Eltrombopag in the Treatment of Post Allogeneic Hematopoietic Stem Cell Transplantation Cytopenia: Efficacy, Response Durability and Potential Cost Benefit of Early Drug Tapering.

Introduction and Objectives The utilization of Eltrombopag (EPAG) in the management of Post Allogenic Hematopoietic Stem Cell Transplant (HSCT) cytopenia has exhibited promising outcomes. Isolated thrombocytopenia and Poor Graft Function (PGF) are factors that adversely influence transplant outcomes and patient well-being. This study aims to assess EPAG efficacy in this context as a primary outcome, and evaluate early EPAG tapering post complete response (CR) for cost-efficiency and response durability. Methods In this retrospective study, we enrolled 39 patients (69.2% male) with a median age at transplant of 61.0 years (Range: 23-73y) who underwent Allogenic HSCT. Among these, 89.7% (n=35) received EPAG for PGF, while 10.3% (n=4) were treated for isolated thrombocytopenia (primary or secondary).The median treatment duration was 16.3 weeks (Range: 4.4-120.1 weeks). EPAG was initiated at 50 mg daily dose and escalated to a maximum of 150 mg daily. Complete Response (CR) was defined as a sustained platelet count ≥ 50 × 109/L, Hb ≥100 g/L, and ANC ≥ 1.5 × 109/L without transfusions or growth factor support. Partial response (PR) was defined as platelet count 20–50 × 109/L or Hb 7–10 g/L or ANC 0.5–1.5 × 109/L. Early EPAG tapering was defined as start of tapering after 4 weeks of achieving CR. The pre-EPAG cost estimate included supportive care expenses (transfusion costs and hospital admissions due to cytopenia-related complications), Post-EPAG costs included the drug cost (50 mg pill costs 130 CAD) plus supportive care expenses. Results With a median follow up time of 12.4 months (range 2.4-46.9) the ORR of EPAG treatment was 71.8% (n=28), with 48.7% (n=19) achieving CR, and 23.1% (n=9) PR. The median response for platelets, hemoglobin and neutrophils were 2.71, 2.65, 2.00 weeks, respectively. Median duration between CR to EPAG tapering was 1.00 week (Range 0-18.3) with 10/19 responders being tapered earlier than 4 weeks of CR. All patients had a durable responses after stopping the drug. Median adjusted post EPAG cost in early tapering was significantly lower than actual post EPAG cost (p=0.01). There was no significant difference among median adjusted post EPAG cost in early tapering compared to total cost pre-EPAG (p=0.80). A limitation of our study is that we did not calculate the values of patient quality of life and health system costs. Conclusion EPAG demonstrates promise as a potential safe treatment for PGF and isolated thrombocytopenia post allogeneic HSCT. implementing early tapering of EPAG could be a safe and cost beneficial approach given the high drug cost and durable responses after stopping the drug.