Eltrombopag is an oral thrombopoietin‒receptor agonist (TPO-RA) that is approved for the treatment of previously treated patients with chronic immune thrombocytopenia (ITP). A phase 4, open-label safety study of eltrombopag assessed the bone marrow reticulin and collagen during eltrombopag treatment in patients with persistent or chronic ITP; the current post-hoc subgroup analysis sought to evaluate the effects of >2 years of eltrombopag treatment on platelet counts and long-term safety in adults with persistent or chronic ITP.

Eligible patients were adults aged ≥18 years diagnosed with persistent ITP (3-<12 months) or chronic ITP (≥12 months) who had not received any prior treatment with eltrombopag or romiplostim <6 months before screening. Eltrombopag was initiated at 50 mg/day or 25 mg (East Asian patients), with dose adjustments to a lower dose or maximum 75-mg dose as required to maintain platelet counts within the clinically indicated range.

Of the 162 patients enrolled in the current study, 37 (23%) had persistent ITP and 124 (77%) had chronic ITP. In the persistent ITP cohort, 8% of patients were splenectomized, 51% had platelets <30 × 109/L, and 100% had no prior TPO-RA exposure. In the chronic ITP cohort, 27% were splenectomized, 60% had platelets <30 × 109/L, and 90% had no prior TPO-RA exposure. Median duration of treatment exposure was 2.0 years (range, 31 days-2.1 years) in the persistent ITP cohort and 2.0 years (range, 21 days-2.2 years) in the chronic ITP cohort.

In both the persistent and chronic ITP cohorts, median platelet counts increased to ≥50 × 109/L within 1 week. A total of 31 (84%) patients with persistent ITP achieved a platelet count ≥50 × 109/L without rescue therapy, as did 109 (88%) patients with chronic ITP; 19 (51%) and 62 (50%) patients maintained platelet counts ≥50 × 109/L for ≥28 weeks. Among patients with baseline platelets <50 × 109/L who achieved platelet counts ≥50 × 109/L with eltrombopag treatment and no rescue therapy, the median time to platelets ≥50 × 109/L was 4.0 (95% confidence interval [CI], 1.3-14.4) weeks in the persistent ITP cohort (n = 25) and 2.1 (95% CI, 1.4-2.1) weeks in the chronic ITP cohort (n = 99). Rescue therapy was administered in 16 (43%) patients in the persistent ITP cohort and 50 (40%) patients in the chronic ITP cohort.

Treatment-emergent adverse events were experienced by 32 (86%) patients in the persistent ITP cohort and 108 (87%) patients in the chronic ITP cohort; serious adverse events occurred in 12 (32%) and in 29 (23%) patients, respectively. Serious adverse events in the persistent ITP cohort included nausea (n = 2) and fatigue (n = 2); serious adverse events in the chronic ITP cohort included gastrointestinal hemorrhage, gingival bleeding, tooth abscess, cerebral hemorrhage, lethargy, thrombocytopenia, and menorrhagia in 2 patients each. Three patients with chronic ITP died (cerebral hemorrhage [n = 2] and acute respiratory distress syndrome [n = 1]); no deaths were reported in the persistent ITP cohort.

The authors concluded that effects of >2 years of eltrombopag treatment on platelet counts was comparable between the persistent ITP and the chronic ITP cohorts, with similar safety profiles.

Wong R, et al. ASH 2017. Abstract 3628.

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Last modified: December 28, 2017