Evaluation of Bleeding-Related Episodes in Patients with Chronic Immune Thrombocytopenic Purpura (ITP) Receiving Romiplostim or Medical Standard of Care.

Chronic ITP is an autoimmune disease characterized by low platelet counts and increased risk of bleeding that may be severe or even fatal. Rescue medications, most commonly intravenous immunoglobulins, are used to treat or prevent bleeding but produce only transient increases in platelet counts in most cases and may have issues with toxicity. Romiplostim is a peptibody protein designed to increase platelet production by binding to and activating the thrombopoietin receptor, and is approved for the treatment of adult chronic ITP.

To determine the effects of romiplostim treatment on bleeding outcomes during a phase 3b, randomized, open-label study, in adult nonsplenectomized ITP patients receiving either romiplostim or medical standard of care (SOC). We have developed a clinically-relevant composite endpoint, termed bleeding-related episode (BRE). A BRE was considered to be either an actual bleeding event, and/or the use of rescue medication to treat or prevent bleeding.

Patients were randomized (2:1) to romiplostim or SOC. Eligible patients were required to have either a platelet count <50×10⁹/L or have had their platelet count fall to <50×10⁹/L during or after a clinically-indicated taper or discontinuation of current ITP therapy. Once-weekly subcutaneous romiplostim was administered with dose adjustments to target a platelet count between 50 and 200 × 10⁹/L. SOC treatments were prescribed according to standard institutional practices or therapeutic guidelines. Since many types of ITP treatment could be administered in the SOC group, for the purpose of this analysis rescue medication was defined as any use of immunoglobulins (intravenous immunoglobulin or Anti-D), intravenous steroids, or platelet transfusions. In order to collapse related events into episodes, events (bleeding events and/or the use of rescue medication) that occurred concurrently or within 3 days of each other were considered a single clinical episode. Rates of BREs per 100 patient-weeks were calculated from the number of events/episodes divided by the number of patient-weeks on study treatment, multiplied by 100.

During the 52-week treatment period, the total number of patient-weeks for the romiplostim group (N=154) was 7087, and for the SOC group (N=70) was 2571. During the treatment period, the rate of BREs was lower in the romiplostim group than the SOC group (see Table), with a 67% reduction in the rate of BREs in patients receiving romiplostim compared to SOC (95% CI, 60% to 73%). The rate of BREs involving the use of immunoglobulins was also lower in the romiplostim group, with a 95% reduction in the rate of BREs in patients receiving romiplostim compared to those receiving SOC (95% CI, 92% to 97%).

Compared to SOC, romiplostim was associated with a reduction in all BREs as well as BREs involving immunoglobulin use.

Stasi:Amgen Inc.: Honoraria, Speakers Bureau; GlaxoSmithKline: Honoraria, Speakers Bureau. Giagounidis:Amgen Inc.: Consultancy, Speakers Bureau. Janssens:Roche: Honoraria. Legg:Amgen Inc.: Employment, Equity Ownership. Danese:Amgen Inc.: Consultancy, Research Funding. Deuson:Amgen Inc.: Employment, Equity Ownership.