Avatrombopag for the treatment of thrombocytopenia post hematopoietic stem-cell transplantation.

Background: Thrombocytopenia post hematopoietic stem-cell transplantation (HCT) usually contributes to poor outcomes with no standardized treatment. Eltrombopag and romiplostim can be feasible for post-HCT thrombocytopenia, but the use of avatrombopag has not yet been evaluated.

Objectives: We aimed to evaluate the efficacy and safety of avatrombopag treatment in patients diagnosed with post-HCT thrombocytopenia.

Design: In this retrospective study, we evaluated the efficacy and safety of avatrombopag treatment in a cohort of 61 patients diagnosed with thrombocytopenia post HCT in our clinical center.

Methods: Avatrombopag was initiated at 20 mg daily, with a dosage adjustment to achieve platelet recovery to >20 × 10/l independent from transfusion for 7 consecutive days (overall response, OR) or to >50 × 10/l free from transfusion for 7 consecutive days (complete response, CR). Factors influencing OR and CR were studied in univariate and multivariate analyses, respectively. Within the follow-up, adverse events like myelofibrosis, thrombosis, and organ toxicities were monitored carefully.

Results: The overall response rate (ORR) to avatrombopag was 68.9% and the cumulative incidence (CI) of OR was 69.1%. The complete response rate (CRR) and the CI of CR were both 39.3%. The median days from avatrombopag initiation to OR and CR were 21 and 25 days, respectively. An adequate number of megakaryocytes before the initiation of avatrombopag was an independent protective factor of avatrombopag treatment for OR (hazard ratio, HR = 4.628, 95% confidence interval 1.92-11.15,  = 0.0006) and CR (HR = 4.892, 95% confidence interval 1.58-15.18,  = 0.006). Avatrombopag was well tolerated in all patients with no severe adverse events.

Conclusion: Our findings suggested that avatrombopag can be optional for thrombocytopenia post HCT.