Amgen Inc. (Nasdaq: AMGN) today announced the final results from a 5-year open-label extension study investigating the long-term efficacy and safety of Nplate® (romiplostim) in adult chronic immune (idiopathic) 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 complete data, presented as an oral presentation at the 52nd Annual Meeting and Exposition of the American Society of Hematology (ASH), demonstrated that Nplate safely and effectively maintained platelet counts in the significant majority of patients for the duration of the study (Abstract #68).
"In this study, nearly all Nplate-treated patients were able to maintain platelet counts within the target range for more than five years," said David J. Kuter, M.D., chief of Hematology, Massachusetts General Hospital, Boston and lead investigator. "The most common and serious adverse events were consistent with those reported in past studies and did not increase over time. These results, from the largest and longest interventional study of TPO-mimetic exposure to date, provide physicians and their patients with important information on the continued long-term safety and efficacy of Nplate."
In the long-term extension study, 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 decreased or increased dose adjustments for up to 277 weeks. Over the course of the study, a platelet count of greater than or equal to 50,000 platelets per microliter was achieved by 95 percent of 292 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 one. Patients were treated for a median of 78 weeks with a maximum duration of 277 weeks and 33 percent of patients had previously undergone splenectomy.
In addition, results showed that adverse event rates in patients treated with Nplate were consistent with those reported in previous studies and did not increase with longer duration of treatment. The most common side effects were mild and included headache (38 percent), nasopharyngitis (34 percent) and fatigue (32 percent). Of the 37 patients who received concurrent ITP treatment at baseline, 81 percent were able to discontinue or reduce the dose by more than 25 percent.
This is an 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.