Eltrombopag improves platelet engraftment after haploidentical bone marrow transplantation: Results of a Phase II study

Abstract Slow platelet recovery frequently occurs after haploidentical hematopoietic stem cell transplantation (haplo‐HSCT) with bone marrow graft and post‐transplant cyclophosphamide (PCy)‐based graft‐versus‐host disease (GVHD) prophylaxis. Improved platelet recovery may reduce the need for transfusions and improve outcomes. We investigated the safety and efficacy of eltrombopag, a thrombopoietin receptor agonist, at enhancing platelet recovery post‐haplo‐HSCT. The prospective study included patients ≥18 years of age who received haplo‐HSCT with bone marrow graft and PCy. Patients received eltrombopag 300 mg/day starting on Day +5. The primary objective was to estimate platelet engraftment (>50 000/μL by Day 60). In a post hoc analysis, they were compared to a contemporary matched control group who did not receive eltrombopag. One hundred ten patients were included in the analysis (30 eltrombopag and 80 control). Seventy‐three percent and 50% of patients in the eltrombopag group and control group, respectively, attained >50 000/μL platelet count by Day 60 ( p = .043). No eltrombopag‐related grade ≥4 adverse events were observed. Median time to platelet recovery (>20 000/μL) was 29 days with eltrombopag and 31 days for controls ( p = .022), while its cumulative incidence was 90% (95% confidence interval [CI]: 78%–100%) with eltrombopag versus 67.5% (95% CI: 57%–78%) for controls ( p = .014). Number of platelet transfusions received, overall survival, progression‐free survival, GVHD rate, relapse rate, and non‐relapse mortality were similar between groups. Overall, eltrombopag is safe and improves platelet recovery in patients undergoing haplo‐HSCT with bone marrow graft and PCy.