Romiplostim in adult patients with newly diagnosed or persistent immune thrombocytopenia (ITP) for up to 1 year and in those with chronic ITP for more than 1 year: a subgroup analysis of integrated data from completed romiplostim studies

Abstract

The thrombopoietin receptor agonist romiplostim is approved for second-line use in chronic immune thrombocytopenia (ITP), but its effects in patients with ITP for ≤1 year are not well characterized. This analysis of pooled data from 9 studies included patients with ITP for ≤1 year (n = 311) or >1 year (n = 726) who failed first-line treatments and received romiplostim, placebo or standard of care. In subgroup analysis by ITP duration, patient incidences for platelet response at ≥75% of measurements were higher for romiplostim [ITP ≤1 year: 74% (204/277); ITP >1 year: 71% (450/634)] than for placebo/standard of care [ITP ≤1 year: 18% (6/34); ITP >1 year: 9% (8/92)]. Of patients with ≥9 months on study, 16% with ITP ≤1 year and 6% with ITP >1 year discontinued romiplostim and maintained platelet counts ≥50 × 109 /l for ≥6 months without ITP treatment (treatment-free remission). Independent of ITP duration, rates of serious adverse events and bleeding were lower with romiplostim than placebo/standard of care and thrombotic events occurred at similar rates. In this analysis, romiplostim and placebo/standard of care had similar safety profiles and romiplostim increased platelet counts in patients with either ITP ≤1 year or ITP >1 year, with more treatment-free remission in those with ITP ≤1 year.

Keywords: immune thrombocytopenia; newly diagnosed; persistent; romiplostim; thrombopoietin.

© 2019 The Authors. British Journal of Haematology published by British Society for Haematology and John Wiley & Sons Ltd.

Figures

Figure 1

Patient disposition by ITP duration. Patient flow is shown by ITP duration through both the parent study and extension study (for those patients who entered an extension study) with reasons for discontinuation. ITP, immune thrombocytopenia.

Figure 2

Platelet count over time (A) and platelet response (B) by ITP duration. (A) Median (Q1, Q3) platelet counts are shown for romiplostim‐treated patients by ITP duration at study baseline. (B) Proportion of patients meeting various platelet response measures by ITP duration at study baseline. Platelet response was defined as platelet counts ≥50 × 109/l, excluding platelet counts obtained in the 8 weeks after rescue medication use. Durable platelet response is defined as having a platelet response for ≥6 weeks of weeks 17–24 so as to allow time for dose titration and effects on thrombopoiesis. ITP, immune thrombocytopenia; PBO, placebo; ROM, romiplostim; Q1, quartile 1; Q3, quartile 3; SOC, standard of care.

Figure 3

Rescue medication use by ITP duration. Duration‐adjusted event rate of rescue medication use (per 100 patient‐years) is shown by ITP duration at study baseline for any rescue medication (A), corticosteroid rescue medication (B), and IVIg rescue medication (C). Rescue medications were ITP medications added by the investigator to treat or prevent bleeding and could include newly introduced ITP medications and dose/frequency increase of baseline ITP medications other than romiplostim. ITP, immune thrombocytopenia; IVIg, intravenous immunoglobulin; pt‐yr, patient‐year(s).

Figure 4

Bleeding over time by ITP duration. Duration‐adjusted bleeding (per 100 patient‐years) over time for romiplostim‐treated patients (A, C) and PBO/SOC patients (B, D) by ITP duration at baseline for both all‐grade (A, B) and grade ≥2 (C, D) bleeding. ITP, immune thrombocytopenia; PBO, placebo; PBO, placebo; pt‐yr, patient‐years; SOC, standard of care.

Figure 5

Thrombotic events in the romiplostim group by platelet count and ITP duration. Duration‐adjusted rates (per 100 patient‐years) are shown for thrombotic events by nearest previous platelet count in the previous 3 months. If a given patient had multiple thrombotic events at different platelet counts, then that patient could be counted in multiple platelet count categories. ITP, immune thrombocytopenia; pt‐yr, patient‐year(s).