP is a serious autoimmune disorder characterized by low platelet counts in the blood (thrombocytopenia), which can lead to serious bleeding events. The data were presented as an oral presentation at the 2009 American Society of Hematology
(ASH) Annual Meeting and Exposition (ASH Abstract #680). Additionally, updated five-year follow-up results from an ongoing, open-label extension study in adults were presented and add to the data available on the long-term efficacy and safety of Nplate in adult patients with chronic ITP (ASH Abstract #681).
Results from Phase 1/2 Study in Children (Abstract #680)
ITP in children most commonly presents as an acute illness; however, 20-30 percent of these cases will persist as chronic ITP (duration over six months). Results of the study showed that treatment with Nplate appeared to be generally well-tolerated compared to placebo in children (aged 12 months to less than 18 years old) with chronic ITP (treatment related adverse events = 18 percent vs. 20 percent, respectively).
"Currently, most drug treatment options for children with chronic ITP involve immunosuppression," said Dr. George R. Buchanan, professor of Pediatrics at the University of Texas Southwestern Medical Center at Dallas. "This is the first study of an agent that stimulates platelet production in the pediatric population. The results suggest that Nplate could potentially be an important treatment option for selected children suffering from chronic ITP."
Safety results of the study showed that adverse event rates were similar between those patients treated with Nplate or placebo with most adverse events being mild to moderate in severity. Most frequent adverse events in patients taking Nplate or placebo were headache (35 percent vs. 40 percent, respectively), epistaxis (35 percent vs. 20 percent, respectively), cough (12 percent vs. 40 percent, respectively) and vomiting (12 percent vs. 40 percent, respectively).
Efficacy results showed that Nplate was effective in treating thrombocytopenia compared to placebo, with 88 percent of the 17 patients receiving Nplate achieving both efficacy endpoints during treatment (number of patients achieving a platelet count of over 50,000 platelets per microliter for two consecutive weeks during the treatment period and/or achieving an increase in the platelet count of 20,000 platelets per microliter above baseline for two consecutive weeks). Other observations included a decrease in rescue medication use, and numerically lower duration-adjusted bleeding adverse event rates with Nplate treatment as compared with placebo. None of the placebo-treated patients>
This Phase 1/2, 12-week treatment period evaluated the safety and efficacy of Nplate in the treatment of thrombocytopenia in children with chronic ITP>
Results from Ongoing, Long-Term Extension Efficacy and Safety Study (Abstract #681)
Results from an ongoing, long-term extension study in adults that were also presented at the meeting showed that Nplate maintained platelet counts within a range of 50,000 to 200,000 platelets per microliter in the majority of adult patients with chronic ITP with minimal dose adjustments for up to nearly five years. Over the course of the study, a platelet count of greater than or equal to 50,000 platelets per microliter was achieved by 94 percent of 291 patients receiving Nplate, and the median platelet count remained greater than or equal to 50,000 platelets per microliter for the duration of the study after Week 1.
Patients were treated for a median of 48 weeks with a maximum duration of 244 weeks>
"This updated five-year data represents the longest adult chronic ITP study ever conducted and the findings add to the data available on the long-term efficacy and safety of Nplate," said David J. Kuter, M.D., Chief of Hematology, Massachusetts General Hospital, Boston.
In addition, results showed that treatment with Nplate was generally well-tolerated and adverse event rates did not increase with longer duration of treatment. Of the 37 patients receiving concurrent ITP treatment (i.e., corticosteroids, IVIG, Win-Rho, Anti-D therapy), 78 percent were able to discontinue or reduce their dose of Nplate by more than 25 percent. Home administration of Nplate was achieved by 75 percent of patients.
This is an ongoing, open-label, long-term efficacy and safety study of Nplate for the treatment of patients with chronic ITP. Nplate was administered once weekly by subcutaneous injection, with dose adjustments to maintain platelet counts in the target range (50,000 to 200,000 platelet count per microliter). The primary study objective was to determine long-term safety of Nplate. Secondary study objectives were to evaluate long-term platelet responses and the use of concurrent ITP therapies.