Evaluation of Bleeding-Related Episodes in Patients with Chronic Immune Thrombocytopenia (ITP) Treated with Romiplostim in Two Phase 3 Placebo-Controlled Clinical Trials.

Chronic Immune thrombocytopenia (ITP) is characterized by low platelet counts and increased risk of bleeding. Rescue medications used to treat or prevent bleeding produce transient increases in platelet counts but may be associated with additional toxicities and costs. Romiplostim, approved for the treatment of adult chronic ITP, is a TPO mimetic peptibody protein that increases platelet production. Previously published data from phase 3 romiplostim trials showed that despite the increased use of rescue medication in the placebo arm, patient (pt) incidence of bleeding was reduced in the romiplostim arm vs placebo arm: 15% vs 34% (p = 0.02) for bleeding of grade ≥2 severity and 7% vs 12% (p=0.36) for grade ≥3 severity.

To evaluate the effects of romiplostim treatment on bleeding outcomes in the phase 3 placebo controlled studies in chronic ITP pts with and without previous splenectomy. Bleeding events were captured as adverse events making it difficult to identify a single event reported multiple times versus persistent or recurrent bleeding. Further, we have developed a composite endpoint, termed bleeding-related episodes (BREs), which combines bleeding events and rescue medication administration to account for use of rescue medications to prevent bleeding.

Adults with chronic ITP and a mean baseline platelet count <30 × 10⁹/L were eligible. The previously published studies were conducted separately in splenectomized and nonsplenectomized populations. Pts were randomized (2:1) to receive romiplostim or placebo by subcutaneous injection once weekly for 24 weeks, with dose adjustments to maintain platelet counts between 50-200 × 10⁹/L. Rescue medications were permitted to treat or prevent bleeding and included immunoglobulins, platelet transfusions, corticosteroids, or an increase in dose or frequency of a concurrent ITP medication. A BRE was defined as an actual bleeding event and/or the use of rescue medication. 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 BRE. Bleeding events beginning 7 or more days after the start of the initial bleeding event were considered a new BRE. To account for differences in time spent on-study, rates of BRE per 100 pt-weeks were calculated.

A total of 125 pts (41 placebo, 84 romiplostim) were enrolled in the two studies. Baseline characteristics were well-balanced between the placebo and romiplostim-treated groups. During the treatment period, the rate of BREs was lower in the romiplostim group than in the placebo group, and results were consistent between splenectomized and nonsplenectomized pts (Table). Across both studies, the rate of BREs was reduced by 55% in pts receiving romiplostim compared to those receiving placebo (95% CI, 41% to 65%). BREs were more frequent at platelet counts <50 × 10⁹/L (Table). BREs associated with hospitalizations were less common among romiplostim- than placebo-treated pts, and occurred at platelet counts <50 × 10⁹/L in 10 of 11 cases. Corticosteroids (58 romiplostim, 38 placebo) and immunoglobulins (30 romiplostim, 73 placebo), were the most commonly used rescue medications and the rate of BREs including immunoglobulins was reduced by 88% in pts receiving romiplostim compared to placebo.

In adults with chronic ITP, romiplostim was associated with a significant reduction in BREs compared to placebo. There was a marked reduction in BREs requiring immunoglobulins in the romiplostim arm compared to the placebo arm. Results were comparable in splenectomized and nonsplenectomized populations.

The platelet count for a BRE starting ≥1 day after a platelet count measurement was calculated from the 2 proximal weekly measurements.

Weitz:Amgen Inc.: Speakers Bureau. Sanz:Amgen Inc.: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Henry:Amgen Inc.: Research Funding, Speakers Bureau; Orthobiotech: Research Funding, Speakers Bureau; Watson Pharma: Research Funding, Speakers Bureau. Schipperus:Amgen Inc.: Membership on an entity's Board of Directors or advisory committees. Godeau:Amgen Inc.: Consultancy, Research Funding; Laboratoire Français de Fractionnement et de Biotechnologies (LFB): Consultancy; Roche: Research Funding. Gleeson:Amgen Inc.: Consultancy, Research Funding. Danese:Amgen Inc.: Consultancy, Research Funding. Deuson:Amgen Inc.: Employment, Equity Ownership.